2024-03-28T11:48:16Zhttps://vtechworks.lib.vt.edu/server/oai/requestoai:vtechworks.lib.vt.edu:10919/496542020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Sitepu, H.
author
2008-03
Phase transformation temperatures of a polycrystalline Ni-rich Ti49.86Ni50.14 shape memory alloy were investigated using a differential scanning calorimeter. In situ structural and texture analyses of the monoclinic Ti49.86Ni50.14 were investigated using neutron powder diffractometer technique. Differential scanning calorimeter results showed that this Ni-rich alloy has a one-step cubic to monoclinic martensitic phase transformation on cooling and a one-step monoclinic to cubic transformation on heating. In situ high-resolution neutron powder diffraction data of the monoclinic phase from low temperatures to room temperature on heating are consistent with the differential scanning calorimeter's heating results. In addition, the refined monoclinic crystal structure parameters for all neutron diffraction data sets agree satisfactorily with single-crystal X-ray diffraction results. The multiple-data-set capabilities of the GSAS Rietveld refinement program, with a generalized spherical-harmonics description was used successfully to extract the texture description directly from a simultaneous refinement using 52 time-of-flight monoclinic neutron diffraction patterns, taken from a polycrystalline sample held in 13 orientations inside the diffractometer. (c) 2008 International Centre for Diffraction Data.
Sitepu, H., "In situ structural and texture analyses of monoclinic phase for polycrystalline Ni-rich T49.86Ni50.14 alloy from neutron diffraction data," Powder Diffr., Vol. 23(1), 2008. DOI: 10.1154/1.2839141
0885-7156
http://hdl.handle.net/10919/49654
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8490189&fulltextType=RA&fileId=S0885715600000634
https://doi.org/10.1154/1.2839141
neutron powder diffraction
texture
martensitic phase transformation
ti49.86ni50.14 shape memory alloy
differential scanning calorimeter
shape-memory alloy
preferred orientation
rietveld refinement
crystal-structure
martensite
spectra
tini
materials science, characterization & testing
In situ structural and texture analyses of monoclinic phase for polycrystalline Ni-rich T49.86Ni50.14 alloy from neutron diffraction data
oai:vtechworks.lib.vt.edu:10919/932492021-06-21T19:11:44Zcom_10919_8195com_10919_25799com_10919_24209com_10919_5553col_10919_79698col_10919_24267
00925njm 22002777a 4500
dc
Steele-MacInnis, Matthew
author
Han, Liang
author
Lowell, Robert P.
author
Rimstidt, J. Donald
author
Bodnar, Robert J.
author
2012-05-13
Results of a numerical modeling study of quartz dissolution and precipitation in a sub-seafloor hydrothermal system have been used to predict where in the system quartz could be deposited and potentially trap fluid inclusions. The spatial distribution of zones of quartz dissolution and precipitation is complex, owing to the fact that quartz solubility depends on many inter-related factors, including temperature, fluid salinity and fluid immiscibility, and is further complicated by the fact that quartz exhibits both prograde and retrograde solubility behavior, depending on the fluid temperature and salinity. Using the PVTX properties of H2O-NaCl, the petrographic and microthermometric properties of fluid inclusions trapped at various locations within the hydrothermal system have been predicted. Vapor-rich inclusions are trapped as a result of the retrograde temperature-dependence of quartz solubility as the convecting fluid is heated in the vicinity of the magmatic heat source. Coexisting liquid-rich and vapor-rich inclusions are also trapped in this region when quartz precipitates as a result of fluid immiscibility that lowers the overall bulk quartz solubility in the system. Fluid inclusions trapped in the shallow subsurface near the seafloor vents and in the underlying stockwork are liquid-rich with homogenization temperatures of 200–400°C and salinities close to that of seawater. Volcanogenic massive sulfide (VMS) deposits represent the uplifted and partially eroded remnants of fossil submarine hydrothermal systems, and the relationship between fluid-inclusion properties and location within the hydrothermal system described here can be used in exploration for VMS deposits to infer the direction towards potential massive sulfide ore.
http://hdl.handle.net/10919/93249
https://doi.org/10.2478/s13533-011-0053-z
4
2
seafloor hydrothermal systems
volcanogenic massive sulfide deposits
silica
quartz veins
fluid inclusions
Quartz precipitation and fluid inclusion characteristics in sub-seafloor hydrothermal systems associated with volcanogenic massive sulfide deposits
oai:vtechworks.lib.vt.edu:10919/1159792023-08-04T07:11:59Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Irving, J. C. E.
author
Lekic, V.
author
Durán, C.
author
Drilleau, M.
author
Kim, D.
author
Rivoldini, A.
author
Khan, A.
author
Samuel, H.
author
Antonangeli, D.
author
Bruce Banerdt, W.
author
Beghein, C.
author
Bozdagk, E.
author
Ceylan, S.
author
Charalambous, C.
author
Clinton, J.
author
Davis, P.
author
Garcia, R.
author
Giardini, D.
author
Catherine Horleston, A.
author
Huang, Q.
author
Hurst, K. J.
author
Kawamura, T.
author
King, Scott D.
author
Knapmeyer, M.
author
Li, J.
author
Lognonné, P.
author
Maguire, R.
author
Panning, M. P.
author
Plesa, A. C.
author
Schimmel, M.
author
Schmerr, N. C.
author
Stählerc, S. C.
author
Stutzmann, E.
author
Xu, Z.
author
2023-05-02
We present the first observations of seismic waves propagating through the core of Mars. These observations, made using seismic data collected by the InSight geophysical mission, have allowed us to construct the first seismically constrained models for the elastic properties of Mars core. We observe core-Transiting seismic phase SKS from two farside seismic events detected on Mars and measure the travel times of SKS relative to mantle traversing body waves. SKS travels through the core as a compressional wave, providing information about bulk modulus and density. We perform probabilistic inversions using the core-sensitive relative travel times together with gross geophysical data and travel times from other, more proximal, seismic events to seek the equation of state parameters that best describe the liquid iron-Alloy core. Our inversions provide constraints on the velocities in Mars core and are used to develop the first seismically based estimates of its composition. We show that models informed by our SKS data favor a somewhat smaller (median core radius = 1,780 to 1,810 km) and denser (core density = 6.2 to 6.3 g/cm3) core compared to previous estimates, with a P-wave velocity of 4.9 to 5.0 km/s at the core mantle boundary, with the composition and structure of the mantle as a dominant source of uncertainty. We infer from our models that Mars core contains a median of 20 to 22 wt% light alloying elements when we consider sulfur, oxygen, carbon, and hydrogen. These data can be used to inform models of planetary accretion, composition, and evolution.
0027-8424
http://hdl.handle.net/10919/115979
https://doi.org/10.1073/PNAS.2217090120
120
118
King, Scott [0000-0002-9564-5164]
37094138
1091-6490
Mars
core evolution
planetary structure
First observations of core-transiting seismic phases on Mars
oai:vtechworks.lib.vt.edu:10919/1044592021-07-31T07:10:48Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Rajaonarison, Tahiry A.
author
Stamps, D. Sarah
author
Naliboff, John
author
2021-03-28
Despite decades of investigation, the origin of forces driving continental rifting remains highly debated. Deciphering their relative contributions is challenging due to the nonlinear and depth-dependent nature of lithospheric rheology. Recent geodynamic studies of the East African Rift (EAR) report contradicting results regarding the relative contribution of horizontal mantle tractions and lithospheric buoyancy forces. Here, we use high-resolution 3D regional numerical modeling of the EAR to isolate the contribution lithospheric buoyancy forces to observed deformation. Modeled surface velocities closely match kinematic models of the Somalian Plate, Victoria Block, and Rovuma Block motions, but provide poor fit to along-rift surface motions in deforming zones. These results suggest that lithospheric buoyancy forces primarily drive present-day similar to E-W extension across the EAR, but intrarift deformation may result from viscous coupling to horizontal asthenospheric flow.
0094-8276
e2020GL090483
http://hdl.handle.net/10919/104459
https://doi.org/10.1029/2020GL090483
48
6
1944-8007
East African Rift
geodynamics
gravitational potential energy
lithospheric buoyancy forces
lithospheric deformation
surface motion
Role of Lithospheric Buoyancy Forces in Driving Deformation in East Africa From 3D Geodynamic Modeling
oai:vtechworks.lib.vt.edu:10919/767002023-11-29T19:06:47Zcom_10919_5540com_10919_24209com_10919_5553col_10919_71752col_10919_24267
00925njm 22002777a 4500
dc
Madrigal, Pilar
author
Gazel, Esteban
author
Flores, Kennet E.
author
Bizimis, Michael
author
Jicha, Brian
author
2016-11-08
Large igneous provinces, as the surface expression of deep mantle processes, play a key role in the evolution of the planet. Here we analyse the geochemical record and timing of the Pacific Ocean Large Igneous Provinces and preserved accreted terranes to reconstruct the history of pulses of mantle plume upwellings and their relation with a deep-rooted source like the Pacific large low-shear velocity Province during the Mid-Jurassic to Upper Cretaceous. Petrological modelling and geochemical data suggest the need of interaction between these deep-rooted upwellings and mid-ocean ridges in pulses separated by ∼10–20 Ma, to generate the massive volumes of melt preserved today as oceanic plateaus. These pulses impacted the marine biota resulting in episodes of anoxia and mass extinctions shortly after their eruption.
http://hdl.handle.net/10919/76700
https://doi.org/10.1038/ncomms13309
7
Record of massive upwellings from the Pacific large low shear velocity province
oai:vtechworks.lib.vt.edu:10919/254032020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Waeselmann, N.
author
Maier, B. J.
author
Mihailova, B.
author
Angel, Ross J.
author
Zhao, J.
author
Gospodinov, M.
author
Paulmann, C.
author
Ross, Nancy L.
author
Bismayer, U.
author
2012-01-17
Pressure-induced structural transformations in relaxor-based perovskite-type (ABO(3)) 0.9PbZn(1/3)Nb(2/3)O(3)-0.1PbTiO(3) single crystals which have a very high piezoelectric response were studied by single-crystal x-ray diffraction and Raman spectroscopy at room temperature and pressures up to 18.1 GPa. Changes in the state of long-range order were observed near 1.0, 2.1, and 5.9 GPa. Initially, upon pressure increase, the ferroic deviation of the atomic positions from the cubic structure is reduced, but the ferroelectric twinning is enhanced, and near 1.0 GPa, the intrinsic ferroelectric multiphase domain pattern formed in the as-synthesized crystals is changed. At 2.1 GPa, the system undergoes a phase transition from a ferroelectric to a relaxor state, which exhibits an average cubic structure but still contains polar nanoregions. At 5.9 GPa, a reversible phase transition typical of Pb-based perovskite-type relaxors occurs, namely a cubic-to-antiferrodistortive phase transition resulting in a long-range order of antiphase octahedral tilts. On decompression, the ferroelectric state reappears below 2.1 GPa, and the local atomic structure is fully recovered at ambient pressure, but the final domain texture differs from the initial one. Ruthenium doping on the B site does not influence the pressure-induced structural transformations.
Waeselmann, N. ; Maier, B. J. ; Mihailova, B. ; et al., Jan 17, 2012. "Pressure-induced structural transformations in pure and Ru-doped 0.9PbZn(1/3)Nb(2/3)O(3)-0.1PbTiO(3) near the morphotropic phase boundary," PHYSICAL REVIEW B 85(1): 014106. DOI: 10.1103/PhysRevB.85.014106
1098-0121
http://hdl.handle.net/10919/25403
http://link.aps.org/doi/10.1103/PhysRevB.85.014106
https://doi.org/10.1103/PhysRevB.85.014106
ferroelectric single-crystals
relaxor ferroelectrics
piezoelectric
properties
perovskites
Physics
Pressure-induced structural transformations in pure and Ru-doped 0.9PbZn(1/3)Nb(2/3)O(3)-0.1PbTiO(3) near the morphotropic phase boundary
oai:vtechworks.lib.vt.edu:10919/1104552022-06-08T07:11:56Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Yang, Yu
author
Zeng, Zuoxun
author
King, Scott D.
author
Shuang, Xiao
author
2022-07
The Pamir-Hindu Kush region at the western end of the Himalayan-Tibet orogen is one of the most active regions on the globe with strong seismicity and deformation and provides a window to evaluate conti-nental collision linked to two intra-continental subduction zones with different polarities. The seismicity and seismic tomography data show a steep northward subducting slab beneath the Hindu Kush and southward subducting slab under the Pamir. Here, we collect seismic catalogue with 3988 earthquake events to compute seismicity images and waveform data from 926 earthquake events to invert focal mechanism solutions and stress field with a view to characterize the subducting slabs under the Pamir-Hindu Kush region. Our results define two distinct seismic zones: a steep one beneath the Hindu Kush and a broad one beneath the Pamir. Deep and intermediate-depth earthquakes are mainly distributed in the Hindu Kush region which is controlled by thrust faulting, whereas the Pamir is domi-nated by strike-slip stress regime with shallow and intermediate-depth earthquakes. The area where the maximum principal stress axis is vertical in the southern Pamir corresponds to the location of a high-conductivity low-velocity region that contributes to the seismogenic processes in this region. We inter-pret the two distinct seismic zones to represent a double-sided subduction system where the Hindu Kush zone represents the northward subduction of the Indian plate, and the Pamir zone shows southward sub-duction of the Eurasian plate. A transition fault is inferred in the region between the Hindu Kush and the Pamir which regulates the opposing directions of motion of the Indian and Eurasian plates. ?? 2022 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
101399
http://hdl.handle.net/10919/110455
https://doi.org/10.1016/j.gsf.2022.101399
13
4
Pamir-Hindu Kush
Seismicity
Stress field
Double-sided subduction
Low-velocity body
Double-sided subduction with contrasting polarities beneath the Pamir-Hindu Kush: Evidence from focal mechanism solutions and stress field inversion
oai:vtechworks.lib.vt.edu:10919/1141592023-11-29T19:06:54Zcom_10919_5540com_10919_24209com_10919_5553com_10919_111734com_10919_25796col_10919_71752col_10919_24267col_10919_111736
00925njm 22002777a 4500
dc
Kang, Junyao
author
Gill, Benjamin C.
author
Reid, Rachel E. B.
author
Zhang, Feifei
author
Xiao, Shuhai
author
2023-03-23
The early Neoproterozoic Era witnessed the initial ecological rise of eukaryotes at ca. 800 Ma. To assess whether nitrate availability played an important role in this evolutionary event, we measured nitrogen isotope compositions (δ<sup>15</sup>N) of marine carbonates from the early Tonian (ca. 1000 Ma to ca. 800 Ma) Huaibei Group in North China. The data reported here fill a critical gap in the δ<sup>15</sup>N record and indicate nitrate limitation in early Neoproterozoic oceans. A compilation of Proterozoic sedimentary δ<sup>15</sup>N data reveals a stepwise increase in δ<sup>15</sup>N values at ~800 Ma. Box model simulations indicate that this stepwise increase likely represents a ~50% increase in marine nitrate availability. Limited nitrate availability in early Neoproterozoic oceans may have delayed the ecological rise of eukaryotes until ~800 Ma when increased nitrate supply, together with other environmental and ecological factors, may have contributed to the transition from prokaryote-dominant to eukaryote-dominant marine ecosystems.
http://hdl.handle.net/10919/114159
https://doi.org/10.1126/sciadv.ade9647
9
Nitrate limitation in early Neoproterozoic oceans delayed the ecological rise of eukaryotes
oai:vtechworks.lib.vt.edu:10919/965152023-06-15T12:42:20Zcom_10919_5com_10919_25799com_10919_24227com_10919_5532com_10919_24209com_10919_5553com_10919_111086col_10919_70873col_10919_24302col_10919_24267col_10919_111087
00925njm 22002777a 4500
dc
Stamps, D. Sarah
author
Gallagher, James
author
Peckham, Scott
author
Sheehan, Anne
author
Potter, Nathan
author
Stoica, Maria
author
Njinju, Emmanuel A.
author
Fulker, David
author
Neumiller, Kodi
author
Easton, Zachary M.
author
White, Robin R.
author
Fuka, Daniel R.
author
2019-07-17
The Internet of Things (IoT), interconnection of computing devices embedded in everyday objects, has given geo-data scientists access to quickly growing numbers of devices for sensing; at costs no longer requiring hardware grants to access. The BALTO project has realized the importance of these growing sensor networks and has been working to integrate these sensors that can be combined into sustainable and synergistic research and education programs, from K-16 through senior researchers, centered on real-time monitoring and analytics of coupled ecosystems. BALTO takes advantage of the OpenSource Long-Range communication protocol (LoRa) to connect sensors to EarthCube Architectures.
http://hdl.handle.net/10919/96515
Fuka, Daniel [0000-0002-4468-2248]
Brokered Alignment of Long-Tailed Observations (BALTO) Applications in Geoscience
oai:vtechworks.lib.vt.edu:10919/970162020-10-22T03:26:33Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Cui, Huan
author
Xiao, Shuhai
author
Cai, Yaoping
author
Peek, Sara
author
Plummer, Rebecca E.
author
Kaufman, Alan J.
author
2019-11
The terminal Ediacaran Dengying Formation (c. 551.1-538.8 Ma) in South China is one of two successions where Ediacara-type macrofossils are preserved in carbonate facies along with skeletal fossils and bilaterian animal traces. Given the remarkable thickness of carbonate-bearing strata deposited in less than 12.3 million years, the Dengying Formation holds the potential for construction of a relatively continuous chemostratigraphic profile for the terminal Ediacaran Period. In this study, a detailed sedimentological and chemostratigraphic (delta 13C(carb), delta O-18(carb), delta C-13(org), delta S-34(pyrite), and Sr-87/Sr-86) investigation was conducted on the Dengying Formation at the Gaojiashan section, Ningqiang County of southern Shaanxi Province, South China. Sedimentological results reveal an overall shallow-marine depositional environment. Carbonate breccia, void-filling botryoidal precipitates and aragonite crystal fans are common in the Algal Dolomite Member of the Dengying Formation, suggesting that peritidal facies were repeatedly karstified. The timing of karstification was likely early, probably soon after the deposition of the dolomite sediments. The presence of authigenic aragonite cements suggests high alkalinity in the terminal Ediacaran ocean. Geochemical analysis of micro-drilled samples shows that distinct compositions are registered in different carbonate phases, which should be considered when constructing chemostratigraphic profiles representative of true temporal variations in seawater chemistry. Integrated chemostratigraphic data suggest enhanced burial of organic carbon and pyrite, and the occurrence of extensive marine anoxia (at least in the Gaojiashan Member). Rapid basinal subsidence and carbonate accumulation during a time of elevated seawater alkalinity and increased rates of pyrite burial may have facilitated the evolutionary innovation of early biomineralizing metazoans.
0016-7568
http://hdl.handle.net/10919/97016
https://doi.org/10.1017/S0016756819000293
156
11
31631899
1469-5081
geobiology
animal biomineralization
authigenesis
aragonite
karstification
alkalinity
Cloudina
Sedimentology and chemostratigraphy of the terminal Ediacaran Dengying Formation at the Gaojiashan section, South China
oai:vtechworks.lib.vt.edu:10919/1010602023-11-29T11:19:31Zcom_10919_98410com_10919_25796com_10919_24209com_10919_5553col_10919_98411col_10919_24267
00925njm 22002777a 4500
dc
Steffen, Rebekka
author
Steffen, Holger
author
Weiss, Robert
author
Lecavalier, Benoit S.
author
Milne, Glenn A.
author
Woodroffe, Sarah A.
author
Bennike, Ole
author
2020-09-15
Due to their large mass, ice sheets induce significant stresses in the Earth's crust. Stress release during deglaciation can trigger large-magnitude earthquakes, as indicated by surface faults in northern Europe. Although glacially-induced stresses have been analyzed in northern Europe, they have not yet been analyzed for Greenland. We know that the Greenland Ice Sheet experienced a large melting period in the early Holocene, and so here, we analyze glacially-induced stresses during deglaciation for Greenland for the first time. Instability occurs in southern Greenland, where we use a combined analysis of past sea level indicators and a model of glacially-induced fault reactivation to show that deglaciation of the Greenland Ice Sheet may have caused a large magnitude earthquake or a series of smaller magnitude earthquakes around 10,600 years ago offshore south-western Greenland. The earthquake(s) may have shifted relative sea level observations by several meters. If the earthquake-induced stress release was created during a single event, it could have produced a tsunami in the North Atlantic Ocean with runup heights of up to 7.2 m in the British Isles and up to 7.8 m along Canadian coasts. (C) 2020 The Authors. Published by Elsevier B.V.
0012-821X
116443
http://hdl.handle.net/10919/101060
https://doi.org/10.1016/j.epsl.2020.116443
546
1385-013X
glacial isostatic adjustment
relative sea-level data
tsunami
Greenland
glacially-triggered faulting
Early Holocene Greenland-ice mass loss likely triggered earthquakes and tsunami
oai:vtechworks.lib.vt.edu:10919/1065782021-11-11T08:11:37Zcom_10919_24226com_10919_5532com_10919_23842com_10919_5553com_10919_24209col_10919_24301col_10919_23843col_10919_24267
00925njm 22002777a 4500
dc
Allen, Kylie D.
author
Wegener, Gunter
author
Sublett, D. Matthew, Jr.
author
Bodnar, Robert J.
author
Feng, Xu
author
Wendt, Jenny
author
White, Robert H.
author
2021-10-27
Elemental carbon exists in different structural forms including graphite, diamond, fullerenes, and amorphous carbon. In nature, these materials are produced through abiotic chemical processes under high temperature and pressure but are considered generally inaccessible to biochemical synthesis or breakdown. Here, we identified and characterized elemental carbon isolated from consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB), which together carry out the anaerobic oxidation of methane (AOM). Two different AOM consortia, ANME-1a/HotSeep-1 and ANME-2a/c/Seep-SRB, produce a black material with similar characteristics to disordered graphite and amorphous carbon. Stable isotope probing studies revealed that the carbon is microbially generated during AOM. In addition, we found that select methanogens also produce amorphous carbon with similar characteristics to the carbon from AOM consortia. Biogenic amorphous carbon may serve as a conductive element to facilitate electron transfer, or redox active functional groups associated with the carbon could act as electron donors and acceptors.
http://hdl.handle.net/10919/106578
https://doi.org/10.1126/sciadv.abg9739
7
44
Biogenic formation of amorphous carbon by anaerobic methanotrophs and select methanogens
oai:vtechworks.lib.vt.edu:10919/1130192023-01-05T08:13:18Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Huang, Quancheng
author
Schmerr, Nicholas C.
author
King, Scott D.
author
Kim, Doyeon
author
Rivoldini, Attilio
author
Plesa, Ana-Catalina
author
Samuel, Henri
author
Maguire, Ross R.
author
Karakostas, Foivos
author
Lekić, Vedran
author
Charalambous, Constantinos
author
Collinet, Max
author
Myhill, Robert
author
Antonangeli, Daniele
author
Drilleau, Melanie
author
Bystricky, Misha
author
Bollinger, Caroline
author
Michaut, Chloe
author
Gudkova, Tamara
author
Irving, Jessica C. E.
author
Horleston, Anna
author
Fernando, Benjamin
author
Leng, Kuangdai
author
Nissen-Meyer, Tarje
author
Bejina, Frederic
author
Bozdag, Ebru
author
Beghein, Caroline
author
Waszek, Lauren
author
Siersch, Nicki C.
author
Scholz, John-Robert
author
Davis, Paul M.
author
Lognonné, Philippe
author
Pinot, Baptiste
author
Widmer-Schnidrig, Rudolf
author
Panning, Mark P.
author
Smrekar, Suzanne E.
author
Spohn, Tilman
author
Pike, William T.
author
Giardini, Domenico
author
Banerdt, W. Bruce
author
2022-10-18
Constraining the thermal and compositional state of the mantle is crucial for deciphering the formation and evolution of Mars. Mineral physics predicts that Mars’ deep mantle is demarcated by a seismic discontinuity arising from the pressure-induced phase transformation of the mineral olivine to its higher-pressure polymorphs, making the depth of this boundary sensitive to both mantle temperature and composition. Here, we report on the seismic detection of a midmantle discontinuity using the data collected by NASA’s InSight Mission to Mars that matches the expected depth and sharpness of the postolivine transition. In five teleseismic events, we observed triplicated P and S waves and constrained the depth of this discontinuity to be 1,006 ± 40 km by modeling the triplicated waveforms. From this depth range, we infer a mantle potential temperature of 1,605 ± 100 K, a result consistent with a crust that is 10 to 15 times more enriched in heat-producing elements than the underlying mantle. Our waveform fits to the data indicate a broad gradient across the boundary, implying that the Martian mantle is more enriched in iron compared to Earth. Through modeling of thermochemical evolution of Mars, we observe that only two out of the five proposed composition models are compatible with the observed boundary depth. Our geodynamic simulations suggest that the Martian mantle was relatively cold 4.5 Gyr ago (1,720 to 1,860 K) and are consistent with a present-day surface heat flow of 21 to 24 mW/m2
0027-8424
http://hdl.handle.net/10919/113019
https://doi.org/10.1073/pnas.2204474119
119
42
King, Scott [0000-0002-9564-5164]
36215469
1091-6490
interior of Mars
mantle transition zone
thermal evolution of Mars
Seismic detection of a deep mantle discontinuity within Mars by InSight
oai:vtechworks.lib.vt.edu:10919/1177392024-01-30T14:00:38Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Reid, Rachel E. B.
author
Crowley, Brooke Erin
author
Haupt, Ryan J.
author
2023-12
What can the stable isotope values of human and animal faeces tell us? This often under-appreciated waste product is gaining recognition across a variety of disciplines. Faecal isotopes provide a means of monitoring diet, resource partitioning, landscape use, tracking nutrient inputs and cycling, and reconstructing past climate and environment. Here, we review what faeces are composed of, their temporal resolution, and how these factors may be impacted by digestive physiology and efficiency. As faeces are often used to explore diet, we clarify how isotopic offsets between diet and faeces can be calculated, as well as some differences among commonly used calculations that can lead to confusion. Generally, faecal carbon isotope (δ13C) values are lower than those of the diet, while faecal nitrogen isotope values (δ15N) values are higher than in the diet. However, there is considerable variability both within and among species. We explore the role of study design and how limitations stemming from a variety of factors can affect both the reliability and interpretability of faecal isotope data sets. Finally, we summarise the various ways in which faecal isotopes have been applied to date and provide some suggestions for future research. Despite remaining challenges, faecal isotope data are poised to continue to contribute meaningfully to a variety of fields.
