Browsing by Author "Zhou, Chuanming"
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- Cracking the superheavy pyrite enigma: possible roles of volatile organosulfur compound emissionLang, Xianguo; Zhao, Zhouqiao; Ma, Haoran; Huang, Kangjun; Li, Songzhuo; Zhou, Chuanming; Xiao, Shuhai; Peng, Yongbo; Liu, Yonggang; Tang, Wenbo; Shen, Bing (2021-10)The global deposition of superheavy pyrite (pyrite isotopically heavier than coeval seawater sulfate in the Neoproterozoic Era and particularly in the Cryogenian Period) defies explanation using the canonical marine sulfur cycle system. Here we report petrographic and sulfur isotopic data (delta S-34(py)) of superheavy pyrite from the Cryogenian Datangpo Formation (660-650 Ma) in South China. Our data indicate a syndepositional/early diagenetic origin of the Datangpo superheavy pyrite, with S-34-enriched H2S supplied from sulfidic (H2S rich) seawater. Instructed by a novel sulfur-cycling model, we propose that the emission of S-34-depleted volatile organosulfur compounds (VOSC) that were generated via sulfide methylation may have contributed to the formation of S-34-enriched sulfidic seawater and superheavy pyrite. The global emission of VOSC may be attributed to enhanced organic matter production after the Sturtian glaciation in the context of widespread sulfidic conditions. These