1464-7931
https://hdl.handle.net/10919/117739
https://doi.org/10.1111/brv.12996
98
6
Reid, Rachel [0000-0002-2091-0701]
37438959
1469-185X
carbon
nitrogen
digestion
discrimination
turnover
The prospects of poop: a review of past achievements and future possibilities in faecal isotope analysis
oai:vtechworks.lib.vt.edu:10919/1105992022-06-11T07:12:27Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Mitchell, Emily G.
author
Evans, Scott D.
author
Chen, Zhe
author
Xiao, Shuhai
author
2022-05-19
Trace fossils record foraging behaviors, the search for resources in patchy environments, of animals in the rock record. Quantification of the strength, density, and nature of foraging behaviors enables the investigation of how these may have changed through time. Here, we present a novel approach to explore such patterns using spatial point process analyses to quantify the scale and strength of ichnofossil spatial distributions on horizontal bedding planes. To demonstrate the utility of this approach, we use two samples from the terminal Ediacaran Shibantan Member in South China (between 551 and 543 Ma) and the early Cambrian Nagaur Sandstone in northwestern India (between 539 and 509 Ma). We find that ichnotaxa on both surfaces exhibited significant nonhomogeneous lateral patterns, with distinct levels of heterogeneity exhibited by different types of trace fossils. In the Shibantan, two ichnotaxa show evidence for mutual positive aggregation over a shared resource, suggesting the ability to focus on optimal resource areas. Trace fossils from the Nagaur Sandstone exhibit more sophisticated foraging behavior, with greater niche differentiation. Critically, mark correlation functions highlight significant spatial autocorrelation of trace fossil orientations, demonstrating the greater ability of these Cambrian tracemakers to focus on optimal patches. Despite potential limitations, these analyses hint at changes in the development and optimization of foraging at the Ediacaran/Cambrian transition and highlight the potential of spatial point process analysis to tease apart subtle differences in behavior in the trace fossil record.
0094-8373
PII S0094837322000161
http://hdl.handle.net/10919/110599
https://doi.org/10.1017/pab.2022.16
1938-5331
flight search patterns
Yangtze gorges area
microbial mats
levy flight
foraging patterns
heritage site
fossil
heterogeneity
information
insights
A new approach for investigating spatial relationships of ichnofossils: a case study of Ediacaran-Cambrian animal traces
oai:vtechworks.lib.vt.edu:10919/874262023-04-18T18:48:37Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553com_10919_23765com_10919_24369com_10919_5539col_10919_70873col_10919_24267col_10919_24353col_10919_24370
00925njm 22002777a 4500
dc
Serra-Maia, Rui
author
Winkler, Christopher
author
Murayama, Mitsuhiro
author
Tranhuu, Kevin
author
Michel, F. Marc
author
2018-06-18
Oxygen at the surface of nanosized platinum has a direct effect on catalytic activity of oxidation−reduction chemical reactions. However, the abundance and speciation of oxygen remain uncertain for platinum with different particle size and shape characteristics, which has hindered the development of fundamental property−activity relationships. We have characterized two commercially available platinum nanocatalysts known as Pt black and Pt nanopowder to evaluate the effects of synthesis and heating conditions on the physical and surface chemical properties, as well as on catalytic activity. Characterization using complementary electron microscopy, X-ray scattering, and spectroscopic methods showed that the larger average crystallite size of Pt nanopowder (23 nm) compared to Pt black (11 nm) corresponds with a 70% greater surface oxygen concentration. Heating the samples in air resulted in an increase in surface oxygen concentration for both nanocatalysts. Surface oxygen associated with platinum is in the form of chemisorbed oxygen, and no significant amounts of chemically bonded platinum oxide were found for any of the samples. The increase in surface oxygen abundance during heating depends on the initial size and surface oxygen content. Hydrogen peroxide decomposition rate measurements showed that larger particle size and higher surface chemisorbed oxygen correlate with enhanced catalytic activity. These results are particularly important for future studies that aim to relate the properties of platinum, or other metal nanocatalysts, with surface reactivity.
2574-0962
http://hdl.handle.net/10919/87426
https://doi.org/10.1021/acsaem.8b00474
1
Michel, Frederick [0000-0003-2817-980X]
2574-0962
Abundance and Speciation of Surface Oxygen on Nanosized Platinum Catalysts and Effect on Catalytic Activity
oai:vtechworks.lib.vt.edu:10919/803522020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Baziotis, Ioannis P.
author
Liu, Yang
author
DeCarli, Paul S.
author
Melosh, H. Jay
author
McSween, Harry Y.
author
Bodnar, Robert J.
author
Taylor, Lawrence A.
author
2013-01-29
High-pressure minerals in meteorites provide clues for the impact processes that excavated, launched and delivered these samples to Earth. Most Martian meteorites are suggested to have been excavated from 3 to 7 km diameter impact craters. Here we show that the Tissint meteorite, a 2011 meteorite fall, contains virtually all the high-pressure phases (seven minerals and two mineral glasses) that have been reported in isolated occurrences in other Martian meteorites. Particularly, one ringwoodite (75 140 𝜇m²) represents the largest grain observed in all Martian samples. Collectively, the ubiquitous high-pressure minerals of unusually large sizes in Tissint indicate that shock metamorphism was widely dispersed in this sample (B25 GPa and B2,000 1C). Using the size and growth kinetics of the ringwoodite grains, we infer an initial impact crater with B90 km diameter, with a factor of 2 uncertainty. These energetic conditions imply alteration of any possible low-T minerals in Tissint.
http://hdl.handle.net/10919/80352
https://doi.org/10.1038/ncomms2414
4
The Tissint Martian meteorite as evidence for the largest impact excavation
oai:vtechworks.lib.vt.edu:10919/819482023-04-18T18:48:28Zcom_10919_5com_10919_25799com_10919_19035com_10919_5539com_10919_24209com_10919_5553col_10919_70873col_10919_24290col_10919_24267
00925njm 22002777a 4500
dc
Meyer, Mike
author
Polys, Nicholas F.
author
Yaqoob, Humza
author
Hinnov, Linda
author
Xiao, Shuhai
author
2017-09
Trace fossils are superb lines of evidence for examining the ancient biologic world because they offer an opportunity to infer behavioral ecology of organisms. However, traces can be difficult to parse from their matrix, which leads to the loss of important morphological and behavioral data. This is especially true for the earliest marine animal traces from the Ediacaran Period (635–541 Ma), which are usually small (<5 mm in diameter) and simple (mostly small horizontal trails and burrows), and are sometimes difficult to be distinguished from co-existing tubular body fossils. There is also evidence that the prevalence of microbial substrates in Ediacaran oceans may have influenced emerging trace makers in nonactualistic ways from a late Phanerozoic perspective (e.g., microbial mats may have facilitated a strong geochemical gradient across the sediment-water interface). Therefore, the discovery of the relatively large traces of Lamonte trevallis from the Ediacaran Shibantan Member of the Denying Formation (~551–541 Ma) in the Yangtze Gorges area of South China provides a unique opportunity to study early bioturbators. These trace fossils are large enough and have sufficient compositional contrast (relative to the matrix) for in situ analysis via X-ray computed tomography (CT) and microcomputed tomography (microCT). Each analytical method has its own advantages and disadvantages. CT scans can image larger specimens, but cannot adequately resolve small features of interest. MicroC scans can achieve higher resolution, but can only be used with small samples and may involve more post-processing than CT scans. As demonstrated in this study, X-ray CT and microCT in combination with other 3D imaging techniques and resources have the potential to resolve the 3D morphology of Ediacaran trace fossils. A new Volumetric Bioturbation Intensity (VBI) is also proposed, which quantifies whole rock bioturbation using 3D analysis of subsurface traces. Combined with the ability to examine trace fossils in situ, the VBI can enhance our view of ancient ecologies and life’s enduring relationship with sediments.
0301-9268
http://hdl.handle.net/10919/81948
https://doi.org/10.1016/j.precamres.2017.05.010
298
Xiao, S [0000-0003-4655-2663]
Beyond the stony veil: Reconstructing the Earth’s earliest large animal traces via computed tomography X-ray imaging
oai:vtechworks.lib.vt.edu:10919/1018862024-03-14T15:43:37Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Carlson, J. Kade
author
Bemis, Sean P.
author
Toke, Nathan
author
Bishop, Bradley
author
Taylor, T. Patrick
author
2018-02-01
The Denali fault in south-central Alaska is a major right-lateral strike-slip fault that parallels the Alaska Range for much of its length and represents the largest seismogenic source for interior Alaska. The fault system is over 1200 km in length, and identification of paleoseismic sites that preserve more than 2–3 paleoearthquakes has proven challenging due to its remote location and difficulty of access. In 2012 and 2015, we developed the Dead Mouse site, which provides the first long paleoearthquake record west of the 2002 Mw 7.9 Denali fault earthquake sequence rupture extent. This site is located on the west-central segment of the Denali fault near the southernmost intersection of the Parks Highway and the Nenana River. We hand-excavated three fault-perpendicular trenches and documented new evidence for seven surface-rupturing paleoearthquakes from deformation in the upper 2.5 m of stratigraphy. Evidence for these events includes offset units, filled fissures, upward fault terminations, and an angular unconformity. Chronological constraints from Bayesian sequence modeling of radiocarbon ages and one tentative tephra correlation indicate these seven earthquakes occurred at 388 cal B.P. (442–319; E1), 807 cal B.P. (853–764; E2), 1282 cal B.P. (1392–1160; E3), 2652 cal B.P. (2805–2460; E4), 3402 cal B.P. (3790–3010; E5*), 5673 cal B.P. (6676–4632; E6*), and 6987 cal B.P. (7281–6668; E7*). Although there are likely missing earthquakes in our chronology prior to E4, the intervals between E1 and E4 suggest significant variability in recurrence period at the Dead Mouse site. Additional paleoearthquake chronologies at neighboring sites are required to make reliable estimates of the spatial and temporal rupture history for the west-central Denali fault, but our data demonstrate the potential for recurrence periods as short as 300–600 yrs, well within range of the current open interval for the Denali fault at the Nenana River.
0037-1106
http://hdl.handle.net/10919/101886
https://doi.org/10.1785/0120170070
108
1
Bemis, Sean [0000-0001-7854-6394]
1943-3573
LATE PLEISTOCENE
SLIP DISTRIBUTION
SURFACE RUPTURE
CHRONOLOGIES
RANGE
TECTONICS
EVOLUTION
Documentation of Seven Earthquakes over the Past similar to 7000 Years on the West-Central Denali Fault at the Nenana River, Alaska
oai:vtechworks.lib.vt.edu:10919/803562020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Schiffbauer, James D.
author
Xiao, Shuhai
author
Cai, Yaoping
author
Wallace, Adam F.
author
Hua, Hong
author
Hunter, Jerry
author
Xu, Huifang
author
Peng, Yongbo
author
Kaufman, Alan J.
author
2014-12-17
Soft-tissue fossils capture exquisite biological detail and provide our clearest views onto the rise of animals across the Ediacaran–Cambrian transition. The processes contributing to fossilization of soft tissues, however, have long been a subject of debate. The Ediacaran Gaojiashan biota displays soft-tissue preservational styles ranging from pervasive pyritization to carbonaceous compression, and thus provides an excellent opportunity to dissect the relationships between these taphonomic pathways. Here geochemical analyses of the Gaojiashan fossil Conotubus hemiannulatus show that pyrite precipitation was fuelled by the degradation of labile tissues through bacterial sulfate reduction (BSR). Pyritization initiated with nucleation on recalcitrant tube walls, proceeded centripetally, decelerated with exhaustion of labile tissues and possibly continued beneath the BSR zone. We propose that pyritization and kerogenization are regulated principally by placement and duration of the decaying organism in different microbial zones of the sediment column, which hinge on post-burial sedimentation rate and/or microbial zone thickness.
http://hdl.handle.net/10919/80356
https://doi.org/10.1038/ncomms6754
5
A unifying model for Neoproterozoic–Palaeozoic exceptional fossil preservation through pyritization and carbonaceous compression
oai:vtechworks.lib.vt.edu:10919/1010562021-12-16T15:22:17Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Laubach, S. E.
author
Lander, R. H.
author
Criscenti, L. J.
author
Anovitz, L. M.
author
Urai, J. L.
author
Pollyea, Ryan M.
author
Hooker, J. N.
author
Narr, W.
author
Evans, M. A.
author
Kerisit, S. N.
author
Olson, J. E.
author
Dewers, T.
author
Fisher, D.
author
Bodnar, Robert J.
author
Evans, B.
author
Dove, Patricia M.
author
Bonnell, L. M.
author
Marder, M. P.
author
Pyrak-Nolte, L.
author
2019-09-13
Fracture pattern development has been a challenging area of research in the Earth sciences for more than 100 years. Much has been learned about the spatial and temporal complexity inherent to these systems, but severe challenges remain. Future advances will require new approaches. Chemical processes play a larger role in opening‐mode fracture pattern development than has hitherto been appreciated. This review examines relationships between mechanical and geochemical processes that influence the fracture patterns recorded in natural settings. For fractures formed in diagenetic settings (~50 to 200 °C), we review evidence of chemical reactions in fractures and show how a chemical perspective helps solve problems in fracture analysis. We also outline impediments to subsurface pattern measurement and interpretation, assess implications of discoveries in fracture history reconstruction for process‐based models, review models of fracture cementation and chemically assisted fracture growth, and discuss promising paths for future work. To accurately predict the mechanical and fluid flow properties of fracture systems, a processes‐based approach is needed. Progress is possible using observational, experimental, and modeling approaches that view fracture patterns and properties as the result of coupled mechanical and chemical processes. A critical area is reconstructing patterns through time. Such data sets are essential for developing and testing predictive models. Other topics that need work include models of crystal growth and dissolution rates under geological conditions, cement mechanical effects, and subcritical crack propagation. Advances in machine learning and 3‐D imaging present opportunities for a mechanistic understanding of fracture formation and development, enabling prediction of spatial and temporal complexity over geologic timescales. Geophysical research with a chemical perspective is needed to correctly identify and interpret fractures from geophysical measurements during site characterization and monitoring of subsurface engineering activities.
http://hdl.handle.net/10919/101056
https://doi.org/10.1029/2019RG000671
57
The Role of Chemistry in Fracture Pattern Development and Opportunities to Advance Interpretations of Geological Materials
oai:vtechworks.lib.vt.edu:10919/1177332024-01-30T09:36:59Zcom_10919_5com_10919_25799com_10919_18738com_10919_5539com_10919_24209com_10919_5553com_10919_24211col_10919_70873col_10919_23145col_10919_24267col_10919_24287
00925njm 22002777a 4500
dc
Wu, Shuang
author
Smith, David A.
author
Nakarmi, Prabandha
author
Rai, Anish
author
Clavel, Michael
author
Hudait, Mantu K.
author
Zhao, Jing
author
Michel, F. Marc
author
Mewes, Claudia
author
Mewes, Tim
author
Emori, Satoru
author
2021-09-08
We examine room-temperature magnetic relaxation in polycrystalline Fe films. Out-of-plane ferromagnetic resonance (FMR) measurements reveal Gilbert damping parameters of $\approx$ 0.0024 for Fe films with thicknesses of 4-25 nm, regardless of their microstructural properties. The remarkable invariance with film microstructure strongly suggests that intrinsic Gilbert damping in polycrystalline metals at room temperature is a local property of nanoscale crystal grains, with limited impact from grain boundaries and film roughness. By contrast, the in-plane FMR linewidths of the Fe films exhibit distinct nonlinear frequency dependences, indicating the presence of strong extrinsic damping. To fit our in-plane FMR data, we have used a grain-to-grain two-magnon scattering model with two types of correlation functions aimed at describing the spatial distribution of inhomogeneities in the film. However, neither of the two correlation functions is able to reproduce the experimental data quantitatively with physically reasonable parameters. Our findings advance the fundamental understanding of intrinsic Gilbert damping in structurally disordered films, while demonstrating the need for a deeper examination of how microstructural disorder governs extrinsic damping.
https://hdl.handle.net/10919/117733
Michel, Frederick [0000-0003-2817-980X]
Hudait, Mantu [0000-0002-9789-3081]
cond-mat.mtrl-sci
cond-mat.mes-hall
Room-Temperature Intrinsic and Extrinsic Damping in Polycrystalline Fe Thin Films
oai:vtechworks.lib.vt.edu:10919/868202023-04-18T18:49:02Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Xiao, Shuhai
author
Tang, Qing
author
2018-06-29
2397-8554
http://hdl.handle.net/10919/86820
https://doi.org/10.1042/ETLS20170165
2
Xiao, Shuhai [0000-0003-4655-2663]
2397-8562
After the boring billion and before the freezing millions: evolutionary patterns and innovations in the Tonian Period
oai:vtechworks.lib.vt.edu:10919/1030232023-04-28T19:01:47Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
King, Scott D.
author
2019-08-01
http://hdl.handle.net/10919/103023
King, Scott [0000-0002-9564-5164]
Mathematics of the not-so-solid solid Earth
oai:vtechworks.lib.vt.edu:10919/914712020-10-22T05:00:53Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Pollyea, Ryan M.
author
Chapman, Martin C.
author
Jayne, Richard S.
author
Wu, Hao
author
2019
Oilfield wastewater disposal causes fluid pressure transients that induce earthquakes. Here we show that, in addition to pressure transients related to pumping, there are pressure transients caused by density differences between the wastewater and host rock fluids. In northern Oklahoma, this effect caused earthquakes to migrate downward at ~0.5 km per year during a period of high-rate injections. Following substantial injection rate reductions, the downward earthquake migration rate slowed to ~0.1 km per year. Our model of this scenario shows that the density-driven pressure front migrates downward at comparable rates. This effect may locally increase fluid pressure below injection wells for 10+ years after substantial injection rate reductions. We also show that in north-central Oklahoma the relative proportion of high-magnitude earthquakes increases at 8+ km depth. Thus, our study implies that, following injection rate reductions, the frequency of high-magnitude earthquakes may decay more slowly than the overall earthquake rate.
http://hdl.handle.net/10919/91471
https://doi.org/10.1038/s41467-019-11029-8
10
High density oilfield wastewater disposal causes deeper, stronger, and more persistent earthquakes
oai:vtechworks.lib.vt.edu:10919/1179722024-03-15T14:38:28Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Shields, Graham A.
author
Strachan, Robin A.
author
Porter, Susannah M.
author
Halverson, Galen P.
author
Macdonald, Francis A.
author
Plumb, Kenneth A.
author
de Alvarenga, Carlos J.
author
Banerjee, Dhiraj M.
author
Bekker, Andrey
author
Bleeker, Wouter
author
Brasier, Alexander
author
Chakraborty, Partha P.
author
Collins, Alan S.
author
Condie, Kent
author
Das, Kaushik
author
Evans, David AD D.
author
Ernst, Richard
author
Fallick, Anthony E.
author
Frimmel, Hartwig
author
Fuck, Reinhardt
author
Hoffman, Paul F.
author
Kamber, Balz S.
author
Kuznetsov, Anton B.
author
Mitchell, Ross N.
author
Poire, Daniel G.
author
Poulton, Simon W.
author
Riding, Robert
author
Sharma, Mukund
author
Storey, Craig
author
Stueeken, Eva
author
Tostevin, Rosalie
author
Turner, Elizabeth
author
Xiao, Shuhai
author
Zhang, Shuanhong
author
Zhou, Ying
author
Zhu, Maoyan
author
2021-07-07
The geological timescale before 720 Ma uses rounded absolute ages rather than specific events recorded in rocks to subdivide time. This has led increasingly to mismatches between subdivisions and the features for which they were named. Here we review the formal processes that led to the current timescale, outline rock-based concepts that could be used to subdivide pre-Cryogenian time and propose revisions. An appraisal of the Precambrian rock record confirms that purely chronostratigraphic subdivision would require only modest deviation from current chronometric boundaries, removal of which could be expedited by establishing event-based concepts and provisional, approximate ages for eon-, era-and period-level subdivisions. Our review leads to the following conclusions: (1) the current informal four-fold Archean subdivision should be simplified to a tripartite scheme, pending more detailed analysis, and (2) an improved rock-based Proterozoic Eon might comprise a Paleoproterozoic Era with three periods (early Paleoproterozoic or Skourian, Rhyacian, Orosirian), Mesoproterozoic Era with four periods (Statherian, Calymmian, Ectasian, Stenian) and a Neoproterozoic Era with four periods ( pre-Tonian or Kleisian, Tonian, Cryogenian and Ediacaran). These proposals stem from a wide community and could be used to guide future development of the pre-Cryogenian timescale by international bodies.
0016-7649
https://hdl.handle.net/10919/117972
https://doi.org/10.1144/jgs2020-222
179
1
Xiao, Shuhai [0000-0003-4655-2663]
2041-479X
Geology
ORGANIC-WALLED MICROFOSSILS
VASE-SHAPED MICROFOSSILS
LARGE IGNEOUS PROVINCES
PRECAMBRIAN TIME-SCALE
DETRITAL ZIRCON GEOCHRONOLOGY
SNOWBALL EARTH HYPOTHESIS
CARBON-ISOTOPE EXCURSION
NORTH CHINA CRATON
U-PB
PILBARA CRATON
A template for an improved rock-based subdivision of the pre-Cryogenian timescale
oai:vtechworks.lib.vt.edu:10919/253052020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Norabuena, E. O.
author
Snoke, J. A.
author
James, D. E.
author
1994-05
Arrival times from intermediate-depth (110-150 km) earthquakes within the region of flat subduction beneath the subandean zone and foreland basins of east-central Peru provide constraints on the geometry and velocity structure of the subducting Nazca plate. Hypocentral locations and origin times for these events were determined using observations from a 15 station digitally recording locator array deployed in the epicentral region of eastern Peru. Observed P wave arrival times for coastal stations in Peru, some 3-6-degrees from the epicenters, are up to 4 s early relative to predicted arrival times based on the best fit velocity-depth model used for hypocenter locations. These large negative time residuals appear to be the result of propagation paths which have long segments in the colder, higher-velocity subducting plate. P wave travel times were modeled for the effects of the slab using three-dimensional (3-D) ray tracing. Computed ray paths show that travel times to coastal stations for the eastern Peru events can be satisfactorily modeled with average velocities relative to the surrounding mantle 6% lower within the uppermost slab (assumed on the basis of other studies to be unconverted basaltic oceanic crust 6 km thick) and 8% higher within the cold uppermost mantle of the slab. Ray tracing for this plate model shows that P wave ''shadow zones'' can occur if the source-slab-receiver geometry results in seismic rays passing through regions in which the clip angle of the slab changes significantly. Such geometries exist for seismic waves propagating to some coastal stations from intermediate-depth earthquakes located east of the Andes. Observed first-arrival times for such cases do in fact have smaller negative residuals than those for geometries which allow for ''direct'' paths at similar distances. Modeling such arrivals as internally reflected waves propagating through the high-velocity part of the plate produces a significant improvement in the travel time residuals. For the slab velocities given above, we obtain a model thickness of approximately 36 km for the cold slab interior and a slight northwest component of dip in the region of subhorizontal subduction.
Norabuena, E. O., J. A. Snoke, and D. E. James (1994), Structure of the subducting Nazca Plate beneath Peru, J. Geophys. Res., 99(B5), 9215-9226, doi:10.1029/94JB00126.
0148-0227
http://hdl.handle.net/10919/25305
http://onlinelibrary.wiley.com/doi/10.1029/94JB00126/pdf
https://doi.org/10.1029/94jb00126
slab mantle interface
spatial-distribution
south-america
seismicity
earthquakes
lithosphere
traveltimes
tectonics
waves
zone
Structure of the subducting Nazca plate beneath Peru
oai:vtechworks.lib.vt.edu:10919/990462022-02-26T22:22:44Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Caraballo, Manuel A.
author
Wanty, Richard B.
author
Verplanck, Philip L.
author
Navarro-Valdivia, Leonardo
author
Ayora, Carlos
author
Hochella, Michael F. Jr.
author
2019-08-05
Aluminum precipitates control the hydrochemistry and mineralogy of a broad variety of environments on Earth (e.g., acid mine drainage, AMD, coastal wetlands, boreal and alpine streams, tropical acid sulfate soils, laterites and bauxites, ...). However, the geochemical and mineralogical processes controlling Al (and other associated metals and metalloids) transport and removal in those environments are not fully understood. The geochemical system of Paradise Portal (Colorado, USA) comprises sulfate-rich mildly acidic waters, the hydrochemistry of which is directly controlled by the massive precipitation of hydrobasaluminite Al-4(SO4)(OH)(10)center dot 12-36H(2)O. Three connected but discernible aluminum precipitation stages were identified and described: 1) nanoparticle formation and size decrease along the creek, 2) hydrobasaluminite neoformation on the riverbed, and 3) precipitate accretion and accumulation on the riverbed leading to Al and Fe banded formations. The co-occurrence of Al and Si in the system was observed, recording significant amounts of Si accompanying the three different components of the system (i.e., nanoparticles and fresh and aged Al-precipitates). Also, abrupt and minor changes in the sedimentary record were described and proposed to be the response of the system to seasonal and interannual changes in AMD chemistry. Concerning the mobility of other metals and metalloids, P, Th, V, W, Ti and B showed a tendency to be preferentially incorporated into hydrobasaluminite, while others like Be, As, Se or Ba tend to remain dissolved in the water.
0009-2541
http://hdl.handle.net/10919/99046
https://doi.org/10.1016/j.chemgeo.2019.04.013
519
1872-6836
Hydrobasaluminite nanoparticles
Aluminum and metals mobility
Acid rock drainage
Nanomineral
Banded aluminum and iron formations
Aluminum mobility in mildly acidic mine drainage: Interactions between hydrobasaluminite, silica and trace metals from the nano to the meso-scale
oai:vtechworks.lib.vt.edu:10919/1097812022-05-03T07:12:03Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Hall, S. M.
author
Beard, J. S.
author
Potter, C. J.
author
Bodnar, Robert J.
author
Neymark, L. A.
author
Paces, J. B.
author
Johnson, C. A.
author
Breit, G. N.
author
Zielinksi, R. A.
author
Aylor, G. J.
author
2022-03
The Coles Hill uranium deposit, with an indicated resource of about 130 Mlb of U3O8, is the largest unmined uranium deposit in the United States. The deposit is hosted in the Taconian (approx. 480-450 Ma) Martinsville igneous complex, which consists of the Ordovician Leatherwood Granite (granodiorite) and the Silurian Rich Acres Formation (diorite). The host rock was metamorphosed to orthogneiss during the Alleghanian orogeny (approx. 325-260 Ma), when it also underwent dextral strike-slip movement along the Brookneal shear zone. During the Triassic, extensional tectonics led to the development of the Dan River Basin that lies east of Coles Hill. The mineralized zone is hosted in brittle structures in the footwall of the Triassic Chatham fault that forms the western edge of the basin. Within brittle fracture zones, uranium silicate and uranium-bearing fluorapatite with traces of brannerite form veins and breccia-fill with chlorite, quartz, titanium oxide, pyrite, and calcite. Uranium silicates also coat and replace primary titanite, zircon, ilmenite, and sulfides. Sodium metasomatism preceded and accompanied uranium mineralization, pervasively altering host rock and forming albite from primary feldspar, depositing limpid albite rims on igneous feldspar, altering titanite to titanium oxide and calcite, and forming riebeckite. Various geothermometers indicate temperatures of less than similar to 200 degrees C during mineralization. In situ U-Pb analyses of titanite, Ti-oxide, and apatite, along with Rb/Sr and U/Pb isotope systematics of whole-rock samples, resolve the timing of geologic processes affecting Coles Hill. The host Leatherwood Granite containing primary euhedral titanite is dated at 450 to 445 Ma, in agreement with previously obtained ages from zircon in the Martinsville igneous complex. A regional metamorphic event at 330 to 310 Ma formed anhedral titanite and some apatite, reequilibrated whole-rock Rb/Sr and U-Pb isotopes, and is interpreted to have coincided with movement along the Brookneal shear zone. During shearing and metamorphism, primary refractory uranium-bearing minerals including titanite, zircon, and uranothorite were recrystallized, and uranium was liberated and mixed locally with hematite, clay, and other fine-grained minerals. Uranium mineralization was accompanied by a metasomatic episode between 250 and 200 Ma that reset the Rb-Sr and U-Pb isotope systems and formed titanium oxide and apatite that are associated and, in places, intimately intergrown with uranium silicate dating mineralization. This event coincides with rifting that formed the Dan River Basin and was a precursor to the breakup of Pangea. The orientation of late-stage tectonic stylolites is compatible with their formation during Late Triassic to Early Jurassic basin inversion, postdating the main stage of uranium mineralization and effectively dating mineralization as Mesozoic. Based on the close spatial and temporal association of uranium with apatite, we propose that uranium was carried as a uranyl-phosphate complex. Uranium was locally reduced by coupled redox reactions with ferrous iron and sulfide minerals in the host rock, forming uranium silicates. The release of calcium during sodium metasomatic alteration of primary calcic feldspar and titanite in the host rock initiated successive reactions in which uranium and phosphate in mineralizing fluids combined with calcium to form U-enriched fluorapatite. Based on the deposit mineralogy, oxygen isotope geochemistry, and trace element characteristics of uranium silicate and gangue minerals, the primary mineralizing fluids likely included connate and/or meteoric water sourced from the adjacent Dan River Basin. High heat flow related to Mesozoic rifting may have driven these (P-Na-F- rich) fluids through local aquifers and into basin margin faults, transporting uranium from the basin or mobilizing uranium from previously formed U minerals in the Brookneal shear zone, or from U-enriched older basement rock.
0361-0128
http://hdl.handle.net/10919/109781
https://doi.org/10.5382/econgeo.4874
117
2
1554-0774
Central Appalachian Piedmont
U-Pb Geochronology
Na-Metasomatism
Zircon
Ordovician
Brookneal
Uraninite
Shrimp
Basin
Stratigraphy
The Coles Hill Uranium Deposit, Virginia, USA: Geology, Geochemistry, Geochronology, and Genetic Model
oai:vtechworks.lib.vt.edu:10919/1180992024-03-15T15:17:30Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Gomez, Demian D.
author
Bevis, Michael G.
author
Smalley, Robert
author
Durand, Michael
author
Willis, Michael J.
author
Caccamise, Dana J.
author
Kendrick, Eric
author
Skvarca, Pedro
author
Sobrero, Franco S.
author
Parra, Hector
author
Casassa, Gino
author
2022-06-10
The Patagonia Icefields (PIF) are the largest non-polar ice mass in the southern hemisphere. The icefields cover an area of approximately 16,500 km2 and are divided into the northern and southern icefields, which are ~ 4000 km2 and ~ 12,500 km2, respectively. While both icefields have been losing mass rapidly, their responsiveness to various climate drivers, such as the El Niño-Southern Oscillation, is not well understood. Using the elastic response of the earth to loading changes and continuous GPS data we separated and estimated ice mass changes observed during the strong El Niño that started in 2015 from the complex hydrological interactions occurring around the PIF. During this single event, our mass balance estimates show that the northern icefield lost ~ 28 Gt of mass while the southern icefield lost ~ 12 Gt. This is the largest ice loss event in the PIF observed to date using geodetic data.
2045-2322
10.1038/s41598-022-13252-8 (PII)
https://hdl.handle.net/10919/118099
https://doi.org/10.1038/s41598-022-13252-8
12
1
35688878
2045-2322
Reference Frames
Mass-Balance
Glacier
Transient ice loss in the Patagonia Icefields during the 2015-2016 El Nino event
oai:vtechworks.lib.vt.edu:10919/1130362023-01-05T08:13:31Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Owens, Jeremy D.
author
Gill, Benjamin C.
author
Jenkyns, Hugh C.
author
Bates, Steven M.
author
Severmann, Silke
author
Kuypers, Marcel M. M.
author
Woodfine, Richard G.
author
Lyons, Timothy W.
author
2013
The Mesozoic Era is characterized by numerous oceanic anoxic events (OAEs) that are diagnostically expressed by widespread marine organic-carbon burial and coeval carbon-isotope excursions. Here we present coupled high-resolution carbon- and sulfurisotope data from four European OAE 2 sections spanning the Cenomanian-Turonian boundary that show roughly parallel positive excursions. Significantly, however, the interval of peak magnitude for carbon isotopes precedes that of sulfur isotopes with an estimated offset of a few hundred thousand years. Based on geochemical box modeling of organic-carbon and pyrite burial, the sulfur-isotope excursion can be generated by transiently increasing the marine burial rate of pyrite precipitated under euxinic (i.e., anoxic and sulfidic) water-column conditions. To replicate the observed isotopic offset, the model requires that enhanced levels of organic-carbon and pyrite burial continued a few hundred thousand years after peak organic-carbon burial, but that their isotope records responded differently due to dramatically different residence times for dissolved inorganic carbon and sulfate in seawater. The significant inference is that euxinia persisted post-OAE, but with its global extent dwindling over this time period. The model further suggests that only ∼5% of the global seafloor area was overlain by euxinic bottom waters during OAE 2. Although this figure is ∼30x greater than the small euxinic fraction present today (∼0.15%), the result challenges previous suggestions that one of the best-documented OAEs was defined by globally pervasive euxinic deep waters. Our results place important controls instead on local conditions and point to the difficulty in sustaining whole-ocean euxinia.
0027-8424
1305304110 (PII)
http://hdl.handle.net/10919/113036
https://doi.org/10.1073/pnas.1305304110
110
46
Gill, Benjamin [0000-0001-7402-0811]
24170863
1091-6490
carbonate-associated sulfur
geochemical modeling
ORBITAL TIME-SCALE
SEAWATER CHEMISTRY
CARBON
SULFATE
SEA
PHOSPHORUS
REDOX
FLUCTUATIONS
STRATIGRAPHY
TEMPERATURES
14 Life Below Water
Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2
oai:vtechworks.lib.vt.edu:10919/743072023-06-13T17:50:55Zcom_10919_5com_10919_25799com_10919_24227com_10919_5532com_10919_24209com_10919_5553col_10919_70873col_10919_24302col_10919_24267
00925njm 22002777a 4500
dc
Zhang, H.
author
Xiao, S.
author
Liu, Y.
author
Yuan, X.
author
Wan, B.
author
Muscente, A. D.
author
Shao, T.
author
Gong, H.
author
Cao, G.
author
2015-11-26
Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated cuticular plates, longitudinal muscles, dorsoventral muscles, and ganglia. Molecular clock estimates suggest that kinorhynchs may have diverged in the Ediacaran Period. Remarkably, no kinorhynch fossils have been discovered, in sharp contrast to priapulids and loriciferans that are represented by numerous Cambrian fossils. Here we describe several early Cambrian (~535 million years old) kinorhynch-like fossils, including the new species Eokinorhynchus rarus and two unnamed but related forms. E. rarus has characteristic scalidophoran features, including an introvert with pentaradially arranged hollow scalids. Its trunk bears at least 20 annuli each consisting of numerous small rectangular plates, and is armored with five pairs of large and bilaterally placed sclerites. Its trunk annuli are reminiscent of the epidermis segments of kinorhynchs. A phylogenetic analysis resolves E. rarus as a stem-group kinorhynch. Thus, the fossil record confirms that all three scalidophoran phyla diverged no later than the Cambrian Period.
http://hdl.handle.net/10919/74307
https://doi.org/10.1038/srep16521
5
2045-2322
Animals
Extinction, Biological
Fossils
Ganglia
Genetic Speciation
Muscles
Nematoda
Phylogeny
Armored kinorhynch-like scalidophoran animals from the early Cambrian.
oai:vtechworks.lib.vt.edu:10919/1180902024-03-18T11:05:53Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Perkins, Jonathan P.
author
Finnegan, Noah J.
author
de Silva, Shanaka L.
author
Willis, Michael J.
author
2019-11-08
Wind abrasion is important for planetary landscape evolution, and wind-abraded bedrock landscapes contain many landforms that are difficult to interpret. Here we exploit a natural experiment in Chile where topographic shielding by an upwind lava flow yields diverse erosional landforms in a downwind ignimbrite. Using a 3-D topographic wind model, we find that low velocities in the wake of a lava lobe coincide with a transition from landforms reflecting fracture-parallel erosion to flow-parallel erosion. Erosion rates across these landforms vary with shear velocity and abrasion susceptibility of the windward escarpment. We hypothesize that this morphologic threshold is controlled by whether particles can be lofted in suspension and overcome topographic steering imposed by fractured bedrock blocks. Within a phase space set by Rouse and Stokes numbers, our data illustrate that wind-abraded landforms reflect a competition between the material skeleton of the landscape and the strength of the flow that shapes it.
0094-8276
https://hdl.handle.net/10919/118090
https://doi.org/10.1029/2019GL083955
46
21
1944-8007
wind erosion
planetary landscape evolution
geomorphology
Atacama
Controls on Eolian Landscape Evolution in Fractured Bedrock
oai:vtechworks.lib.vt.edu:10919/1023752021-02-16T08:13:19Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Marsh, Adam D.
author
Smith, Matthew E.
author
Parker, William G.
author
Irmis, Randall B.
author
Kligman, Ben T.
author
2020-07-03
Acaenasuchus geoffreyi is a diminutive armored archosaur from the Upper Triassic Chinle Formation of northern Arizona, U.S.A., with uncertain evolutionary relationships and skeletal maturity. Known only from osteoderms, the taxon has been considered a valid taxon of aetosaur, juvenile specimens synonymous with the aetosaur Desmatosuchus spurensis, or a non-aetosaurian pseudosuchian archosaur. Here, we describe new fossils of Acaenasuchus geoffreyi that represent cranial, vertebral, and appendicular elements as well as previously unknown variations in the dorsal carapace and ventral shield. The skull bones are ornamented with the same anastomosing complex of ridges and grooves found on the paramedian and lateral osteoderms, and the appendicular skeleton resembles that of Revueltosaurus callenderi, Euscolosuchus olseni, aetosaurs, and other armored archosaurs such as erpetosuchids. Histology of osteoderms from the hypodigm of Acaenasuchus geoffreyi shows multiple growth lines, laminar tissue, and low vascularity, evidence that the individuals were close to skeletal maturity and not young juveniles. A revised phylogenetic analysis of early archosaurs recovers Acaenasuchus geoffreyi and Euscolosuchus olsenias sister taxa and members of a new clade that is the sister taxon of Aetosauria. This new phylogeny depicts a broader distribution of osteoderm character states previously thought to only occur in aetosaurs, demonstrating the danger of using only armor character states in aetosaur taxonomy and phylogeny. Acaenasuchus geoffreyi is also a good example of how new fossils can stabilize 'wild card' taxa in phylogenetic analyses and contributes to our understanding of the evolution of the aetosaur carapace.
0272-4634
e1794885
http://hdl.handle.net/10919/102375
https://doi.org/10.1080/02724634.2020.1794885
40
4
1937-2809
Skeletal Anatomy of Acaenasuchus Geoffreyi Long and Murry, 1995 (Archosauria: Pseudosuchia) and its Implications for the Origin of the Aetosaurian Carapace
oai:vtechworks.lib.vt.edu:10919/1054002021-10-19T07:11:53Zcom_10919_8195com_10919_25799com_10919_24209com_10919_5553col_10919_78797col_10919_24267
00925njm 22002777a 4500
dc
Lima, A.
author
Bodnar, Robert J.
author
De Vivo, B.
author
Spera, F. J.
author
Belkin, H. E.
author
2021-10-14
Several recent models that have been put forth to explain bradyseism at Campi Flegrei (CF), Italy, are discussed. Data obtained during long-term monitoring of the CF volcanic district has led to the development of a model based on lithological-structural and stratigraphic features that produce anisotropic and heterogeneous permeability features showing large variations both horizontally and vertically; these data are inconsistent with a model in which bradyseism is driven exclusively by shallow magmatic intrusions. CF bradyseism events are driven by cyclical magmatic-hydrothermal activity. Bradyseism events are characterized by cyclical, constant invariant signals repeating over time, such as area deformation along with a spatially well-defined seismogenic volume. These similarities have been defined as “bradyseism signatures” that allow us to relate the bradyseism with impending eruption precursors. Bradyseism is governed by an impermeable shallow layer (B-layer), which is the cap of an anticlinal geological structure culminating at Pozzuoli, where maximum uplift is recorded. This B-layer acts as a throttling valve between the upper aquifer and the deeper hydrothermal system that experiences short (1-102 yr) timescale fluctuations between lithostatic/hydrostatic pressure. The hydrothermal system also communicates episodically with a cooling and quasi-steady-state long timescale (103-104 yr) magmatic system enclosed by an impermeable carapace (A layer). Connectivity between hydrostatic and lithostatic reservoirs is episodically turned on and off causing alternatively subsidence (when the systems are connected) or uplift (when the systems are disconnected), depending on whether permeability by fractures is established or not. Earthquake swarms are the manifestation of hydrofracturing which allows fluid expansion; this same process promotes silica precipitation that seals cracks and serves to isolate the two reservoirs. Faults and fractures promote outgassing and reduce the vertical uplift rate depending on fluid pressure gradients and spatial and temporal variations in the permeability field. The miniuplift episodes also show “bradyseism signatures” and are well explained in the context of the short timescale process.
A. Lima, R. J. Bodnar, B. De Vivo, F. J. Spera, and H. E. Belkin, “Interpretation of Recent Unrest Events (Bradyseism) at Campi Flegrei, Napoli (Italy): Comparison of Models Based on Cyclical Hydrothermal Events versus Shallow Magmatic Intrusive Events,” Geofluids, vol. 2021, Article ID 2000255, 16 pages, 2021. doi:10.1155/2021/2000255
http://hdl.handle.net/10919/105400
https://doi.org/10.1155/2021/2000255
Interpretation of Recent Unrest Events (Bradyseism) at Campi Flegrei, Napoli (Italy): Comparison of Models Based on Cyclical Hydrothermal Events versus Shallow Magmatic Intrusive Events
oai:vtechworks.lib.vt.edu:10919/829152023-11-29T19:08:30Zcom_10919_78629com_10919_78628com_10919_8195com_10919_25799com_10919_5540com_10919_24227com_10919_5532com_10919_24209com_10919_5553com_10919_24213col_10919_78630col_10919_78882col_10919_71752col_10919_24302col_10919_24267col_10919_24334
00925njm 22002777a 4500
dc
VanDerwerker, Tiffany
author
Zhang, Lin
author
Ling, Erin
author
Benham, Brian L.
author
Schreiber, Madeline E.
author
2018-04-18
We investigated if geologic factors are linked to elevated arsenic (As) concentrations above 5 μg/L in well water in the state of Virginia, USA. Using geologic unit data mapped within GIS and two datasets of measured As concentrations in well water (one from public wells, the other from private wells), we evaluated occurrences of elevated As (above 5 μg/L) based on geologic unit. We also constructed a logistic regression model to examine statistical relationships between elevated As and geologic units. Two geologic units, including Triassic-aged sedimentary rocks and Triassic-Jurassic intrusives of the Culpeper Basin in north-central Virginia, had higher occurrences of elevated As in well water than other geologic units in Virginia. Model results support these patterns, showing a higher probability for As occurrence above 5 μg/L in well water in these two units. Due to the lack of observations (<5%) having elevated As concentrations in our data set, our model cannot be used to predict As concentrations in other parts of the state. However, our results are useful for identifying areas of Virginia, defined by underlying geology, that are more likely to have elevated As concentrations in well water. Due to the ease of obtaining publicly available data and the accessibility of GIS, this study approach can be applied to other areas with existing datasets of As concentrations in well water and accessible data on geology.
VanDerwerker, T.; Zhang, L.; Ling, E.; Benham, B.; Schreiber, M. Evaluating Geologic Sources of Arsenic in Well Water in Virginia (USA). Int. J. Environ. Res. Public Health 2018, 15, 787.
http://hdl.handle.net/10919/82915
https://doi.org/10.3390/ijerph15040787
Benham, Brian [0000-0002-3041-8999]
Ling, Erin [0000-0002-7817-7979]
Schreiber, Madeline [0000-0002-1858-7730]
groundwater management
drinking water
Water quality
statistical modeling
logistic regression
Evaluating Geologic Sources of Arsenic in Well Water in Virginia (USA)
oai:vtechworks.lib.vt.edu:10919/1180962024-03-18T13:12:29Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Zekkos, D.
author
Clark, M.
author
Willis, Michael J.
author
Athanasopoulos-Zekkos, A.
author
Manousakis, J.
author
Knoper, L.
author
Stahl, T.
author
Massey, C.
author
Archibald, G.
author
Greenwood, W.
author
Medwedeff, W.
author
2018-01-01
The ability to quickly, efficiently and reliably characterize changes in the landscape following an earthquake has remained a challenge for the earthquake engineering profession. The 2016 Mw7.8 Kaikoura earthquake provided a unique opportunity to document changes in topography following an earthquake on a regional scale using satellite derived high-resolution digital models. Along-track stereo satellite imagery had been collected for the pre-event topography. Satellites were tasked and collected stereo-mode post-event imagery. Both sets of images were used to create digital surface models (DSMs) of the affected area before and after the event. The procedure followed and indicative results for the Leader valley are presented with emphasis on the challenges associated with the implementation of the technique for the first time in this environment. The valley is of interest because of the variety of features it includes, i.e., the large Leader landslide, smaller landslides, stable sloping and flat ground as well as fault rupture lineaments. The open-source SETSM software is used to provide multiple DSMs. Our workflow is described and results are compared against the DSM created using Structure-from-Motion with imagery collected by Unmanned Aerial Vehicles (UAV) and aerial LIDAR. Overall, the sub-meter agreement between the DSM created using satellites and the DSM created using UAV and LIDAR datasets demonstrates viability for use in seismic studies, but features smaller than about 0.5 m are more difficult to discern.
9781510873254
https://hdl.handle.net/10919/118096
5
3D models of the leader valley using satellite & UAV imagery following the 2016 Kaikoura earthquake
oai:vtechworks.lib.vt.edu:10919/1180612024-03-18T13:21:24Zcom_10919_5com_10919_25799com_10919_23747com_10919_5539com_10919_24209com_10919_5553col_10919_70873col_10919_23748col_10919_24267
00925njm 22002777a 4500
dc
Hoagland, Steven
author
Irish, Jennifer L.
author
Weiss, Robert
author
2024-02
Recently developed models of coastal barrier morphodynamics include marsh and lagoon processes that have been shown to impact barrier island evolution. To gain additional insights into the simulated barrier-backbarrier system dynamics, this study explores the parameter space of a barrier evolution model using global sensitivity analysis. Influential parameters, their interactions with one another, and regions of sensitivity within the parameter space were identified using Sobol indices and factor mapping techniques for model results through the end of the century. The results of this study highlight an important relationship between initial and critical barrier island geometries and suggest that narrow and low-relief barriers are most vulnerable to be eroded away (width drowning) or overtaken by sea level rise (height drowning), respectively. Width drowning was also strongly associated with other model input parameters such as toe depth, sea level rise rate, and backbarrier critical bed shear stress, which suggests that sub-centennial drowning is dependent on a unique combination of input parameter values and may be averted (or delayed) with a single input parameter change. Barrier dynamics were significantly influenced by the backbarrier marsh platform, which was more impacted by sediment transport parameters such as critical bed shear stress and ocean sediment concentration than maximum annual overwash flux. This suggests that inorganic sediment deposition through tidal inlet dispersion is much more significant to the backbarrier marsh and lagoon system than overwash over sub-centennial timescales and can help to reduce the risk of width drowning.
0169-555X
https://hdl.handle.net/10919/118061
https://doi.org/10.1016/j.geomorph.2024.109087
Irish, Jennifer [0000-0002-2429-5953]
Hoagland, Steven [0000-0002-1133-0799]
Weiss, Robert [0000-0002-7168-5401]
Morphodynamic and modeling insights from global sensitivity analysis of a barrier island evolution model
oai:vtechworks.lib.vt.edu:10919/1173832024-01-18T03:01:45Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
King, Scott D.
author
2022-04-04
While volcanic landforms attest to the numerous and varied volcanic processes on Venus, estimates of the frequency of volcanic eruptions are lacking. Constraints from volcanic resurfacing volumes can be equally satisfied by infrequent large eruptions or numerous smaller events. Recently, Byrne and Krishnamoorthy (2022), https://doi.org/10.1029/2021JE007040, used the 40-year period from 1980 to 2020 from the Smithsonian Global Volcanism Program (GVP) database (Global Volcanism Program, 2013) to extrapolate the frequency of volcanic events on Earth to Venus. They evaluated the tectonic settings from the GVP database and provided estimates that consider the differences in those settings between Earth and Venus. Byrne and Krishnamoorthy extrapolated the rate of volcanism between Earth and Venus using the mass/volume ratios, freeing their results from the uncertain tectonic evolution of Venus. The assumption that Venus is in a stagnant-lid tectonic regime with a straight-forward geodynamic evolution has been challenged by Weller and Kiefer (2020), https://doi.org/10.1029/2019je005960, who showed that a planetary surface may reflect different styles of convection with highly active and sluggish and inactive regions occurring at the same time. The straight-forward scaling allowed Byrne and Krishnamoorthy to estimate that as many as 120 eruptions might take place on Venus every year, a frequency that should be detectable by upcoming Venus missions.
2169-9097
https://hdl.handle.net/10919/117383
https://doi.org/10.1029/2022JE007208
127
4
King, Scott [0000-0002-9564-5164]
2169-9100
Venus
volcanism
Volcanic Activity on Venus: How Long Must We Look to Find a Smoking Gun?
oai:vtechworks.lib.vt.edu:10919/1180862024-03-18T13:07:56Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Dufresne, A.
author
Geertsema, M.
author
Shugar, D. H.
author
Koppes, M.
author
Higman, B.
author
Haeussler, P. J.
author
Stark, C.
author
Venditti, J. G.
author
Bonno, D.
author
Larsen, C.
author
Gulick, S. P. S.
author
McCall, N.
author
Walton, M.
author
Loso, M. G.
author
Willis, Michael J.
author
2018-02
On 17 October 2015, a landslide of roughly 60 × 106 m3 occurred at the terminus of Tyndall Glacier in Taan Fiord, southeastern Alaska. It caused a tsunami that inundated an area over 20 km2, whereas the landslide debris itself deposited within a much smaller area of approximately 2 km2. It is a unique event in that the landslide debris was deposited into three very different environments: on the glacier surface, on land, and in the marine waters of the fjord. Part of the debris traversed the width of the fjord and re-emerged onto land, depositing coherent hummocks with preserved source stratigraphy on an alluvial fan and adjacent moraines on the far side of the fjord. Imagery from before the landslide shows that the catastrophic slope failure was preceded by deformation and sliding for at least the two decades since the glacier retreated to its current terminus location, exposing steep and extensively faulted slopes. A small volume of the total slide mass remains within the source area and is topped by striated blocks (> 10 m across) and standing trees that were transported down the slope in intact positions during the landslide. Field work was carried out in the summer of 2016, and by the time this paper was written, almost all of the supraglacial debris was advected into the fjord and half the subaerial hummocks were buried by glacial advance; this rapid change illustrates how highly active sedimentary processes in high-altitude glacial settings can skew any landslide-frequency analyses, and emphasizes the need for timely field investigations of these natural hazards.
0037-0738
https://hdl.handle.net/10919/118086
https://doi.org/10.1016/j.sedgeo.2017.10.004
364
1879-0968
Landslide
Sedimentology
Tsunami
Alaska
Periglacial
Sedimentology and geomorphology of a large tsunamigenic landslide, Taan Fiord, Alaska
oai:vtechworks.lib.vt.edu:10919/496532020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Sitepu, H.
author
2007-09
Transformation behaviors of the technologically important polycrystalline Ti50.75Ni47.75Fe1.50 shape memory alloy were investigated using differential scanning calorimeter (DSC) and powder diffraction techniques. DSC revealed that there are two-stage (i.e., cubic -> trigonal -> monoclinic) martensitic phase transformations on cooling and a one-step transformation (monoclinic -> cubic) on heating. In situ structural refinement of cubic -> trigonal -> monoclinic on cooling was carried out using the D1A high-resolution neutron powder diffractometer at the Institut Laue-Langevin Neutrons for Science in Grenoble, France. Results showed that the phases involved during the phase transition are consistent with the differential scanning calorimeter cooling curve, and the refined crystal structure parameters obtained from Rietveld refinements with the generalized spherical harmonic description agreed reasonably well with X-ray single-crystal data. Subsequently, a combined neutron and synchrotron structural refinement for each phase was conducted because the trial refinements initially using only the synchrotron data of trigonal phase yielded a false minimum with a somewhat high goodness-of-fit chi(2). Results obtained from the combined neutron and synchrotron data of the cubic, trigonal, and monoclinic phases show that the same minimum goodness-of-fit indices were always obtained. (C) 2007 International Centre for Diffraction Data.
Sitepu, H., "Structural refinement of neutron powder diffraction data of two-stage martensitic phase transformations in Ti50.75Ni47.75Fe1.50 shape memory alloy," Powder Diffr., Vol. 22, 2007. DOI: 10.1154/1.2754715
0885-7156
http://hdl.handle.net/10919/49653
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8503278&fulltextType=RA&fileId=S0885715600004176
https://doi.org/10.1154/1.2754715
neutron powder diffraction
generalized spherical harmonic
shape memory
alloy
ti-ni
martensitic transformation
quantitative texture analysis
preferred orientation
r-phase
rietveld
refinement
crystal-structure
percent-ni
intensities
synchrotron
molybdite
march
materials science, characterization & testing
Structural refinement of neutron powder diffraction data of two-stage martensitic phase transformations in Ti50.75Ni47.75Fe1.50 shape memory alloy
oai:vtechworks.lib.vt.edu:10919/874462020-10-22T05:00:53Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Zhang, Feifei
author
Xiao, Shuhai
author
Kendall, Brian
author
Romaniello, Stephen J.
author
Cui, Huan
author
Meyer, Mike
author
Gilleaudeau, Geoffrey J.
author
Kaufman, Alan J.
author
Anbar, Ariel D.
author
2018-06-20
The terminal Ediacaran Period witnessed the decline of the Ediacara biota (which may have included many stem-group animals). To test whether oceanic anoxia might have played a role in this evolutionary event, we measured U isotope compositions (δ238U) in sedimentary carbonates from the Dengying Formation of South China to obtain new constraints on the extent of global redox change during the terminal Ediacaran. We found the most negative carbonate δ238U values yet reported (−0.95 per mil), which were reproduced in two widely spaced coeval sections spanning the terminal Ediacaran Period (551 to 541 million years ago). Mass balance modeling indicates an episode of extensive oceanic anoxia, during which anoxia covered >21% of the seafloor and most U entering the oceans was removed into sediments below anoxic waters. The results suggest that an expansion of oceanic anoxia and temporal-spatial redox heterogeneity, independent of other environmental and ecological factors, may have contributed to the decline of the Ediacara biota and may have also stimulated animal motility.
http://hdl.handle.net/10919/87446
https://doi.org/10.1126/sciadv.aan8983
4
6
Extensive marine anoxia during the terminal Ediacaran Period
oai:vtechworks.lib.vt.edu:10919/1018872023-04-28T19:01:44Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Burkett, Corey A.
author
Bemis, Sean P.
author
Benowitz, Jeff A.
author
2016-12-14
The tallest mountain in North America, Denali (formerly Mount McKinley, 6,190 m), is situated inside an abrupt bend in the right-lateral strike-slip Denali fault. This anomalous topography is clearly associated with the complex geometry of the Denali fault, but how this restraining bend has evolved in conjunction with the regional topography is unknown. To constrain how this bend in the Denali fault is deforming, we document the Quaternary fault-related deformation north of the Denali fault through combined geologic mapping, active fault characterization, and analysis of background seismicity. Our mapping illustrates an east–west change in faulting style where normal faults occur east of the fault bend and thrust faults predominate to the west. The complex and elevated regional seismicity corroborates the style of faulting adjacent to the fault bend and provides additional insight into the change in local stress field in the crust adjacent to the bend. The style of active faulting and seismicity patterns define a deforming zone that accommodates the southwestward migration of this restraining bend. Fault slip rates for the active faults north of the Denali fault, derived from offset glacial outwash surfaces, indicate that the Mount McKinley restraining bend is migrating along the Denali fault at a late Pleistocene/Holocene rate of ~ 2–6 mm/yr. Ongoing thermochronologic and structural studies of the Mount McKinley restraining bend will extend these constraints on the migration and evolution of the restraining bend deeper in time and to the south of the Denali fault.
0040-1951
http://hdl.handle.net/10919/101887
https://doi.org/10.1016/j.tecto.2016.05.009
693
Bemis, Sean [0000-0001-7854-6394]
1879-3266
Physical Sciences
Geochemistry & Geophysics
Transpressional tectonics
Thrust fault
Denali National Park & Preserve
Restraining bend
Quaternary geology
STRIKE-SLIP-FAULT
RANGE
TECTONICS
EASTERN
DEFORMATION
EARTHQUAKE
BASIN
CONSTRAINTS
EXHUMATION
GLACIATION
0402 Geochemistry
0403 Geology
0404 Geophysics
Along-fault migration of the Mount McKinley restraining bend of the Denali fault defined by late Quaternary fault patterns and seismicity, Denali National Park & Preserve, Alaska
oai:vtechworks.lib.vt.edu:10919/1108322023-11-29T12:18:25Zcom_10919_5com_10919_25799com_10919_23829com_10919_5553com_10919_23967com_10919_5557com_10919_24209com_10919_24213col_10919_70873col_10919_23830col_10919_24279col_10919_24267col_10919_24334
00925njm 22002777a 4500
dc
Lewis, Abigail S. L.
author
Woelmer, Whitney M.
author
Wander, Heather L.
author
Howard, Dexter W.
author
Smith, John W.
author
McClure, Ryan P.
author
Lofton, Mary E.
author
Hammond, Nicholas W.
author
Corrigan, Rachel S.
author
Thomas, R. Quinn
author
Carey, Cayelan C.
author
2021-12-14
Near-term iterative forecasting is a powerful tool for ecological decision support and has the potential to transform our understanding of ecological predictability. However, to this point, there has been no cross-ecosystem analysis of near-term ecological forecasts, making it difficult to synthesize diverse research efforts and prioritize future developments for this emerging field. In this study, we analyzed 178 near-term (≤10-yr forecast horizon) ecological forecasting papers to understand the development and current state of near-term ecological forecasting literature and to compare forecast accuracy across scales and variables. Our results indicated that near-term ecological forecasting is widespread and growing: forecasts have been produced for sites on all seven continents and the rate of forecast publication is increasing over time. As forecast production has accelerated, some best practices have been proposed and application of these best practices is increasing. In particular, data publication, forecast archiving, and workflow automation have all increased significantly over time. However, adoption of proposed best practices remains low overall: for example, despite the fact that uncertainty is often cited as an essential component of an ecological forecast, only 45% of papers included uncertainty in their forecast outputs. As the use of these proposed best practices increases, near-term ecological forecasting has the potential to make significant contributions to our understanding of forecastability across scales and variables. In this study, we found that forecastability (defined here as realized forecast accuracy) decreased in predictable patterns over 1–7 d forecast horizons. Variables that were closely related (i.e., chlorophyll and phytoplankton) displayed very similar trends in forecastability, while more distantly related variables (i.e., pollen and evapotranspiration) exhibited significantly different patterns. Increasing use of proposed best practices in ecological forecasting will allow us to examine the forecastability of additional variables and timescales in the future, providing a robust analysis of the fundamental predictability of ecological variables.
1051-0761
http://hdl.handle.net/10919/110832
https://doi.org/10.1002/eap.2500
32
2
Thomas, Robert [0000-0003-1282-7825]
Carey, Cayelan [0000-0001-8835-4476]
34800082
1939-5582
data assimilation
decision support
ecological predictability
forecast automation
forecast evaluation
forecast horizon
forecast uncertainty
iterative forecasting
near-term forecast
null model
open science
uncertainty partitioning
OPPORTUNITIES
UNCERTAINTY
INFORMATION
POPULATION
PREDICTION
MODEL
Increased adoption of best practices in ecological forecasting enables comparisons of forecastability
oai:vtechworks.lib.vt.edu:10919/862692020-10-22T03:26:46Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Schwarzenbach, Esther M.
author
Caddick, Mark J.
author
Petroff, Matthew
author
Gill, Benjamin C.
author
Cooperdock, Emily H. G.
author
Barnes, Jaime D.
author
2018-10-19
Subduction zones impose an important control on the geochemical cycling between the surficial and internal reservoirs of the Earth. Sulphur and carbon are transferred into Earth's mantle by subduction of pelagic sediments and altered oceanic lithosphere. Release of oxidizing sulphate- and carbonate-bearing fluids modifies the redox state of the mantle and the chemical budget of subduction zones. Yet, the mechanisms of sulphur and carbon cycling within subduction zones are still unclear, in part because data are typically derived from arc volcanoes where fluid compositions are modified during transport through the mantle wedge. We determined the bulk rock elemental, and sulphur and carbon isotope compositions of exhumed ultramafic and metabasic rocks from Syros, Greece. Comparison of isotopic data with major and trace element compositions indicates seawater alteration and chemical exchange with sediment-derived fluids within the subduction zone channel. We show that small bodies of detached slab material are subject to metasomatic processes during exhumation, in contrast to large sequences of obducted ophiolitic sections that retain their seafloor alteration signatures. In particular, fluids circulating along the plate interface can cause sulphur mobilization during several stages of exhumation within high-pressure rocks. This takes place more pervasively in serpentinites compared to mafic rocks.
2045-2322
15517
http://hdl.handle.net/10919/86269
https://doi.org/10.1038/s41598-018-33610-9
8
30341323
microbial sulfate reduction
hosted hydrothermal systems
fluid-rock interaction
oceanic-crust
garnet growth
western alps
syros greece
serpentinites
isotope
cyclades
Sulphur and carbon cycling in the subduction zone melange
oai:vtechworks.lib.vt.edu:10919/1145342023-04-19T07:12:24Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Babakhani, Peyman
author
Phenrat, Tanapon
author
Baalousha, Mohammed
author
Soratana, Kullapa
author
Peacock, Caroline L.
author
Twining, Benjamin S.
author
Hochella, Michael F. Jr.
author
2022-12
This Analysis considers the potential benefits and challenges of applying engineered nanoparticles for artificial-ocean-fertilization-driven carbon sequestration Artificial ocean fertilization (AOF) aims to safely stimulate phytoplankton growth in the ocean and enhance carbon sequestration. AOF carbon sequestration efficiency appears lower than natural ocean fertilization processes due mainly to the low bioavailability of added nutrients, along with low export rates of AOF-produced biomass to the deep ocean. Here we explore the potential application of engineered nanoparticles (ENPs) to overcome these issues. Data from 123 studies show that some ENPs may enhance phytoplankton growth at concentrations below those likely to be toxic in marine ecosystems. ENPs may also increase bloom lifetime, boost phytoplankton aggregation and carbon export, and address secondary limiting factors in AOF. Life-cycle assessment and cost analyses suggest that net CO2 capture is possible for iron, SiO2 and Al2O3 ENPs with costs of 2-5 times that of conventional AOF, whereas boosting AOF efficiency by ENPs should substantially enhance net CO2 capture and reduce these costs. Therefore, ENP-based AOF can be an important component of the mitigation strategy to limit global warming.
http://hdl.handle.net/10919/114534
https://doi.org/10.1038/s41565-022-01226-w
17
12
36443601
1748-3395
Oxide nanoparticles
iron fertilization
nanotechnology
stabilization
opportunities
growth
export
fate
zinc
Potential use of engineered nanoparticles in ocean fertilization for large-scale atmospheric carbon dioxide removal
oai:vtechworks.lib.vt.edu:10919/816082023-04-14T17:49:49Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Stocker, Michelle R.
author
Lessner, Emily J.
author
Smith, Nathan D.
author
Turner, Alan H.
author
Irmis, Randall B.
author
Nesbitt, Sterling J.
author
2016-09-06
Rauisuchids are large (2–6 m in length), carnivorous, and quadrupedal pseudosuchian archosaurs closely related to crocodylomorphs. Though geographically widespread, fossils of this clade are relatively rare in Late Triassic assemblages. The middle Norian (∼212 Ma) Hayden Quarry of northern New Mexico, USA, in the Petrified Forest Member of the Chinle Formation, has yielded isolated postcranial elements and associated skull elements of a new species of rauisuchid. Vivaron haydeni gen. et. sp. nov. is diagnosed by the presence of two posteriorly directed prongs at the posterior end of the maxilla for articulation with the jugal. The holotype maxilla and referred elements are similar to those of the rauisuchid Postosuchus kirkpatricki from the southwestern United States, but V. haydeni shares several maxillary apomorphies (e.g., a distinct dropoff to the antorbital fossa that is not a ridge, a straight ventral margin, and a well defined dental groove) with the rauisuchid Teratosaurus suevicus from the Norian of Germany. Despite their geographic separation, this morphological evidence implies a close phylogenetic relationship between V. haydeni and T. suevicus. The morphology preserved in the new Hayden Quarry rauisuchid V. haydeni supports previously proposed and new synapomorphies for nodes within Rauisuchidae. The discovery of Vivaron haydeni reveals an increased range of morphological disparity for rauisuchids from the low-paleolatitude Chinle Formation and a clear biogeographic connection with high paleolatitude Pangea.
http://hdl.handle.net/10919/81608
https://doi.org/10.7717/peerj.2336
27651983
Teratosaurus
Postosuchus
Rauisuchidae
Hayden Quarry
Evolutionary Studies
Paleontology
A new rauisuchid (Archosauria, Pseudosuchia) from the Upper Triassic (Norian) of New Mexico increases the diversity and temporal range of the clade
oai:vtechworks.lib.vt.edu:10919/1030262023-04-28T19:01:47Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
King, Scott D.
author
Adam, Claudia
author
2014-10-01
The first attempts to quantify the width and height of hotspot swells were made more than 30. years ago. Since that time, topography, ocean-floor age, and sediment thickness datasets have improved considerably. Swell heights and widths have been used to estimate the heat flow from the core-mantle boundary, constrain numerical models of plumes, and as an indicator of the origin of hotspots. In this paper, we repeat the analysis of swell geometry and buoyancy flux for 54. hotspots, including the 37 considered by Sleep (1990) and the 49 considered by Courtillot et al. (2003), using the latest and most accurate data. We are able to calculate swell geometry for a number of hotspots that Sleep was only able to estimate by comparison with other swells. We find that in spite of the increased resolution in global bathymetry models there is significant uncertainty in our calculation of buoyancy fluxes due to differences in our measurement of the swells' width and height, the integration method (volume integration or cross-sectional area), and the variations of the plate velocities between HS2-Nuvel1a (Gripp and Gordon, 1990) and HS3-Nuvel1a (Gripp and Gordon, 2002). We also note that the buoyancy flux for Pacific hotspots is in general larger than for Eurasian, North American, African and Antarctic hotspots. Considering that buoyancy flux is linearly related to plate velocity, we speculate that either the calculation of buoyancy flux using plate velocity over-estimates the actual vertical flow of material from the deep mantle or that convection in the Pacific hemisphere is more vigorous than the Atlantic hemisphere. © 2014 Elsevier B.V.
0031-9201
AQ7ST (isidoc)
http://hdl.handle.net/10919/103026
https://doi.org/10.1016/j.pepi.2014.07.006
235
King, Scott [0000-0002-9564-5164]
1872-7395
Physical Sciences
Geochemistry & Geophysics
Hotspot swells
Depth anomalies
Buoyancy flux
Heat flow
SOUTH-PACIFIC SUPERSWELL
MANTLE PLUMES
TRANSITION ZONE
HEAT-FLOW
OCEANIC LITHOSPHERE
STRUCTURE BENEATH
PLATE VELOCITIES
ORIGIN
MODELS
SUBSIDENCE
0201 Astronomical and Space Sciences
0402 Geochemistry
0404 Geophysics
Geochemistry & Geophysics
Hotspot swells revisited
oai:vtechworks.lib.vt.edu:10919/1049192023-11-29T19:08:55Zcom_10919_5540com_10919_24209com_10919_5553col_10919_71752col_10919_24267
00925njm 22002777a 4500
dc
To, Khanh H.T.
author
O’Brien, H.D.
author
Stocker, Michelle R.
author
Gignac, P.M.
author
2021
Dietary requirements and acquisition strategies change throughout ontogeny across various clades of tetrapods, including birds. For example, birds hatch with combinations of various behavioral, physiological, and morphological factors that place them on an altricial– precocial spectrum. Passeriformes (songbirds) in particular, a family constituting approximately more than half of known bird species, displays the most drastic difference between hatchling and adults in each of these aspects of their feeding biology. How the shift in dietary resource acquisition is managed during ontogeny alongside its relationship to the morphology of the feeding apparatus has been largely understudied within birds. Such efforts have been hampered partly due to the small size of many birds and the diminutive jaw musculature they employ. In this study, we used standard and diffusible iodinebased contrast-enhanced computed tomography in conjunction with digital dissection to quantify and describe the cranial musculature of the Black-throated Finch (Poephila cincta) at fledgling and adult stages. Our results reveal that in both the fledgling and the adult, cranial musculature shows clear and complex partitioning in the Musculus adductor mandibulae externus that is consistent with other families within Passeriformes. We quantified jaw-muscle sizes and found that the adult showed a decrease in muscle mass in comparison to the fledgling individual. We propose that this could be the result of low sample size or a physiological effect of parental care in Passeriformes. Our study shows that high-resolution visualization techniques are informative at revealing morphological discrepancies for studies that involve small specimens such as Passeriformes especially with careful specimen selection criteria.
http://hdl.handle.net/10919/104919
https://doi.org/10.1093/iob/obab007
3
1
Cranial Musculoskeletal Description of Black-Throated Finch (Aves: Passeriformes: Estrildidae) with DiceCT
oai:vtechworks.lib.vt.edu:10919/749062024-03-13T14:09:39Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Parsons, A. J.
author
Law, R. D.
author
Lloyd, G. E.
author
Phillips, R. J.
author
Searle, M. P.
author
2016-04-01
1525-2027
http://hdl.handle.net/10919/74906
https://doi.org/10.1002/2015GC006184
17
4
Geochemistry & Geophysics
C-AXIS FABRICS
MAIN CENTRAL THRUST
CRYSTALLOGRAPHIC PREFERRED ORIENTATION
DISSOLUTION-PRECIPITATION CREEP
PARALLEL SUBGRAIN BOUNDARIES
STRAIN TORSION EXPERIMENTS
CRUSTAL CHANNEL FLOWS
DYNAMIC RECRYSTALLIZATION
PLASTIC-DEFORMATION
SLIP SYSTEMS
Thermo-kinematic evolution of the Annapurna-Dhaulagiri Himalaya, central Nepal: The Composite Orogenic System
oai:vtechworks.lib.vt.edu:10919/1069212021-12-11T08:11:12Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Sherpa, Sonam Futi
author
Shirzaei, Manoochehr
author
2021-11-24
Extreme precipitation and flooding often lead to human and economic losses. However, the high-resolution nationwide flooding exposure data are scarce. Availability of all-weather space-borne SAR satellite data can potentially improve the ability to generate high-resolution flood map extent and exposure globally. In Iran, flooding is a major concern, given the socioeconomic vulnerabilities and increased likelihood of climate extremes. Iran experienced extreme flooding during January to March 2019, attributed to significant precipitation during October 2018 to March 2019, which is well above the long-term averages for 1999-2019. Using Pettitt and Mann Kendall tests, nationwide precipitation records were identified by significant decreasing and increasing trends in north and south, respectively. Utilizing 673 Sentinel-1 SAR intensity images, we applied a fast-marching algorithm for image segmentation in combination with a Bayesian framework to obtain high-resolution probabilistic flood maps. We found, 22, 9, and 15 states in January, February, and March, respectively, experienced flooding that covered >15% of their area with high flooded area percent in the northwestern and southeastern region. We estimated that >15, >11.32, and >11.33 million people were exposed to floods in January, February, and March, respectively. Our datasets inform flooding models and management efforts under increasing climate extremes and changing land use and cover.
1753-318X
e12770
http://hdl.handle.net/10919/106921
https://doi.org/10.1111/jfr3.12770
2019 Iran flood
fast marching algorithm
precipitation analysis
probabilistic flood map exposure
synthetic aperture radar (SAR)
Country-wide flood exposure analysis using Sentinel-1 synthetic aperture radar data: Case study of 2019 Iran flood
oai:vtechworks.lib.vt.edu:10919/932502021-06-21T19:11:44Zcom_10919_8195com_10919_25799com_10919_24209com_10919_5553col_10919_79698col_10919_24267
00925njm 22002777a 4500
dc
Moncada, Daniel
author
Bodnar, Robert J.
author
2012-05-13
Successful exploration for mineral deposits requires tools that the explorationist can use to distinguish between targets with high potential for mineralization and those with lower economic potential. In this study, we describe a technique based on gangue mineral textures and fluid inclusion characteristics that has been applied to identify an area of high potential for gold-silver mineralization in the epithermal Ag-Au deposits at Guanajuato, Mexico. The Guanajuato mining district in Mexico is one of the largest silver producing districts in the world with continuous mining activity for nearly 500 years. Previous work conducted on the Veta Madre vein system that is located in the central part of this district identified favorable areas for further exploration in the deepest levels that have been developed and explored. The resulting exploration program discovered one of the richest gold-silver veins ever found in the district. This newly discovered vein that runs parallel to the Veta Madre was named the Santa Margarita vein. Selected mineralized samples from this vein contain up to 249 g/t of Au and up to 2,280 g/t Ag. Fluid inclusions in these samples show homogenization temperatures that range from 184 to 300°C and salinities ranging from 0 to 5 wt.% NaCl. Barren samples show the same range in homogenization temperature, but salinities range only up to 3 wt.% NaCl. Evidence of boiling was observed in most of the samples based on fluid inclusions and/or quartz and calcite textures. Liquid-rich inclusions with trapped illite are closely associated with high silver grades. The presence of assemblages of vapor-rich-only fluid inclusions, indicative of intense boiling or “flashing”, shows the best correlation with high gold grades.
http://hdl.handle.net/10919/93250
https://doi.org/10.2478/s13533-011-0057-8
4
2
Guanajuato Mining District
Veta Madre
fluid inclusions
boiling
flashing
mineral exploration
epithermal precious metals deposits
Gangue mineral textures and fluid inclusion characteristics of the Santa Margarita Vein in the Guanajuato Mining District, Mexico
oai:vtechworks.lib.vt.edu:10919/743092023-04-18T18:48:40Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Chen, Z.
author
Zhou, C.
author
Xiao, S.
author
Wang, W.
author
Guan, C.
author
Hua, H.
author
Yuan, X.
author
2014-02-25
Ediacara fossils are central to our understanding of animal evolution on the eve of the Cambrian explosion, because some of them likely represent stem-group marine animals. However, some of the iconic Ediacara fossils have also been interpreted as terrestrial lichens or microbial colonies. Our ability to test these hypotheses is limited by a taphonomic bias that most Ediacara fossils are preserved in sandstones and siltstones. Here we report several iconic Ediacara fossils and an annulated tubular fossil (reconstructed as an erect epibenthic organism with uniserial arranged modular units), from marine limestone of the 551-541 Ma Dengying Formation in South China. These fossils significantly expand the ecological ranges of several key Ediacara taxa and support that they are marine organisms rather than terrestrial lichens or microbial colonies. Their close association with abundant bilaterian burrows also indicates that they could tolerate and may have survived moderate levels of bioturbation.
Chen, Z.; Zhou, C. M.; Xiao, S. H.; Wang, W.; Guan, C. G.; Hua, H.; Yuan, X. L., "New Ediacara fossils preserved in marine limestone and their ecological implications," Scientific Reports 4:4180, (2014). DOI: 10.1038/srep04180.
2045-2322
http://hdl.handle.net/10919/74309
https://doi.org/10.1038/srep04180
4
SOUTH-AUSTRALIA COASTAL
YANGTZE GORGES AREA
MACKENZIE MOUNTAINS
NORTHWESTERN CANADA
TRACE FOSSIL
GAOJIASHAN LAGERSTATTE
DENGYING FORMATION
MICROBIAL MATS
DEEP MARINE
CHINA
New Ediacara fossils preserved in marine limestone and their ecological implications
oai:vtechworks.lib.vt.edu:10919/1177322024-01-30T09:38:17Zcom_10919_5com_10919_25799com_10919_23842com_10919_5553com_10919_24209com_10919_51731com_10919_5478com_10919_24369com_10919_5539col_10919_70873col_10919_23843col_10919_24267col_10919_51732col_10919_24370
00925njm 22002777a 4500
dc
Zhang, Yuxin
author
Hu, Anyang
author
Xia, Dawei
author
Hwang, Sooyeon
author
Sainio, Sami
author
Nordlund, Dennis
author
Michel, F. Marc
author
Moore, Robert B.
author
Li, Luxi
author
Lin, Feng
author
2023-07
Mn dissolution has been a long-standing, ubiquitous issue that negatively impacts the performance of Mn-based battery materials. Mn dissolution involves complex chemical and structural transformations at the electrode–electrolyte interface. The continuously evolving electrode–electrolyte interface has posed great challenges for characterizing the dynamic interfacial process and quantitatively establishing the correlation with battery performance. In this study, we visualize and quantify the temporally and spatially resolved Mn dissolution/redeposition (D/R) dynamics of electrochemically operating Mn-containing cathodes. The particle-level and electrode-level analyses reveal that the D/R dynamics is associated with distinct interfacial degradation mechanisms at different states of charge. Our results statistically differentiate the contributions of surface reconstruction and Jahn–Teller distortion to the Mn dissolution at different operating voltages. Introducing sulfonated polymers (Nafion) into composite electrodes can modulate the D/R dynamics by trapping the dissolved Mn species and rapidly establishing local Mn D/R equilibrium. This work represents an inaugural effort to pinpoint the chemical and structural transformations responsible for Mn dissolution via an operando synchrotron study and develops an effective method to regulate Mn interfacial dynamics for improving battery performance.
1748-3387
10.1038/s41565-023-01367-6 (PII)
https://hdl.handle.net/10919/117732
https://doi.org/10.1038/s41565-023-01367-6
18
7
Michel, Frederick [0000-0003-2817-980X]
Moore, Robert [0000-0001-9057-7695]
Lin, Feng [0000-0002-3729-3148]
37081082
1748-3395
Operando characterization and regulation of metal dissolution and redeposition dynamics near battery electrode surface
oai:vtechworks.lib.vt.edu:10919/1162622023-09-12T07:12:21Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Song, Huyue
author
An, Zhihui
author
Ye, Qin
author
Stueken, Eva E.
author
Li, Jing
author
Hu, Jun
author
Algeo, Thomas J.
author
Tian, Li
author
Chu, Daoliang
author
Song, Haijun
author
Xiao, Shuhai
author
Tong, Jinnan
author
2023-04
Based on geochemical and paleontological data, this study shows that habitable open-oceans extended to mid-latitude coastal oceans during the waning stage of the Marinoan snowball Earth, offering refugia for benthic photosynthetic eukaryotes During the Marinoan Ice Age (ca. 654-635 Ma), one of the 'Snowball Earth' events in the Cryogenian Period, continental icesheets reached the tropical oceans. Oceanic refugia must have existed for aerobic marine eukaryotes to survive this event, as evidenced by benthic phototrophic macroalgae of the Songluo Biota preserved in black shales interbedded with glacial diamictites of the late Cryogenian Nantuo Formation in South China. However, the environmental conditions that allowed these organisms to thrive are poorly known. Here, we report carbon-nitrogen-iron geochemical data from the fossiliferous black shales and adjacent diamictites of the Nantuo Formation. Iron-speciation data document dysoxic-anoxic conditions in bottom waters, whereas nitrogen isotopes record aerobic nitrogen cycling perhaps in surface waters. These findings indicate that habitable open-ocean conditions were more extensive than previously thought, extending into mid-latitude coastal oceans and providing refugia for eukaryotic organisms during the waning stage of the Marinoan Ice Age.
1564
http://hdl.handle.net/10919/116262
https://doi.org/10.1038/s41467-023-37172-x
14
1
37015913
2041-1723
cryogenian nantuo formation
ferruginous conditions
nitrogen isotopes
earth
climate
proxies
ocean
rise
iron
age
Mid-latitudinal habitable environment for marine eukaryotes during the waning stage of the Marinoan snowball glaciation
oai:vtechworks.lib.vt.edu:10919/1037612021-10-08T16:43:35Zcom_10919_78629com_10919_78628com_10919_8195com_10919_25799com_10919_24209com_10919_5553col_10919_78630col_10919_78882col_10919_24267
00925njm 22002777a 4500
dc
Ziegler, Brady A.
author
Ng, G.-H. Crystal
author
Cozzarelli, Isabelle M.
author
Dunshee, Aubrey J.
author
Schreiber, Madeline E.
author
2021-05-26
We used a reactive transport model to investigate the cycling of geogenic arsenic (As) in a petroleum-contaminated aquifer. We simulated As mobilization and sequestration using surface complexation reactions with Fe(OH)<sub>3</sub> during petroleum biodegradation coupled with Fe-reduction. Model results predict that dissolved As in the plume will exceed the U.S. and EU 10 µg/L drinking water standard for ~400 years. Non-volatile dissolved organic carbon (NVDOC) in the model promotes As mobilization by exerting oxygen demand, which maintains anoxic conditions in the aquifer. After NVDOC degrades, As re-associates with Fe(OH)<sub>3</sub> as oxygenated conditions are re-established. Over the 400-year simulation, As transport resembles a “roll front” in which: (1) arsenic sorbed to Fe(OH)<sub>3</sub> is released during Fe-reduction coupled to petroleum biodegradation; (2) dissolved As resorbs to Fe(OH)<sub>3</sub> at the plume’s leading edge; and (3) over time, the plume expands, and resorbed As is re-released into groundwater. This “roll front” behavior underscores the transience of sorption as an As attenuation mechanism. Over the plume’s lifespan, simulations suggest that As will contaminate more groundwater than benzene from the oil spill. At its maximum, the model simulates that ~5.7× more groundwater will be contaminated by As than benzene, suggesting that As could pose a greater long-term water quality threat than benzene in this petroleum-contaminated aquifer.
Ziegler, B.A.; Ng, G.-H.C.; Cozzarelli, I.M.; Dunshee, A.J.; Schreiber, M.E. Arsenic in Petroleum-Contaminated Groundwater near Bemidji, Minnesota Is Predicted to Persist for Centuries. Water 2021, 13, 1485.
http://hdl.handle.net/10919/103761
https://doi.org/10.3390/w13111485
arsenic
surface complexation
oil
biodegradation
iron reduction
sorption
reactive transport modeling
Arsenic in Petroleum-Contaminated Groundwater near Bemidji, Minnesota Is Predicted to Persist for Centuries
oai:vtechworks.lib.vt.edu:10919/1148302023-11-29T15:23:10Zcom_10919_24209com_10919_5553com_10919_110083col_10919_24267col_10919_110084
00925njm 22002777a 4500
dc
Sherpa, Sonam Futi
author
Shirzaei, Manoochehr
author
Ojha, Chandrakanta
author
2023-04
Future projections of sea-level rise (SLR) used to assess coastal flooding hazards and exposure throughout the 21st century and devise risk mitigation efforts often lack an accurate estimate of coastal vertical land motion (VLM) rate, driven by anthropogenic or non-climate factors in addition to climatic factors. The Chesapeake Bay (CB) region of the United States is experiencing one of the fastest rates of relative sea-level rise on the Atlantic coast of the United States. This study uses a combination of space-borne Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS), Light Detecting and Ranging (LiDAR) data sets, available National Oceanic and Atmospheric Administration (NOAA) long-term tide gauge data, and SLR projections from the Intergovernmental Panel on Climate Change (IPCC), AR6 WG1 to quantify the regional rate of relative SLR and future flooding hazards for the years 2030, 2050, and 2100. By the year 2100, the total inundated areas from SLR and subsidence are projected to be 454(316–549)–600(535𝐴𝐴–690) km² for Shared Socioeconomic Pathways (SSPs) 1–1.9 to 5–8.5, respectively, and 342(132–552)–627(526–735) 𝐴𝐴 km2 only from SLR. The effect of storm surges based on Hurricane Isabel can increase the inundated area to 849(832–867)–1,117(1,054–1,205) km² under different VLM and SLR scenarios. We suggest that accurate estimates of VLM rate, such as those obtained here, are essential to revise IPCC projections and obtain accurate maps of coastal flooding and inundation hazards. The results provided here inform policymakers when assessing hazards associated with global climate changes and local factors in CB, required for developing risk management and disaster resilience plans.
http://hdl.handle.net/10919/114830
https://doi.org/10.1002/essoar.10511192.1
Disruptive Role of Vertical Land Motion in Future Assessments of Climate Change-Driven Sea-Level Rise and Coastal Flooding Hazards in the Chesapeake Bay
oai:vtechworks.lib.vt.edu:10919/743082023-04-18T18:48:20Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Ou, Q.
author
Xiao, S.
author
Han, J.
author
Sun, G.
author
Zhang, F.
author
Zhang, Z.
author
Shu, D.
author
2015-07
Ctenophores are traditionally regarded as "lower" metazoans, sharing with cnidarians a diploblastic grade of organization. Unlike cnidarians, where skeletonization (biomineralization and sclerotization) evolved repeatedly among ecologically important taxa (for example, scleractinians and octocorals), living ctenophores are characteristically soft-bodied animals. We report six sclerotized and armored ctenophores from the early Cambrian period. They have diagnostic ctenophore features (for example, an octamerous symmetry, oral-aboral axis, aboral sense organ, and octaradially arranged ctene rows). Unlike most modern counterparts, however, they lack tentacles, have a sclerotized framework, and have eight pairs of ctene rows. They are resolved as a monophyletic group (Scleroctenophora new class) within the ctenophores. This clade reveals a cryptic history and sheds new light on the early evolution of this basal animal phylum. Skeletonization also occurs in some other Cambrian animal groups whose extant members are exclusively soft-bodied, suggesting the ecological importance of skeletonization in the Cambrian explosion.
http://hdl.handle.net/10919/74308
https://doi.org/10.1126/sciadv.1500092
1
6
Cambrian
Chengjiang biota
Ctenophora
skeleton
A vanished history of skeletonization in Cambrian comb jellies
oai:vtechworks.lib.vt.edu:10919/1177382024-01-30T14:10:12Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Nesbitt, Sterling J.
author
Chatterjee, Sankar
author
2024-01-23
A vast array of pseudosuchian body plans evolved during the diversification of the group in the Triassic Period, but few can compare to the toothless, long-necked, and bipedal shuvosaurids. Members of this clade possess theropod-like character states mapped on top of more plesiomorphic pseudosuchian character states, complicating our understanding of the evolutionary history of the skeleton. One taxon in this clade, Shuvosaurus inexpectatus has been assigned to various theropod dinosaur groups based on a partial skull and referred material and its postcranium was assigned to a different taxon in Pseudosuchia. After the discovery of a skeleton of a shuvosaurid with a Shuvosaurus-like skull and a pseudosuchian postcranial skeleton, it became clear Shuvosaurus inexpectatus was a pseudosuchian. Nevertheless, a number of questions have arisen about what skeletal elements belonged to Shuvosaurus inexpectatus, the identification of skull bones, and the resulting implication for pseudosuchian evolution. Here, we detail the anatomy of the skeleton Shuvosaurus inexpectatus through a critical lens, parse out the bones that belong to the taxon or those that clearly do not or may not belong to the taxon, rediagnose the taxon based on these revisions, and compare the taxon to other archosaurs. We find that Shuvosaurus inexpectatus possesses similar anatomy to other shuvosaurids but parts of the skeleton of the taxon clarifies the anatomy of the group given that they are preserved in Shuvosaurus inexpectatus but not in others. Shuvosaurus inexpectatus is represented by at least 14 individuals from the West Texas Post Quarry (Adamanian holochronozone) and all Shuvosaurus inexpectatus skeletal material from the locality pertains to skeletally immature individuals. All of the skeletons are missing most of the neural arches, ribs, and most of the forelimb. We only recognize Shuvosaurus inexpectatus from the Post Quarry and all other material assigned to the taxon previously is better assigned to the broader group Shuvosauridae.
1932-8486
https://hdl.handle.net/10919/117738
https://doi.org/10.1002/ar.25376
Nesbitt, Sterling [0000-0002-7017-1652]
38258540
1932-8494
Archosauria
convergence
Dockum Group
Norian
Poposauroidea
Shuvosauridae
The osteology of <i>Shuvosaurus inexpectatus</i>, a shuvosaurid pseudosuchian from the Upper Triassic Post Quarry, Dockum Group of Texas, USA
oai:vtechworks.lib.vt.edu:10919/972302021-03-24T13:27:25Zcom_10919_24209com_10919_5553com_10919_96735com_10919_23765col_10919_24267col_10919_96736
00925njm 22002777a 4500
dc
Cui, H.
author
Kaufman, Alan J.
author
Xiao, S.
author
Grazhdankin, D. V.
author
Peek, S.
author
Martin, A. J.
author
Bykova, N. V.
author
Rogov, V. I.
author
Liu, X. M.
author
Zhang, F.
author
Romaniello, S. J.
author
Anbar, A. D.
author
Peng, Y.
author
Cai, Y.
author
Schiffbauer, J. D.
author
Meyer, M.
author
Gilleaudeau, Geoffrey J.
author
Plummer, Rebecca E.
author
Sievers, N. E.
author
Goderis, S.
author
Claeys, P.
author
2019-11-22
The terminal Ediacaran contains dramatic changes in biogeochemical cycles, many of which are closely coupled with evolutionary transitions in the corresponding fossil records. Dynamic redox conditions may have caused a profound impact on early animal evolution. Our work highlights the significance of integrated bio-, litho-, and chemo-stratigraphy in geobiology research of the deep time.
0367-0449
e097
http://hdl.handle.net/10919/97230
https://doi.org/10.3989/egeol.43586.552
75
2
1988-3250
Chemostratigraphy
Redox condition
Early macroorganisms
Biogeochemical cycles
Geobiology
Animal biomineralization
Alkalinity
Cloudina
Recent advances in understanding the terminal Ediacaran Earth-life system in South China and Arctic Siberia
oai:vtechworks.lib.vt.edu:10919/1027222022-02-26T22:22:44Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Bemis, Sean P.
author
Scharer, Kate
author
Dolan, James
author
2021-03-05
This dataset consists of the electronic supplement for Bemis et al. (2021) published in the Bulletin of the Seismological Society of America. The files shared through the BSSA website have been saved at a reduced resolution to meet their file size limitation. This is a duplicate of that archive, but these files are saved at a higher resolution to ensure this data is universally accessible and permanently archived.
http://hdl.handle.net/10919/102722
Bemis, Sean [0000-0001-7854-6394]
paleoseismology
San Andreas fault
fault
earthquake
High-Resolution Electronic Supplement for "The San Andreas Fault paleoseismic record at Elizabeth Lake: Why are there fewer surface-rupturing earthquakes on the Mojave section?"
oai:vtechworks.lib.vt.edu:10919/985092020-10-22T03:35:55Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Bauer, Dustin B.
author
Hubbard, Stephen M.
author
Covault, Jacob A.
author
Romans, Brian W.
author
2020-01-23
A shelf-margin depositional system is the stratigraphic product of terrigenous sediment delivery to the ocean, comprising a flat to low-gradient shelf, or topset, which transitions to a steeper deep-water slope, and, ultimately, a relatively flat basin floor, or bottomset. Erosional and depositional processes across these physiographic domains approximate a clinoform in the stratigraphic record. The shelf margin is a critical environment for terrigenous sediment dispersal because it is a process-regime boundary that links the shelf to deep water and is a marker of basin evolution through time. Additionally, the coarse-grained deposits of strata associated with the shelf-margin zone are important subsurface reservoirs or aquifers. Here, we characterize the shelf-margin and upper slope stratigraphy of the outcropping Upper Cretaceous Tres Pasos and Dorotea formations, Magallanes Basin, southern Chile. The Late Cretaceous Magallanes retroarc foreland basin was an elongate trough oriented parallel to the southern Andean arc and fold-and-thrust belt. The Tres Pasos and Dorotea formations record southward (basin axial) progradation of a high-relief shelf and slope system (>1000 m paleo-water depth) represented by a stratigraphic succession up to 3 km thick that is exposed for tens of kilometers along depositional dip. The character and distribution of deposits that define shelf margins contain evidence for a variety of processes related to deposition, erosion, sediment bypass, and mass wasting. The overall architecture of the Magallanes Basin strata is indicative of a graded shelf-margin system interrupted by periods of slope oversteepening and development of out-of-grade conditions. These punctuated periods are recognized by sedimentological evidence for enhanced bypass of coarse-grained sediment across the upper slope, and thick submarine fan successions in more distal segments. Development of oversteepened depositional topography is particularly significant as it instigated the only two major periods of coarse-grained sediment delivery to deep water over similar to 8 Myr during the Campanian. The controls on sediment dispersal beyond the shelf margin are commonly discussed in terms of allogenic forcings, such as tectonics, climate, eustasy, and receiving-basin geometry, as well as autogenic behavior, such as delta-lobe switching. However, inherited depositional topography does not clearly fit within an allogenic/autogenic dichotomy. Depositional topography inherited from shelf-margin evolution influences the position of subsequent shelf margins, which can promote coarse-grained sediment delivery to deep water.
358
http://hdl.handle.net/10919/98509
https://doi.org/10.3389/feart.2019.00358
7
2296-6463
stratigraphy
clinoform
basin evolution
clastic sedimentology
Magallanes Basin
Inherited Depositional Topography Control on Shelf-Margin Oversteepening, Readjustment, and Coarse-Grained Sediment Delivery to Deep Water, Magallanes Basin, Chile
oai:vtechworks.lib.vt.edu:10919/1177342024-01-30T09:38:39Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Nicholas, Thomas C.
author
Stones, Adam Edward
author
Patel, Adam
author
Michel, F. Marc
author
Reeder, Richard J.
author
Aarts, Dirk G. A. L.
author
Deringer, Volker L.
author
Goodwin, Andrew L.
author
2023-09-25
Amorphous calcium carbonate is an important precursor for biomineralization in marine organisms. Key outstanding problems include understanding the structure of amorphous calcium carbonate and rationalizing its metastability as an amorphous phase. Here we report high-quality atomistic models of amorphous calcium carbonate generated using state-of-the-art interatomic potentials to help guide fits to X-ray total scattering data. Exploiting a recently developed inversion approach, we extract from these models the effective Ca⋯Ca interaction potential governing the structure. This potential contains minima at two competing distances, corresponding to the two different ways that carbonate ions bridge Ca2+-ion pairs. We reveal an unexpected mapping to the Lennard-Jones–Gauss model normally studied in the context of computational soft matter. The empirical model parameters for amorphous calcium carbonate take values known to promote structural complexity. We thus show that both the complex structure and its resilience to crystallization are actually encoded in the geometrically frustrated effective interactions between Ca2+ ions. [Figure not available: see fulltext.]
1755-4330
10.1038/s41557-023-01339-2 (PII)
https://hdl.handle.net/10919/117734
https://doi.org/10.1038/s41557-023-01339-2
16
1
Michel, Frederick [0000-0003-2817-980X]
37749235
1755-4349
Geometrically frustrated interactions drive structural complexity in amorphous calcium carbonate
oai:vtechworks.lib.vt.edu:10919/884772023-12-11T11:08:39Zcom_10919_8195com_10919_25799com_10919_24209com_10919_5553col_10919_18629col_10919_24267
00925njm 22002777a 4500
dc
Schindler, Michael
author
Mantha, Haley
author
Hochella, Michael F. Jr.
author
2019-03-13
Mineralogical studies of contaminated soils affected by smelter emission and dust from mining activities indicate that minerals of the spinel group are one of the common hosts of metal-bearing contaminants. Spinel group minerals typically originate from high temperature processes, but an increasing number of studies indicate that metal-bearing spinel group minerals can also form under ambient Earth surface conditions in surficial soils. In this contribution to honor Donald Sparks, we show that the spinels Zn-bearing magnetite (Zn0.5Fe2.5O4) and minium (Pb3O4) form during low temperature alteration of Pb-bearing silica glass in surficial organic rich soils in proximity to a former Cu-smelter in Timmins, Ontario, Canada. The glass most likely formed during high-temperature processes and has been either emitted by the smelter or wind-blown from waste rock piles to near-by soils. The alteration of the glass by percolating pore solutions has resulted in the formation of large micrometer-size dendritic etch features and in nanometer-size dendritic alteration halos composed of nano-size prismatic crystals of Zn-rich magnetite and spherical nanoparticles of minium. Both spinel-type phases are embedded in an amorphous silica matrix which formed during the alteration of the glass at low temperature. A review on the occurrence of spinel-group minerals in smelter-affected soils or mine tailings indicates that the formation of these minerals under ambient Earth surface conditions is quite common and often results in the sequestration of contaminants such as Cu, Ni, Zn and Sb. The pedogenic spinels often occur as euhedral crystals in nano-size mineral assemblages within alteration features such as dendritic etch patterns, mineral surface coatings and mineralized organic matter. Their well-developed crystal forms indicate that (a) they have not formed during a rapid cooling process in a smelter or refinery which typically creates spherical particulate matter, and (b) they have not been part of particulate matter added via fluvial or Aeolian processes which most commonly yield anhedral morphologies. The formation of nano-size spinel-group minerals in low temperature environmental settings may lead to the long-term storage of metal(loid)s in mineral phases and their transport over vast distances via fluvial, alluvial and Aeolian processes.
Geochemical Transactions. 2019 Mar 13;20(1):1
http://hdl.handle.net/10919/88477
https://doi.org/10.1186/s12932-019-0061-3
The formation of spinel-group minerals in contaminated soils: the sequestration of metal(loid)s by unexpected incidental nanoparticles
oai:vtechworks.lib.vt.edu:10919/1115652022-08-20T07:19:16Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Aruta, Antonio
author
Albanese, Stefano
author
Daniele, Linda
author
Cannatelli, Claudia
author
Buscher, Jamie T.
author
De Vivo, Benedetto
author
Petrik, Attila
author
Cicchella, Domenico
author
Lima, Annamaria
author
2022-01-10
In 2017, a geochemical survey was carried out across the Commune of Santiago, a local administrative unit located at the center of the namesake capital city of Chile, and the concentration of a number of major and trace elements (53 in total) was determined on 121 topsoil samples. Multifractal IDW (MIDW) interpolation method was applied to raw data to generate geochemical baseline maps of 15 potential toxic elements (PTEs); the concentration-area (C-A) plot was applied to MIDW grids to highlight the fractal distribution of geochemical data. Data of PTEs were elaborated to statistically determine local geochemical baselines and to assess the spatial variation of the degree of soil contamination by means of a new method taking into account both the severity of contamination and its complexity. Afterwards, to discriminate the sources of PTEs in soils, a robust Principal Component Analysis (PCA) was applied to data expressed in isometric log-ratio (ilr) coordinates. Based on PCA results, a Sequential Binary Partition (SBP) was also defined and balances were determined to generate contrasts among those elements considered as proxies of specific contamination sources (Urban traffic, productive settlements, etc.). A risk assessment was finally completed to potentially relate contamination sources to their potential effect on public health in the long term. A probabilistic approach, based on Monte Carlo method, was deemed more appropriate to include uncertainty due to spatial variation of geochemical data across the study area. Results showed how the integrated use of multivariate statistics and compositional data analysis gave the authors the chance to both discriminate between main contamination processes characterizing the soil of Santiago and to observe the existence of secondary phenomena that are normally difficult to constrain. Furthermore, it was demonstrated how a probabilistic approach in risk assessment could offer a more reliable view of the complexity of the process considering uncertainty as an integral part of the results.
0269-4042
http://hdl.handle.net/10919/111565
https://doi.org/10.1007/s10653-021-01185-6
35014008
1573-2983
Urban geochemistry
Contamination degree assessment
Multifractal IDW
Compositional data analysis (CoDA)
Proabilistic risk assessment
Monte Carlo method
A new approach to assess the degree of contamination and determine sources and risks related to PTEs in an urban environment: the case study of Santiago (Chile)
oai:vtechworks.lib.vt.edu:10919/1116752022-09-01T07:15:54Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Xu, Xiao-Tao
author
Shao, Long-Yi
author
Eriksson, Kenneth A.
author
Pang, Bo
author
Wang, Shuai
author
Yang, Cheng-Xue
author
Hou, Hai-Hai
author
2022-01
The early Albian Oceanic Anoxic Event 1b (OAE 1b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1b exist. In order to identify terrestrial records of the early Albian OAE 1b and to infer possible driving mechanisms, an integrated multi-proxy study from the late Aptian to Albian in the Fuxin lacustrine basin was conducted, including thick, organic-rich black mudstones, total organic carbon (TOC), organic carbon isotopes (d13Corg), mercury concentration (Hg) and results from pyrolysis analyses (S2, Tmax and HI). Results show three distinct short-term negative d13Corg excursions corresponding with relatively high TOC values, which could be counterparts of the Kilian, Paquier and Leenhardt sub-events of the early Albian OAE 1b. Atmospheric CO2 concentration (pCO2) recovered from C3 plant d13Corg compositions indicates an increasing trend in Unit C during the early Albian, and there are three short-term increases of pCO2 corresponding to the three sub-events of OAE 1b at this time interval. We infer that a trend of increasing pCO2 during the Kilian sub-event in the study area is closely related to volcanism. Continental weathering calculated using chemical weathering indices (CIA, WIP and MIA(O)) show an increasing trend during the OAE 1b interval, likely resulting from warmer and more humid conditions. Mixed sources of terrestrial plants and lacustrine plankton demonstrated by pyrolysis analyses (HI vs. Tmax and S2 vs. TOC), indicate a terrestrial contribution to the organic-rich sediments of the Kilian, Paquier and Leenhardt sub-events of OAE 1b. We suggest that a CO2-forced greenhouse effect during the early Albian might have triggered the relatively warm and humid palaeoclimatic conditions, and intensified chemical weathering that combined to create high nutrient and organic matter levels that were flushed into lakes contributing to eutrophication and anoxia in lacustrine and in contemporaneous oceanic systems. (c) 2021 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
Beijing
101275
http://hdl.handle.net/10919/111675
https://doi.org/10.1016/j.gsf.2021.101275
13
1
Fuxin Basin
Early Albian
Organic carbon isotopes
Ocean Anoxic Event 1b
Terrestrial records
Terrestrial records of the early Albian Ocean Anoxic Event: Evidence from the Fuxin lacustrine basin, NE China
oai:vtechworks.lib.vt.edu:10919/517092020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Hochella, Michael F. Jr.
author
Spencer, Michael G.
author
Jones, Kimberly L.
author
2014-12-02
In the field of environmental nanotechnology, opinions on the novelty of engineered nanomaterials vary; some scientists believe that many engineered nanomaterials are indeed unique, while others are convinced that we are simply fabricating structures already designed in nature. In this article, we present balanced, objective evidence on both sides of the debate. While the idea of novel nanomaterials opens the mind to imagine truly unique structures with architectures unparalleled in nature, the idea that these structures have related analogs in nature has environmental relevance as scientists and engineers aim to design and manufacture more sustainable and environmentally benign nanomaterials.
Hochella, M. F., Spencer, M. G., & Jones, K. L. (2015). Nanotechnology: nature's gift or scientists' brainchild? Environmental Science: Nano, 2(2), 114-119. doi: 10.1039/C4EN00145A
2051-8153
http://hdl.handle.net/10919/51709
http://pubs.rsc.org/en/content/articlelanding/2015/en/c4en00145a
https://doi.org/10.1039/C4EN00145A
Environmental nanotechnology
Engineered nanomaterials
Nanobiogeoscience
Nanotechnology: Nature's Gift or Scientists' Brainchild?
oai:vtechworks.lib.vt.edu:10919/1042512023-11-29T19:09:42Zcom_10919_78629com_10919_78628com_10919_5540com_10919_23829com_10919_5553com_10919_91913com_10919_23198com_10919_24209com_10919_24213com_10919_91912col_10919_78630col_10919_71752col_10919_23830col_10919_91914col_10919_24267col_10919_24334col_10919_91916
00925njm 22002777a 4500
dc
Ceci, Alessandro
author
Muñoz-Ballester, Carmen
author
Tegge, Allison N.
author
Brown, Katherine L.
author
Umans, Robyn A.
author
Michel, F. Marc
author
Patel, Dipankumar
author
Tewari, Bhanu P.
author
Martin, James E.
author
Alcoreza, Oscar Jr.
author
Maynard, Thomas M.
author
Martinez-Martinez, Daniel
author
Bordwine, Paige
author
Bissell, Noelle
author
Friedlander, Michael J.
author
Sontheimer, Harald
author
Finkielstein, Carla V.
author
2021-07-20
Rapid and widespread testing of severe acute respiratory coronavirus 2 (SARS-CoV-2) is essential for an effective public health response aimed at containing and mitigating the coronavirus disease 2019 (COVID-19) pandemic. Successful health policy implementation relies on early identification of infected individuals and extensive contact tracing. However, rural communities, where resources for testing are sparse or simply absent, face distinctive challenges to achieving this success. Accordingly, we report the development of an academic, public land grant University laboratory-based detection assay for the identification of SARS-CoV-2 in samples from various clinical specimens that can be readily deployed in areas where access to testing is limited. The test, which is a quantitative reverse transcription polymerase chain reaction (RT-qPCR)-based procedure, was validated on samples provided by the state laboratory and submitted for FDA Emergency Use Authorization. Our test exhibits comparable sensitivity and exceeds specificity and inclusivity values compared to other molecular assays. Additionally, this test can be re-configured to meet supply chain shortages, modified for scale up demands, and is amenable to several clinical specimens. Test development also involved 3D engineering critical supplies and formulating a stable collection media that allowed samples to be transported for hours over a dispersed rural region without the need for a cold-chain. These two elements that were critical when shortages impacted testing and when personnel needed to reach areas that were geographically isolated from the testing center. Overall, using a robust, easy-to-adapt methodology, we show that an academic laboratory can supplement COVID-19 testing needs and help local health departments assess and manage outbreaks. This additional testing capacity is particularly germane for smaller cities and rural regions that would otherwise be unable to meet the testing demand.
http://hdl.handle.net/10919/104251
https://doi.org/10.1038/s41467-021-24552-4
12
COVID-19
Gene expression profiling
Genomic analysis
Virus testing
Rural areas
Development and implementation of a scalable and versatile test for COVID-19 diagnostics in rural communities
oai:vtechworks.lib.vt.edu:10919/1164392023-10-11T07:13:45Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Khorrami, Mohammad
author
Shirzaei, Manoochehr
author
Ghobadi-Far, Khosro
author
Werth, Susanna
author
Carlson, Grace
author
Zhai, Guang
author
2023-03
Groundwater withdrawal can cause localized and rapid poroelastic subsidence, spatially broad elastic uplift of low amplitude, and changes in the gravity field. Constraining groundwater loss in Mexico City, we analyze data from the Gravity Recovery and Climate Experiment and its follow-on mission (GRACE/FO) and Synthetic Aperture Radar (SAR) Sentinel-1A/B images between 2014 and 2021. GRACE/FO observations yield a groundwater loss of 0.85-3.87 km(3)/yr for a region of similar to 300 x 600 km surrounding Mexico City. Using the high-resolution interferometric SAR data set, we measure >35 cm/yr subsidence within the city and up to 2 cm/yr of uplift in nearby areas. Attributing the long-term subsidence to poroelastic aquifer compaction and the long-term uplift to elastic unloading, we apply respective models informed by local geology, yielding groundwater loss of 0.86-12.57 km(3)/yr. Our results suggest Mexico City aquifers have been depleting at faster rates since 2015, exacerbating the socioeconomic and health impacts of long-term groundwater overdrafts.
0094-8276
e2022GL101962
http://hdl.handle.net/10919/116439
https://doi.org/10.1029/2022GL101962
50
5
1944-8007
poroelastic subsidence
uplift
InSAR
GRACE-derived total water storage
groundwater mass loss
elastic load models
Groundwater Volume Loss in Mexico City Constrained by InSAR and GRACE Observations and Mechanical Models
oai:vtechworks.lib.vt.edu:10919/1088162022-02-23T20:03:33Zcom_10919_5com_10919_25799com_10919_18738com_10919_5539com_10919_24209com_10919_5553col_10919_70873col_10919_23145col_10919_24267
00925njm 22002777a 4500
dc
Clavel, Michael B.
author
Liu, Jheng-Sin
author
Bodnar, Robert J.
author
Hudait, Mantu K.
author
2022-02-08
The indirect nature of silicon (Si) emission currently limits the monolithic integration of photonic circuitry with Si electronics. Approaches to circumvent the optical shortcomings of Si include band structure engineering via alloying (e.g., SixGe1–x–ySny) and/or strain engineering of group IV materials (e.g., Ge). Although these methods enhance emission, many are incapable of realizing practical lasing structures because of poor optical and electrical confinement. Here, we report on strong optoelectronic confinement in a highly tensile-strained (ε) Ge/In0.26Al0.74As heterostructure as determined by X-ray photoemission spectroscopy (XPS). To this end, an ultrathin (∼10 nm) ε-Ge epilayer was directly integrated onto the In0.26Al0.74As stressor using an in situ, dual-chamber molecular beam epitaxy approach. Combining high-resolution X-ray diffraction and Raman spectroscopy, a strain state as high as ε ∼ 1.75% was demonstrated. Moreover, high-resolution transmission electron microscopy confirmed the highly ordered, pseudomorphic nature of the as-grown ε-Ge/In0.26Al0.74As heterostructure. The heterointerfacial electronic structure was likewise probed via XPS, revealing conduction- and valence band offsets (ΔEC and ΔEV) of 1.25 ± 0.1 and 0.56 ± 0.1 eV, respectively. Finally, we compare our empirical results with previously published first-principles calculations investigating the impact of heterointerfacial stoichiometry on the ε-Ge/InxAl1–xAs energy band offset, demonstrating excellent agreement between experimental and theoretical results under an As0.5Ge0.5 interface stoichiometry exhibiting up to two monolayers of heterointerfacial As–Ge diffusion. Taken together, these findings reveal a new route toward the realization of on-Si photonics.
2470-1343
http://hdl.handle.net/10919/108816
https://doi.org/10.1021/acsomega.1c06203
Hudait, Mantu [0000-0002-9789-3081]
2470-1343
0904 Chemical Engineering
0912 Materials Engineering
Mapping the Interfacial Electronic Structure of Strain-Engineered Epitaxial Germanium Grown on InxAl1–xAs Stressors
oai:vtechworks.lib.vt.edu:10919/1177262024-01-30T03:02:46Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Namayandeh, Alireza
author
Borkiewicz, Olaf J.
author
Bompoti, Nefeli M.
author
Watson, Steven K.
author
Kubicki, James D.
author
Chrysochoou, Maria
author
Michel, F. Marc
author
2023-10-19
In natural environments, ferrihydrite (Fh) reacts readily with the contaminant and nutrient oxyanions through surface complexation. While previous experiments showed that the transformation of Fh to Gt and Hm under oxic conditions at 70 °C is controlled by the type and strength of oxyanion surface complexes, the impact of surface loading on this process is only partly understood. Synchrotron scattering methods and chemical analysis were used to develop a kinetic model that describes the impact of oxyanion surface loading on the rate and pathway of Fh transformation by using arsenate (AsO43-) and phosphate (PO43-). Kinetic modeling showed that AsO43- and PO43- adsorption decreased the rate of transformation and favored Hm formation over Gt. Higher surface loadings increasingly inhibited Fh transformation with a greater effect for PO43- compared with AsO43-. This information has implications for understanding the impacts of oxyanions on the transformation of natural Fe to Gt and Hm in environmental systems.
2472-3452
https://hdl.handle.net/10919/117726
https://doi.org/10.1021/acsearthspacechem.3c00232
7
10
Michel, Frederick [0000-0003-2817-980X]
2472-3452
hematite
goethite
arsenate
phosphate
hydration
oriented attachment
dissolution/recrystallization
Effects of Oxyanion Surface Loading on the Rate and Pathway of Ferrihydrite Transformation
oai:vtechworks.lib.vt.edu:10919/1182942024-03-07T12:02:42Zcom_10919_24209com_10919_5553com_10919_110083col_10919_24267col_10919_110084
00925njm 22002777a 4500
dc
Ohenhen, Leonard O.
author
Shirzaei, Manoochehr
author
Ojha, Chandrakanta
author
Sherpa, Sonam F.
author
Nicholls, Robert J.
author
2024-03-06
The sea level along the US coastlines is projected to rise by 0.25–0.3 m by 2050, increasing the probability of more destructive flooding and inundation in major cities. However, these impacts may be exacerbated by coastal subsidence— the sinking of coastal land areas—a factor that is often underrepresented in coastal-management policies and long-term urban planning. In this study, we combine high-resolution vertical land motion (that is, raising or lowering of land) and elevation datasets with projections of sea-level rise to quantify the potential inundated areas in 32 major US coastal cities. Here we show that, even when considering the current coastal-defence structures, further land area of between 1,006 and 1,389 km² is threatened by relative sea-level rise by 2050, posing a threat to a population of 55,000–273,000 people and 31,000–171,000 properties. Our analysis shows that not accounting for spatially variable land subsidence within the cities may lead to inaccurate projections of expected exposure. These potential consequences show the scale of the adaptation challenge, which is not appreciated in most US coastal cities.
https://hdl.handle.net/10919/118294
https://doi.org/10.1038/s41586-024-07038-3
627
Disappearing cities on US coasts
oai:vtechworks.lib.vt.edu:10919/964172023-04-18T18:49:05Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Schwarzenbach, Esther M.
author
Li, J.
author
John, T.
author
Caddick, Mark J.
author
Petroff, Matthew
author
Gill, Benjamin C.
author
2019-04
Subduction zones significantly control the geochemical cycling and elemental transfer between the surficial andinternal reservoirs of the Earth. Amongst the most hydrophile elements sulfur is the fifth most abundant element on Earth. Subduction of oceanic lithosphere transports sulfur together with numerous other elements into Earth’s mantle and releases sulfur-bearing fluids modifying the redox state and the chemical budget of the mantle. Here, we present bulk rock sulfur geochemical data of exhumed mafic and ultramafic slab material to provide new insights into the sulfur cycle within subduction zones. Our data shows that small bodies of detached slab material are subject to metasomatic processes during exhumation (e.g., within a subduction zone channel), where fluids thatare circulating along the plate interface cause sulfur mobilization. Sulfur mobilization is thereby more pronounced within serpentinites compared to mafic rocks. In contrast, large sequences of obducted ophiolitic sections can retain their seafloor alteration signatures, particularly at moderate peak P-T conditions. Furthermore, dehydration-related vein systems in blue schists provide evidence for sulfur transfer within the subducted oceanic crust. These vein systems carry distinct sulfur isotopic signatures that reflect dehydration processes of underlying sequences suggesting a negative sulfur isotope signature of the dehydrating subducting slab. Our data provides new insights into the sulfur transfer between the slab and the mantle wedge, which may eventually control the formation of arc-related melts and porphyry deposits.
http://hdl.handle.net/10919/96417
21
Gill, Benjamin [0000-0001-7402-0811]
Sulfur cycling within subduction zones: Insights from exhumed mafic and ultramafic slab
oai:vtechworks.lib.vt.edu:10919/854072022-02-26T15:58:40Zcom_10919_78629com_10919_78628com_10919_112356com_10919_23261com_10919_5539com_10919_24209com_10919_5553com_10919_23765col_10919_78630col_10919_112358col_10919_24267col_10919_24353
00925njm 22002777a 4500
dc
Yang, Yi
author
Chen, Bo
author
Hower, James C.
author
Schindler, Michael
author
Winkler, Christopher
author
Brandt, Jessica E.
author
Di Giulio, Richard T.
author
Ge, Jianping
author
Liu, Min
author
Fu, Yuhao
author
Zhang, Lijun
author
Chen, Yu-ru
author
Priya, Shashank
author
Hochella, Michael F. Jr.
author
2017-01-12
Coal, as one of the most economic and abundant energy sources, remains the leading fuel for producing electricity worldwide. Yet, burning coal produces more global warming CO2 relative to all other fossil fuels, and it is a major contributor to atmospheric particulate matter known to have a deleterious respiratory and cardiovascular impact in humans, especially in China and India. Here we have discovered that burning coal also produces large quantities of otherwise rare Magneli phases (Ti; x; O2x–1 with 4 ≤ x ≤ 9) from TiO2 minerals naturally present in coal. This provides a new tracer for tracking solid-state emissions worldwide from industrial coal-burning. In its first toxicity testing, we have also shown that nanoscale Magneli phases have potential toxicity pathways that are not photoactive like TiO2 phases, but instead seem to be biologically active without photostimulation. In the future, these phases should be thoroughly tested for their toxicity in the human lung. Solid-state emissions from coal burning remain an environmental concern. Here, the authors have found that TiO2 minerals present in coal are converted into titanium suboxides during burning, and initial biotoxicity screening suggests that further testing is needed to look into human lung consequences.
20411723
http://hdl.handle.net/10919/85407
https://doi.org/10.1038/s41467-017-00276-2
8
28790379
Discovery and ramifications of incidental Magnéli phase generation and release from industrial coal-burning
oai:vtechworks.lib.vt.edu:10919/987442022-02-26T22:22:45Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Sublett, D. Matthew, Jr.
author
Sendula, Eszter
author
Lamadrid, Hector M.
author
Steele-MacInnis, Matthew
author
Spiekermann, Georg
author
Burruss, Robert C.
author
Bodnar, Robert J.
author
2020-03
The Raman spectra of pure N-2, CO2, and CH4 were analyzed over the range 10 to 500 bars and from -160 degrees C to 200 degrees C (N-2), 22 degrees C to 350 degrees C (CO2), and -100 degrees C to 450 degrees C (CH4). At constant temperature, Raman peak position, including the more intense CO2 peak (nu+), decreases (shifts to lower wave number) with increasing pressure for all three gases over the entire pressure and temperature (PT) range studied. At constant pressure, the peak position for CO2 and CH4 increases (shifts to higher wave number) with increasing temperature over the entire PT range studied. In contrast, N-2 first shows an increase in peak position with increasing temperature at constant pressure, followed by a decrease in peak position with increasing temperature. The inflection temperature at which the trend reverses for N-2 is located between 0 degrees C and 50 degrees C at pressures above similar to 50 bars and is pressure dependent. Below similar to 50 bars, the inflection temperature was observed as low as -120 degrees C. The shifts in Raman peak positions with PT are related to relative density changes, which reflect changes in intermolecular attraction and repulsion. A conceptual model relating the Raman spectral properties of N-2, CO2, and CH4 to relative density (volume) changes and attractive and repulsive forces is presented here. Additionally, reduced temperature-dependent densimeters and barometers are presented for each pure component over the respective PT ranges. The Raman spectral behavior of the pure gases as a function of temperature and pressure is assessed to provide a framework for understanding the behavior of each component in multicomponent N-2-CO2-CH4 gas systems in a future study.
0377-0486
http://hdl.handle.net/10919/98744
https://doi.org/10.1002/jrs.5805
51
3
1097-4555
fluids
wave number
attraction
repulsion
Shift in the Raman symmetric stretching band of N-2, CO2, and CH4 as a function of temperature, pressure, and density
oai:vtechworks.lib.vt.edu:10919/819462023-04-18T18:48:28Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Zhang, H.
author
Xiao, S.
author
2017-07-01
http://hdl.handle.net/10919/81946
https://doi.org/10.1127/njgpa/2017/0668
285
Xiao, S [0000-0003-4655-2663]
Three-dimensionally phosphatized meiofaunal bivalved arthropods from the upper Cambrian of western Hunan, South China
oai:vtechworks.lib.vt.edu:10919/1010832020-12-12T08:11:41Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Carlson, Grace
author
Shirzaei, Manoochehr
author
Ojha, Chandrakanta
author
Werth, Susanna
author
2020-09
Large-scale subsidence due to aquifer-overdraft is an ongoing hazard in the San Joaquin Valley. Subsidence continues to cause damage to infrastructure and increases the risk of extensional fissures.Here, we use InSAR-derived vertical land motion (VLM) to model the volumetric strain rate due to groundwater storage change during the 2007-2010 drought in the San Joaquin Valley, Central Valley, California. We then use this volumetric strain rate model to calculate surface tensile stress in order to predict regions that are at the highest risk for hazardous tensile surface fissures. We find a maximum volumetric strain rate of -232 microstrain/yr at a depth of 0 to 200 m in Tulare and Kings County, California. The highest risk of tensile fissure development occurs at the periphery of the largest subsiding zones, particularly in Tulare County and Merced County. Finally, we assume that subsidence is likely due to aquifer pressure change, which is calculated using groundwater level changes observed at 300 wells during this drought. We combine pressure data from selected wells with our volumetric strain maps to estimate the quasi-static bulk modulus, K, a poroelastic parameter applicable when pressure change within the aquifer is inducing volumetric strain. This parameter is reflective of a slow deformation process and is one to two orders of magnitude lower than typical values for the bulk modulus found using seismic velocity data. The results of this study highlight the importance of large-scale, high-resolution VLM measurements in evaluating aquifer system dynamics, hazards associated with overdraft, and in estimating important poroelastic parameters.
2169-9313
e2020JB019980
http://hdl.handle.net/10919/101083
https://doi.org/10.1029/2020JB019980
125
9
33042724
2169-9356
Subsidence-Derived Volumetric Strain Models for Mapping Extensional Fissures and Constraining Rock Mechanical Properties in the San Joaquin Valley, California
oai:vtechworks.lib.vt.edu:10919/1130332023-01-05T08:13:29Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Them, Theodore R.
author
Gill, Benjamin C.
author
Caruthers, Andrew H.
author
Gerhardt, Angela M.
author
Grocke, Darren R.
author
Lyons, Timothy W.
author
Marroquin, Selva M.
author
Nielsen, Sune G.
author
Alexandre, Joao P. Trabucho
author
Owens, Jeremy D.
author
2018-06-26
For this study, we generated thallium (Tl) isotope records from two anoxic basins to track the earliest changes in global bottom water oxygen contents over the Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma) of the Early Jurassic. The T-OAE, like other Mesozoic OAEs, has been interpreted as an expansion of marine oxygen depletion based on indirect methods such as organic-rich facies, carbon isotope excursions, and biological turnover. Our Tl isotope data, however, reveal explicit evidence for earlier global marine deoxygenation of ocean water, some 600 ka before the classically defined T-OAE. This antecedent deoxygenation occurs at the Pliensbachian/Toarcian boundary and is coeval with the onset of initial large igneous province (LIP) volcanism and the initiation of a marine mass extinction. Thallium isotopes are also perturbed during the T-OAE interval, as defined by carbon isotopes, reflecting a second deoxygenation event that coincides with the acme of elevated marine mass extinctions and the main phase of LIP volcanism. This suggests that the duration of widespread anoxic bottom waters was at least 1 million years in duration and spanned early to middle Toarcian time. Thus, the Tl data reveal a more nuanced record of marine oxygen depletion and its links to biological change during a period of climatic warming in Earth’s past and highlight the role of oxygen depletion on past biological evolution.
0027-8424
1803478115 (PII)
http://hdl.handle.net/10919/113033
https://doi.org/10.1073/pnas.1803478115
115
26
Gill, Benjamin [0000-0001-7402-0811]
29891692
1091-6490
Toarcian Oceanic Anoxic Event
Early Jurassic
thallium isotopes
carbon isotope excursion
large igneous province
ORGANIC-MATTER
OCEAN ANOXIA
EVENT
PRESERVATION
SEDIMENTS
STAGE
FRACTIONATION
GEOCHEMISTRY
PERTURBATION
CONSTRAINTS
Thallium isotopes reveal protracted anoxia during the Toarcian (Early Jurassic) associated with volcanism, carbon burial, and mass extinction
oai:vtechworks.lib.vt.edu:10919/984162023-11-29T11:19:34Zcom_10919_98410com_10919_25796com_10919_24209com_10919_5553col_10919_98411col_10919_24267
00925njm 22002777a 4500
dc
Cox, Ronadh
author
Ardhuin, Fabrice
author
Dias, Frederic
author
Autret, Ronan
author
Beisiegel, Nicole
author
Earlie, Claire S.
author
Herterich, James G.
author
Kennedy, Andrew
author
Paris, Raphael
author
Raby, Alison
author
Schmitt, Pal
author
Weiss, Robert
author
2020-02-05
Coastal boulder deposits (CBD), transported by waves at elevations above sea level and substantial distances inland, are markers for marine incursions. Whether they are tsunami or storm deposits can be difficult to determine, but this is of critical importance because of the role that CBD play in coastal hazard analysis. Equations from seminal work by Nott (1997), here referred to as the Nott Approach, are commonly employed to calculate nominal wave heights from boulder masses as a means to discriminate between emplacement mechanisms. Systematic review shows that this approach is based on assumptions that are not securely founded and that direct relationships cannot be established between boulder measurements and wave heights. A test using an unprecedented dataset of boulders moved by storm waves (with associated sea-state data) shows a lack of agreement between calculations and actual wave heights. The equations return unrealistically large heights, many of which greatly exceed sea states occurring during the boulder-moving storms. This underscores the finding that Nott-Approach wave-height calculations are unreliable. The result is general, because although the field data come from one region (the Aran Islands, Ireland), they represent a wide range of boulder masses and topographic settings and present a valid test of hydrodynamic equations. This analysis demonstrates that Nott Approach equations are incapable of distinguishing storm waves from tsunami transport and that wave heights hindcast from boulder masses are not meaningful. Current hydrodynamic understanding does not permit reliable computation of wave height from boulder measurements. A combination of field, numerical, and experimental approaches is required to quantify relationships between wave power and mass transport onshore. Many CBD interpreted as tsunami deposits based on Nott-Approach analysis may in fact have been emplaced during storms and should therefore be re-evaluated. This is especially important for CBD that have been incorporated into long-term coastal risk assessments, which are compromised if the CBD are misinterpreted. CBD dynamics can be better determined from a combination of detailed field measurements, modeling, and experiments. A clearer understanding of emplacement mechanisms will result in more reliable hazard analysis.
4
http://hdl.handle.net/10919/98416
https://doi.org/10.3389/fmars.2020.00004
7
2296-7745
coastal boulder deposits
storm waves
tsunami
hydrodynamic equations
coastal erosion
coastal hazard
coastal geomorphology
wave modeling
Systematic Review Shows That Work Done by Storm Waves Can Be Misinterpreted as Tsunami-Related Because Commonly Used Hydrodynamic Equations Are Flawed
oai:vtechworks.lib.vt.edu:10919/1021142021-01-29T08:16:42Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Nesbitt, Sterling J.
author
Zawiskie, John M.
author
Dawley, Robert M.
author
2020-10-27
Loricatan pseudosuchians (known as "rauisuchians") typically consist of poorly understood fragmentary remains known worldwide from the Middle Triassic to the end of the Triassic Period. Renewed interest and the discovery of more complete specimens recently revolutionized our understanding of the relationships of archosaurs, the origin of Crocodylomorpha, and the paleobiology of these animals. However, there are still few loricatans known from the Middle to early portion of the Late Triassic and the forms that occur during this time are largely known from southern Pangea or Europe. Heptasuchus clarki was the first formally recognized North American "rauisuchian" and was collected from a poorly sampled and disparately fossiliferous sequence of Triassic strata in North America. Exposed along the trend of the Casper Arch flanking the southeastern Big Horn Mountains, the type locality of Heptasuchus clarki occurs within a sequence of red beds above the Alcova Limestone and Crow Mountain formations within the Chugwater Group. The age of the type locality is poorly constrained to the Middle-early Late Triassic and is likely similar to or just older than that of the Popo Agie Formation assemblage from the western portion of Wyoming. The holotype consists of associated cranial elements found in situ, and the referred specimens consist of crania and postcrania. Thus, about 30% of the osteology of the taxon is preserved. All of the pseudosuchian elements collected at the locality appear to belong to Heptasuchus clarki and the taxon is not a chimera as previously hypothesized. Heptasuchus clarki is distinct from all other archosaurs by the presence of large, posteriorly directed flanges on the parabasisphenoid and a distinct, orbit-overhanging postfrontal. Our phylogenetic hypothesis posits a sister-taxon relationship between Heptasuchus clarki and the Ladinian-aged Batrachotomus kupferzellensis from current-day Germany within Loricata. These two taxa share a number of apomorphies from across the skull and their phylogenetic position further supports `rauisuchian' paraphyly. A minimum of three individuals of Heptasuchus are present at the type locality suggesting that a group of individuals died together, similar to other aggregations of loricatans (e.g., Heptasuchus, Batrachotomus, Decuriasuchus, Postosuchus).
2167-8359
e10101
http://hdl.handle.net/10919/102114
https://doi.org/10.7717/peerj.10101
8
33194383
Archosauria
Triassic
Mesozoic
Wyoming
Chugwater Group
Phylogeny
Osteology
Pseudosuchia
The osteology and phylogenetic position of the loricatan (Archosauria: Pseudosuchia) Heptasuchus clarki, from the ?Mid-Upper Triassic, southeastern Big Horn Mountains, Central Wyoming (USA)
oai:vtechworks.lib.vt.edu:10919/1049212023-11-29T19:10:11Zcom_10919_5540com_10919_24209com_10919_5553col_10919_71752col_10919_24267
00925njm 22002777a 4500
dc
Nagurney, Alexandra B.
author
Caddick, Mark J.
author
Pattison, David R.M.
author
Michel, F. Marc
author
2021
Electron back scattered diffraction data of garnet crystals from the Nelson Aureole, British Columbia and the Mosher’s Island formation, Nova Scotia, reveals that 22 garnet crystals are all oriented with one of three crystal directions parallel to the trace of the foliation plane in thin section. Structural models suggest that these relationships are due to preferential garnet nucleation onto muscovite, with the alignment of repeating rows of Al octahedra and Si tetrahedra in each leading to inheritance of garnet orientation from the muscovite. These results highlight that epitaxial nucleation may be a prevalent process by which porphyroblast minerals nucleate during metamorphism and carry implications for the role that non-classic nucleation pathways play in the crystallization of metamorphic minerals, the distribution of porphyroblasts in metamorphic rocks, and, in cases in which nucleation is the rate limiting step for crystallization, the energetics of metamorphic reactions.
http://hdl.handle.net/10919/104921
https://doi.org/10.1038/s41598-021-85525-7
11
Preferred orientations of garnet porphyroblasts reveal previously cryptic templating during nucleation
oai:vtechworks.lib.vt.edu:10919/1039572021-06-23T07:13:05Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Lerner, Allan H.
author
Wallace, Paul J.
author
Shea, Thomas
author
Mourey, Adrien J.
author
Kelly, Peter J.
author
Nadeau, Patricia A.
author
Elias, Tamar
author
Kern, Christoph
author
Clor, Laura E.
author
Gansecki, Cheryl
author
Lee, R. Lopaka
author
Moore, Lowell R.
author
Werner, Cynthia A.
author
2021-06
Kilauea Volcano's 2018 lower East Rift Zone (LERZ) eruption produced exceptionally high lava effusion rates and record-setting SO2 emissions. The eruption involved a diverse range of magmas, including primitive basalts sourced from Kilauea's summit reservoirs. We analyzed LERZ matrix glasses, melt inclusions, and host minerals to identify melt volatile contents and magma storage depths. The LERZ glasses and melt inclusions span nearly the entire compositional range previously recognized at Kilauea. Melt inclusions in Fo(86-89) olivine from the main eruptive vent (fissure 8) underwent 70-170 degrees C cooling during transport in LERZ carrier melts, causing extensive post-entrapment crystallization and sulfide precipitation. Many of these melt inclusions have low sulfur (400-900 ppm) even after correction for sulfide formation. CO2 and H2O vapor saturation pressures indicate shallow melt inclusion trapping depths (1-5 km), consistent with formation within Kilauea's Halema'uma'u and South Caldera reservoirs. Many of these inclusions also have degassed delta S-34 values (1.5 to -0.5%). Collectively, these results indicate that some primitive melts experienced near-surface degassing before being trapped into melt inclusions. We propose that decades-to-centuries of repeated lava lake activity and lava drain-back during eruptions (e.g., 1959 Kilauea Iki) recycled substantial volumes of degassed magma into Kilauea's shallow reservoir system. Degassing and magma recycling from the 2008-2018 Halema'uma'u lava lake likely reduced the volatile contents of LERZ fissure 8 magmas, resulting in lower fountain heights compared to many prior Kilauea eruptions. The eruption's extreme SO2 emissions were due to high lava effusion rates rather than particularly volatile-rich melts.
0258-8900
43
http://hdl.handle.net/10919/103957
https://doi.org/10.1007/s00445-021-01459-y
83
6
1432-0819
Degassing
Melt inclusions
Sulfur budget
delta S-34
Magma recycling
Kilauea Volcano
The petrologic and degassing behavior of sulfur and other magmatic volatiles from the 2018 eruption of Kilauea, Hawai'i: melt concentrations, magma storage depths, and magma recycling
oai:vtechworks.lib.vt.edu:10919/1115732022-08-23T07:13:12Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Flinchum, Brady A.
author
Holbrook, W. Steven
author
Carr, Bradley J.
author
2022-01-10
Fractures in Earth's critical zone influence groundwater flow and storage and promote chemical weathering. Fractured materials are difficult to characterize on large spatial scales because they contain fractures that span a range of sizes, have complex spatial distributions, and are often inaccessible. Therefore, geophysical characterizations of the critical zone depend on the scale of measurements and on the response of the medium to impulses at that scale. Using P-wave velocities collected at two scales, we show that seismic velocities in the fractured bedrock layer of the critical zone are scale-dependent. The smaller-scale velocities, derived from sonic logs with a dominant wavelength of ~0.3 m, show substantial vertical and lateral heterogeneity in the fractured rock, with sonic velocities varying by 2,000 m/s over short lateral distances (~20 m), indicating strong spatial variations in fracture density. In contrast, the larger-scale velocities, derived from seismic refraction surveys with a dominant wavelength of ~50 m, are notably slower than the sonic velocities (a difference of ~3,000 m/s) and lack lateral heterogeneity. We show that this discrepancy is a consequence of contrasting measurement scales between the two methods; in other words, the contrast is not an artifact but rather information-the signature of a fractured medium (weathered/fractured bedrock) when probed at vastly different scales. We explore the sample volumes of each measurement and show that surface refraction velocities provide reliable estimates of critical zone thickness but are relatively insensitive to lateral changes in fracture density at scales of a few tens of meters. At depth, converging refraction and sonic velocities likely indicate the top of unweathered bedrock, indicative of material with similar fracture density across scales.
772185
http://hdl.handle.net/10919/111573
https://doi.org/10.3389/frwa.2021.772185
3
2624-9375
critical zone
seismic refraction
velocities
critical zone architecture
geophysics
sonic velocities
multiple scales
What Do P-Wave Velocities Tell Us About the Critical Zone?
oai:vtechworks.lib.vt.edu:10919/189402023-12-11T11:08:48Zcom_10919_8195com_10919_25799com_10919_24209com_10919_5553col_10919_18629col_10919_24267
00925njm 22002777a 4500
dc
Sleight, Sean C.
author
Wigginton, Nicholas S.
author
Lenski, Richard E.
author
2006-12-05
Background
In order to study the dynamics of evolutionary change, 12 populations of E. coli B were serially propagated for 20,000 generations in minimal glucose medium at constant 37°C. Correlated changes in various other traits have been previously associated with the improvement in competitive fitness in the selective environment. This study examines whether these evolved lines changed in their ability to tolerate the stresses of prolonged freezing and repeated freeze-thaw cycles during adaptation to a benign environment.
Results
All 12 lines that evolved in the benign environment for 20,000 generations are more sensitive to freeze-thaw cycles than their ancestor. The evolved lines have an average mortality rate of 54% per daily cycle, compared to the ancestral rate of 34%. By contrast, there was no significant difference between the evolved lines and their ancestor in mortality during prolonged freezing. There was also some variability among the evolved lines in susceptibility to repeated freeze-thaw cycles. Those lines that had evolved higher competitive fitness in the minimal glucose medium at 37°C also had higher mortality during freeze-thaw cycles. This variability was not associated, however, with differences among lines in DNA repair functionality and mutability.
Conclusion
The consistency of the evolutionary declines in freeze-thaw tolerance, the correlation between fitness in glucose medium at 37°C and mortality during freeze-thaw cycles, and the absence of greater declines in freeze-thaw survival among the hypermutable lines all indicate a trade-off between performance in minimal glucose medium at 37°C and the capacity to tolerate this stress. Analyses of the mutations that enhance fitness at 37°C may shed light on the physiological basis of this trade-off.
BMC Evolutionary Biology. 2006 Dec 05;6(1):104
http://hdl.handle.net/10919/18940
https://doi.org/10.1186/1471-2148-6-104
Increased susceptibility to repeated freeze-thaw cycles in Escherichia coli following long-term evolution in a benign environment
oai:vtechworks.lib.vt.edu:10919/245052020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Mihailova, B.
author
Angel, R. J.
author
Welsch, A. M.
author
Zhao, J.
author
Engel, J.
author
Paulmann, C.
author
Gospodinov, M.
author
Ahsbahs, H.
author
Stosch, R.
author
Guttler, B.
author
Bismayer, U.
author
2008-07-04
We report pressure-induced structural changes in PbSc0.5Ta0.5O3 studied by single-crystal x-ray diffraction and Raman scattering. The appearance of a soft mode, a change in the volume compressibility, broadening of the diffraction peaks, and suppression of the x-ray diffuse scattering show that a phase transition occurs near p(c)similar to 1.9 GPa. The critical pressure is associated with a decoupling of the displacements of the B site and Pb cations in the existing polar nanoregions, leading to the suppression of B-cation off-center shifts and enhancement of the ferroic distortion in the Pb-O system.
Mihailova, B. ; Angel, R. J. ; Welsch, A. -M. ; et al., Jul 4, 2008. “Pressure-induced phase transition in PbSc0.5Ta0.5O3 as a model Pb-based perovksite-type relaxor ferroelectric,” PHYSICAL REVIEW LETTERS 101(1): 017602. DOI: 10.1103/PhysRevLett.101.017602
0031-9007
http://hdl.handle.net/10919/24505
http://link.aps.org/doi/10.1103/PhysRevLett.101.017602
https://doi.org/10.1103/PhysRevLett.101.017602
perovskites
crossover
Physics
Pressure-induced phase transition in PbSc0.5Ta0.5O3 as a model Pb-based perovksite-type relaxor ferroelectric
oai:vtechworks.lib.vt.edu:10919/1051802022-04-15T20:52:20Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Stocker, Michelle R.
author
2019-12-19
A complex pelvic morphology has been discovered in the fossils of one of the largest crocodylians.
2050-084X
53399 (PII)
http://hdl.handle.net/10919/105180
https://doi.org/10.7554/eLife.53399
8
Stocker, Michelle [0000-0002-6473-8691]
31854298
2050-084X
Life Sciences & Biomedicine
Biology
Life Sciences & Biomedicine - Other Topics
EVOLUTION
Crocodylia
Hox
Miocene
evo-devo
evolutionary biology
gigantism
variation
0601 Biochemistry and Cell Biology
Morphology: Too hip for two sacral vertebrae
oai:vtechworks.lib.vt.edu:10919/738422020-10-22T03:25:32Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Glesener, G.
author
2016-12-12
In 2015 the Virginia Tech Department of Geosciences took a leading role in increasing the level of support for Geoscience instructors by investing in the development of the Geosciences Modeling and Educational Demonstrations Laboratory Curriculum Materials Center (MEDL-CMC). The MEDL-CMC is an innovative curriculum materials center designed to foster new collaborative teaching and learning environments by providing hands-on physical models combined with education technology for instructors and outreach coordinators. The mission of the MEDL-CMC is to provide advanced curriculum material resources for the purpose of increasing and sustaining high impact instructional capacity in STEM education for both formal and informal learning environments. This presentation describes the development methods being used to implement the MEDL-CMC. Major development methods include: (1) adopting a project management system to support collaborations with stakeholders, (2) using a diversified funding approach to achieve financial sustainability and the ability to evolve with the educational needs of the community, and (3) establishing a broad collection of systems-based physical analog models and data collection tools to support integrated sciences such as the geosciences. Discussion will focus on how these methods are used for achieving organizational capacity in the MEDL-CMC and on their intended role in reducing instructor workload in planning both classroom activities and research grant broader impacts.
http://hdl.handle.net/10919/73842
Development of the Virginia Tech Department of Geosciences MEDL-CMC
oai:vtechworks.lib.vt.edu:10919/976202021-10-08T16:43:39Zcom_10919_8195com_10919_25799com_10919_24209com_10919_5553col_10919_78882col_10919_24267
00925njm 22002777a 4500
dc
Ross, Nancy L.
author
Detrie, Therese A.
author
Liu, Zhenxian
author
2020-03-31
High-pressure Raman and infrared spectra of a natural sample of prehnite, with a chemical composition of Ca<sub>2</sub>(Al<sub>0.74</sub>,Fe<sub>0.26</sub>)<sub>2</sub>Si<sub>3</sub>O<sub>10</sub>(OH)<sub>2</sub>, are presented. Analyses of the spectra indicate that prehnite undergoes a reversible structural change between 6 and 8 GPa that is most likely associated with a subtle alteration in the orientation and/or deformation of the polyhedra comprising the framework of the structure. At pressures in excess of ~11 GPa, the high-pressure spectra indicate that prehnite undergoes a reversible phase transition involving the collapse of the framework structure.
Ross, N.L.; Detrie, T.A.; Liu, Z. High-Pressure Raman and Infrared Spectroscopic Study of Prehnite. Minerals 2020, 10, 312.
http://hdl.handle.net/10919/97620
https://doi.org/10.3390/min10040312
prehnite
infrared spectroscopy
Raman spectroscopy
high pressure
phase transition
High-Pressure Raman and Infrared Spectroscopic Study of Prehnite
oai:vtechworks.lib.vt.edu:10919/1030242023-04-28T19:01:47Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Bland, Michael T.
author
Raymond, Carol A.
author
Schenk, Paul M.
author
Fu, Roger R.
author
Kneissl, Thomas
author
Pasckert, Jan Hendrik
author
Hiesinger, Harry
author
Preusker, Frank
author
Park, Ryan S.
author
Marchi, Simone
author
King, Scott D.
author
Castillo-Rogez, Julie C.
author
Russell, Christopher T.
author
2016-07-01
Before NASA's Dawn mission, the dwarf planet Ceres was widely believed to contain a substantial ice-rich layer below its rocky surface. The existence of such a layer has significant implications for Ceres's formation, evolution, and astrobiological potential. Ceres is warmer than icy worlds in the outer Solar System and, if its shallow subsurface is ice-rich, large impact craters are expected to be erased by viscous flow on short geologic timescales. Here we use digital terrain models derived from Dawn Framing Camera images to show that most of Ceres's largest craters are several kilometres deep, and are therefore inconsistent with the existence of an ice-rich subsurface. We further show from numerical simulations that the absence of viscous relaxation over billion-year timescales implies a subsurface viscosity that is at least one thousand times greater than that of pure water ice. We conclude that Ceres's shallow subsurface is no more than 30% to 40% ice by volume, with a mixture of rock, salts and/or clathrates accounting for the other 60% to 70%. However, several anomalously shallow craters are consistent with limited viscous relaxation and may indicate spatial variations in subsurface ice content.
1752-0894
http://hdl.handle.net/10919/103024
https://doi.org/10.1038/NGEO2743
9
7
King, Scott [0000-0002-9564-5164]
1752-0908
Physical Sciences
Geosciences, Multidisciplinary
Geology
WATER ICE
TOPOGRAPHY
EVOLUTION
DIFFERENTIATION
DEFORMATION
RELAXATION
SATELLITES
MIXTURES
RHEOLOGY
GANYMEDE
Meteorology & Atmospheric Sciences
Composition and structure of the shallow subsurface of Ceres revealed by crater morphology
oai:vtechworks.lib.vt.edu:10919/1142292023-03-31T07:12:26Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Belkin, Harvey E.
author
De Vivo, Benedetto
author
2023-01-06
Authigenic epidote supergroups are an abundant accessory mineral in the calcium-aluminum silicate and thermometamorphic hydrothermal zones of the Campi Flegrei (Phlegraean Fields) geothermal field located west of Naples, Italy. Geothermal exploration for high-enthalpy fluid produced drill core and cuttings to similar to 3 km depth in the Mofete (MF1, MF2, MF5) and San Vito (SV1, SV3) wells, where measured down-hole temperatures of epidote-bearing samples range from 270-350 degrees C and from 285-390 degrees C for the Mofete and San Vito areas, respectively. Two epidote group (epidote, clinozoisite), some rare earth element (REE)-bearing, and two allanite group (allanite-(Ce), ferriallanite-(Ce)) minerals were identified by electron microprobe. The allanite group is light rare earth element (LREE, La-Gd) enriched, Ce dominant, with REE + Y that varies from 30.59 wt %-14.32 wt %. Complex compositional variation such as oscillatory, sector, and complex (mixed) zoning is a ubiquitous feature observed in the epidote group, which occurs as veins, in vugs, as various size masses, and as isolated single crystals. Compositional zoning is caused by variable Fe <-> Al3+ substitution and XFe [(Fe3+) / (Fe3++Al)] ranges from 0.06-0.33 (Fe3+ = 0.185-0.967 apfu). X-Fe tends to decrease with increasing temperature in the Mofete wells, but its distribution is more complex in the San Vito wells, which records recent fault displacement. The variety and complexity of the epidote supergroup zoning suggest rapid fluid composition and/or intensive parameter fluctuations in the local hydrothermal system.
http://hdl.handle.net/10919/114229
https://doi.org/10.5194/ejm-35-25-2023
35
1
1617-4011
2-14 drill hole
al-fe epidote
campi-flegrei
hydrothermal epidote
volcanic system
rocks
fluid
state
nomenclature
ignimbrites
Compositional variation and zoning of epidote supergroup minerals in the Campi Flegrei geothermal field, Naples, Italy
oai:vtechworks.lib.vt.edu:10919/1180972024-02-22T08:13:47Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Tiampo, K.
author
Woods, C.
author
Huang, L.
author
Sharma, P.
author
Chen, Z.
author
Kar, B.
author
Bausch, D.
author
Simmons, C.
author
Estrada, R.
author
Willis, Michael J.
author
Glasscoe, M.
author
2021-01-01
The rising number of flooding events combined with increased urbanization is contributing to significant economic losses due to damages to structures and infrastructures. Here we present a method for producing all weather maps of flood inundation using a combination of synthetic aperture radar (SAR) remote sensing data and machine learning methods that can be used to provide information on the evolution of flood hazards to DisasterAware©, a global alerting system, that is used to disseminate flood risk information to stakeholders across the globe. While these efforts are still in development, a case study is presented for the major flood event associated with Hurricane Harvey and associated floods that impacted Houston, TX in August of 2017.
9781665403696
https://hdl.handle.net/10919/118097
https://doi.org/10.1109/IGARSS47720.2021.9553601
2021-July
Synthetic aperture radar
Flood characterization
Flood inundation
Machine learning
Geospatial data fusion
A Machine Learning Approach to Flood Depth and Extent Detection Using Sentinel 1A/B Synthetic Aperture Radar
oai:vtechworks.lib.vt.edu:10919/1145142023-04-15T07:12:21Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Troia, Gabrielle
author
Stamps, D. Sarah
author
Lotspeich, R. Russell
author
Duda, James
author
McCoy, Kurt J.
author
Moore, William
author
Hensel, Philippe
author
Hippenstiel, Ryan
author
McKenna, Thomas
author
Andreasen, David
author
Geoghegan, Charles
author
Ulizio, Thomas P.
author
Kronebusch, Madeline
author
Carr, Joel
author
Walters, David
author
Winn, Neil
author
2022-12
The Chesapeake Bay is a region along the eastern coast of the United States where sea-level rise is confounded with poorly resolved rates of land subsidence, thus new constraints on vertical land motions (VLM) in the region are warranted. In this paper, we provide a description of two campaign-style Global Positioning System (GPS) datasets, explain the methods used in data collection and validation, and present the experiment designed to quantify a new baseline of VLM in the Chesapeake Bay region of eastern North America. Data from GPS campaigns in 2019 and 2020 are presented as ASCII RINEX2.11 files and logsheets for each observation from the campaigns. Data were quality checked using the open-source program TEQC, resulting in average multipath 1 and 2 values of 0.68 and 0.57, respectively. All data are archived and publicly available for open access at the geodesy facility UNAVCO to abide by Findable, Accessible, Interoperable, Reusable (FAIR) data principles.
744
http://hdl.handle.net/10919/114514
https://doi.org/10.1038/s41597-022-01864-8
9
1
36460674
2052-4463
Atlantic coast
GPS data from 2019 and 2020 campaigns in the Chesapeake Bay region towards quantifying vertical land motions
oai:vtechworks.lib.vt.edu:10919/1142302023-03-31T07:12:27Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Guo, Zhen
author
Chapman, Martin C.
author
2023-01-05
We investigated the regional attenuation and site responses in the Sichuan Basin and adjacent Songpan-Ganze terrane of the Tibetan Plateau using seismic data recorded at 41 stations from regional earthquakes occurring between January 2009 and October 2020. Fourier amplitude spectra of Lg waves were computed and binned into 18 frequency bins with center frequencies ranging from 0.1 Hz to 20.4 Hz. The quality factor is estimated as Q (f) = 313f (0.74) for the Sichuan Basin and Q (f) = 568f (0.34) for the Songpan-Ganze terrane, reflecting significant differences in the crustal structure beneath these two regions. Relative to the Songpan-Ganze terrane, site responses in the Sichuan Basin are characterized by strong amplification effects at frequencies lower than 6 Hz and obvious attenuation at higher frequencies (> 10 Hz). kappa(0) of stations in the Sichuan Basin show clearly geographical dependence with an average value of 0.045 s, whereas stations in the Songpan-Ganze terrane generally have smaller kappa(0) values with an average value of 0.028 s. In particular, site response and kappa(0) of stations in the Sichuan Basin are found to be dependent on the geographically variable thickness of the sedimentary deposits (sediment thickness). These units are comprised of sedimentary rock and semi-consolidated sediments, with a maximum thickness reaching approximately 10 km. Site response terms in the Sichuan Basin derived from the Lg Fourier spectra exhibit consistent patterns versus sediment thickness as frequency increases. We developed site response models as functions of sediment thickness for stations in the Sichuan Basin. The site response model derived from Lg site terms is consistent with that based on site response terms from coda amplitude spectra and horizontal to vertical (H/V) spectral ratios. The models were then incorporated in the stochastic method of ground motion predictions in the Sichuan Basin for six earthquakes occurring between October 2020 and June 2022. Residual analysis suggests that incorporating the site response models as functions of sediment thickness can improve the ground motion prediction model for the Sichuan Basin from moderate earthquakes.
1016096
http://hdl.handle.net/10919/114230
https://doi.org/10.3389/feart.2022.1016096
10
2296-6463
ground motion prediction
site response
sediment thickness
Sichuan Basin
attenuation
A study of site response in the Longmen Shan and adjacent regions and site response models for the Sichuan Basin
oai:vtechworks.lib.vt.edu:10919/967622020-10-22T03:35:55Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Hoffman, Devin K.
author
Edwards, Hunter R.
author
Barrett, Paul M.
author
Nesbitt, Sterling J.
author
2019-11-05
Following the Permo-Triassic mass extinction, Archosauriformes-the clade that includes crocodylians, birds, and their extinct relatives outside crown Archosauria-rapidly diversified into many distinct lineages, became distributed globally, and, by the Late Triassic, filled a wide array of resource zones. Current scenarios of archosauriform evolution are ambiguous with respect to whether their taxonomic diversification in the Early-Middle Triassic coincided with the initial evolution of dietary specializations that were present by the Late Triassic or if their ecological disparity arose sometime after lineage diversification. Late Triassic archosauriform dietary specialization is recorded by morphological divergence from the plesiomorphic archosauriform tooth condition (laterally-compressed crowns with serrated carinae and a generally triangular lateral profile). Unfortunately, the roots of this diversification are poorly documented, with few known Early-Middle Triassic tooth assemblages, limiting characterizations of morphological diversity during this critical, early period in archosaur evolution. Recent fieldwork (2007-2017) in the Middle Triassic Manda Beds of the Ruhuhu Basin, Tanzania, recovered a tooth assemblage that provides a window into this poorly sampled interval. To investigate the taxonomic composition of that collection, we built a dataset of continuous quantitative and discrete morphological characters based on in situ teeth of known taxonomic status (e.g., Nundasuchus, Parringtonia: N = 65) and a sample of isolated teeth (N = 31). Using crown heights from known taxa to predict tooth base ratio (= base length/width), we created a quantitative morphospace for the tooth assemblage. The majority of isolated, unassigned teeth fall within a region of morphospace shared by several taxa from the Manda Beds (e.g., Nundasuchus, Parringtonia); two isolated teeth fall exclusively within a "Pallisteria" morphospace. A non-metric multidimensional scaling ordination (N = 67) of 11 binary characters reduced overlap between species. The majority of the isolated teeth from the Manda assemblage fall within the Nundasuchus morphospace. This indicates these teeth are plesiomorphic for archosauriforms as Nundasuchus exhibits the predicted plesiomorphic condition of archosauriform teeth. Our model shows that the conservative tooth morphologies of archosauriforms can be differentiated and assigned to species and/or genus, rendering the model useful for identifying isolated teeth. The large overlap in tooth shape among the species present and their overall similarity indicates that dietary specialization lagged behind species diversification in archosauriforms from the Manda Beds, a pattern predicted by Simpson's "adaptive zones" model. Although applied to a single geographic region, our methods offer a promising means to reconstruct ecological radiations and are readily transferable across a broad range of vertebrate taxa throughout Earth history.
2167-8359
e7970
http://hdl.handle.net/10919/96762
https://doi.org/10.7717/peerj.7970
7
31720109
Macroevolution
Archosauria
Diversification
Vertebrate paleontology
Morphospace
Adaptive zones
Reconstructing the archosaur radiation using a Middle Triassic archosauriform tooth assemblage from Tanzania
oai:vtechworks.lib.vt.edu:10919/933932020-10-22T03:36:31Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Fall, Andras
author
Bodnar, Robert J.
author
2018-12
Fluid inclusions in clearly defined fluid inclusion assemblages (FIAs) from various geologic environments were examined to assess the uncertainty associated with determining the temperature of a fluid event based on fluid inclusion homogenization temperatures (T-h). A fluid event is defined as a physical or chemical process such as the healing of a microfracture or the formation of a growth zone in a crystal that occurs in the presence of a fluid phase and results in trapping of fluid inclusions to form an FIA. Examination of data from a large number of fluid events collected within a rigorous temporal and spatial (paragenetic) framework forms the basis for developing a complete fluid pressure-temperature-composition (PTX) history. The range in homogenization temperatures of fluid inclusions within well-constrained FIAs was determined, and the minimum (smallest) range in T-h, the median range in T-h, and the first quartile (Q1 at 25%) and third quartile (Q3 at 75%) of the median T-h ranges were calculated for different fluid environments, including the following: 1. Low-permeability sedimentary environments: 49 out of 144 FIAs show a range in T(h )of <= 1 degrees C; the median range = 2 degrees C (from Q1 = 1 degrees C to Q3 = 3.7 degrees C). 2. Mississippi Valley-type deposits: 11 out of 137 FIAs show a range in T(h )of <= 1 degrees C; the median range = 4.1 degrees C (from Q1 = 2.3 degrees C to Q3 = 8.3 degrees C). 3. Epithermal deposits: 102 out of 923 FIAs show a range in T(h )of <= 1 degrees C; the median range = 9 degrees C (from Q1 = 3.8 degrees C to Q3 = 19 degrees C). 4. Porphyry-type deposits: 24 out of 271 FIAs show a range in T(h )of <= 1 degrees C; the median range = 15 degrees C (from Q1 = 8 degrees C to Q3 = 30 degrees C). 5. Orogenic Au deposits: 21 out of 231 FIAs show a range in T(h )of <= 1 degrees C; the median range = 8.7 degrees C (from Q1 = 4 degrees C to Q3 = 20 degrees C). While all environments show some FIAs in which all the fluid inclusions homogenize at essentially the same temperature (range = <= 1 degrees C), we propose that the median range in T-h reported here represents a reasonable and achievable constraint on the uncertainty associated with the temperature of a fluid event in the environments examined. In summary, the temperature of a fluid event, as represented by the range in T-h of the fluid inclusions within an individual FIA, can be constrained to better than 15 degrees C in all environments examined, and in Mississippi Valley-type and low-permeability (deep) sedimentary basin environments, the range in T-h can be constrained to better than 2 degrees C. The processes that produce variability in T-h of fluid inclusions within an FIA are many and include natural variations in temperature, pressure, or fluid composition during trapping of the FIA, trapping of immiscible fluids, various forms of reequilibration in nature such as necking, stretching, and leakage, and modification of the inclusions during sample preparation and data collection. If the range in homogenization temperature for an individual FIA is found to be greater than the median range determined here for that environment, then assessment of the cause of the variability might provide useful information concerning the trapping and post-trapping history of the sample.
0361-0128
http://hdl.handle.net/10919/93393
https://doi.org/10.5382/econgeo.2018.4614
113
8
1554-0774
How Precisely Can the Temperature of a Fluid Event be Constrained Using Fluid Inclusions?
oai:vtechworks.lib.vt.edu:10919/190782020-11-10T15:27:27Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Read, James Fredrick
author
Eriksson, Kenneth A.
author
2012-12-04
This chapter provides an overview of the Paleozoic sedimentary successions of the Virginia Valley and Ridge and Plateau Provinces of the central Appalachians. It describes the units within a sequence stratigraphic framework, discusses depositional systems recorded by the strata, and evaluates tectonic, eustatic and paleoclimatic controls.
http://hdl.handle.net/10919/19078
geology
Paleozoic Era
Valley and Ridge
Plateau
sedimentology
physical geography
sequence stratigraphy
depositional systems
controls on sedimentation
Appalachian Valley and Ridge and Plateau
Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau
oai:vtechworks.lib.vt.edu:10919/496552020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Sitepu, H.
author
2009-12
Preferred orientation or texture is a common feature of experimental powder patterns. The mathematics of two commonly used models for preferred orientation-the March-Dollase and the generalized spherical-harmonic models-is reviewed. Both models were applied individually to neutron powder data from uniaxially pressed molybdite (MoO3) and calcite (CaCO3) powders in Rietveld analyses, as well as the as-received powders. The structural refinement results are compared to single-crystal structures. The results indicate that reasonable refinement of crystal structures can be obtained using either the March model or generalized spherical-harmonic description. However, the generalized spherical-harmonic description provided better Rietveld fits than the March model for the molybdite and calcite. Therefore, the generalized spherical-harmonic description is recommended for correction of preferred orientation in neutron diffraction analysis for both crystal structure refinement and phase composition analysis. Subsequently, the generalized spherical-harmonic description is extended to crystal structure refinement of annealed and the aged polycrystalline Ni-rich Ni50.7Ti49.30 shape memory alloys. (C) 2009 International Centre for Diffraction Data. [DOI: 10.1154/1.3257906]
Sitepu, H., "Texture and structural refinement using neutron diffraction data from molybdite (MoO3) and calcite (CaCO3) powders and a Ni-rich Ni50.7Ti49.30 alloy," Powder Diffr., Vol. 24(4), 2009. DOI: 10.1154/1.3257906
0885-7156
http://hdl.handle.net/10919/49655
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8491214&fulltextType=RA&fileId=S0885715600001767
https://doi.org/10.1154/1.3257906
preferred orientation
texture
neutron powder diffraction
march model
generalized spherical harmonics
molybdite
calcite
ti50.70ni49.30
shape memory alloy
shape-memory alloy
preferred orientation
rietveld refinement
x-ray
crystal-structure
phase
model
distributions
intensities
density
materials science, characterization & testing
Texture and structural refinement using neutron diffraction data from molybdite (MoO3) and calcite (CaCO3) powders and a Ni-rich Ni50.7Ti49.30 alloy
oai:vtechworks.lib.vt.edu:10919/750172024-03-13T14:09:39Zcom_10919_5com_10919_25799com_10919_24209com_10919_5553col_10919_70873col_10919_24267
00925njm 22002777a 4500
dc
Shen, B.
author
Dong, L.
author
Xiao, S.
author
Lang, X.
author
Huang, K.
author
Peng, Y.
author
Zhou, C.
author
Ke, S.
author
Liu, P.
author
2016-01-07
Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (∼2,500-750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end.
http://hdl.handle.net/10919/75017
https://doi.org/10.1038/ncomms10317
7
2041-1723
Carbonates
Fossils
Magnesium
Methane
Molar
Oxidation-Reduction
Sulfates
Sulfides
Sulfur Isotopes
Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans.
oai:vtechworks.lib.vt.edu:10919/862712020-10-22T03:26:46Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Higman, Bretwood
author
Shugar, Dan H.
author
Stark, Colin P.
author
Ekstrom, Goran
author
Koppes, Michele N.
author
Lynett, Patrick
author
Dufresne, Anja
author
Haeussler, Peter J.
author
Geertsema, Marten
author
Gulick, Sean
author
Mattox, Andrew
author
Venditti, Jeremy G.
author
Walton, Maureen A. L.
author
McCall, Naoma
author
Mckittrick, Erin
author
MacInnes, Breanyn
author
Bilderback, Eric L.
author
Tang, Hui
author
Willis, Michael J.
author
Richmond, Bruce
author
Reece, Robert S.
author
Larsen, Chris
author
Olson, Bjorn
author
Capra, James
author
Ayca, Aykut
author
Bloom, Colin
author
Williams, Haley
author
Bonno, Doug
author
Weiss, Robert
author
Keen, Adam
author
Skanavis, Vassilios
author
Loso, Michael
author
2018-09-06
Glacial retreat in recent decades has exposed unstable slopes and allowed deep water to extend beneath some of those slopes. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever documented worldwide. Precursory deformation began decades before failure, and the event left a distinct sedimentary record, showing that geologic evidence can help understand past occurrences of similar events, and might provide forewarning. The event was detected within hours through automated seismological techniques, which also estimated the mass and direction of the slide - all of which were later confirmed by remote sensing. Our field observations provide a benchmark for modeling landslide and tsunami hazards. Inverse and forward modeling can provide the framework of a detailed understanding of the geologic and hazards implications of similar events. Our results call attention to an indirect effect of climate change that is increasing the frequency and magnitude of natural hazards near glaciated mountains.
2045-2322
12993
http://hdl.handle.net/10919/86271
https://doi.org/10.1038/s41598-018-30475-w
8
30190595
bay
mountains
deposits
islands
flood
The 2015 landslide and tsunami in Taan Fiord, Alaska
oai:vtechworks.lib.vt.edu:10919/253072020-10-29T05:01:47Zcom_10919_24209com_10919_5553col_10919_24267
00925njm 22002777a 4500
dc
Snoke, J. A.
author
Sambridge, M.
author
2002-05
[1] In their study of upper mantle structure beneath the Parana Basin of SE Brazil, Snoke and James [1997] concluded, on the basis of a linearized least squares inversion (LLSI) of surface wave dispersion data, that a strong (5% contrast) low-velocity zone (LVZ) beginning at a depth less than 150 km was not required to fit the data. They were unable to establish a quantitative estimate, however, on the maximum depth at which such a LVZ could be resolved by their data. Sambridge [1999a, 1999b] has introduced the Neighbourhood Algorithm (NA), a direct search method for nonlinear inversion which can be tuned to extract information from an ensemble of models in addition to finding a single best fit model. Applying NA to the Brazilian dispersion data quantifies the statistics of the ensemble of models classified as "acceptable'' based on a data misfit criterion and a smoothness constraint. The NA best fit model is not significantly different from the LLSI best fit model, but the analysis of the ensemble of models provides new insights regarding how well constrained the model is. Synthetics runs show that for this data set, our modeling procedures could resolve a strong LVZ that began at a depth of 120 km but could not rule out such an LVZ beginning at a depth of 180 km.
Snoke, J. A., and M. Sambridge, Constraints on the S wave velocity structure in a continental shield from surface wave data: Comparing linearized least squares inversion and the direct search Neighbourhood Algorithm, J. Geophys. Res., 107(B5), doi:10.1029/2001JB000498, 2002.
0148-0227
http://hdl.handle.net/10919/25307
http://onlinelibrary.wiley.com/doi/10.1029/2001JB000498/pdf
https://doi.org/10.1029/2001jb000498
direct search methods for nonlinear inversion
surface waves
continental lithosphere-asthenosphere rheology
neighbourhood algorithm
neighborhood algorithm
south-america
geophysical inversion
africa
Constraints on the S wave velocity structure in a continental shield from surface wave data: Comparing linearized least squares inversion and the direct search Neighbourhood Algorithm
marc///col_10919_24267/100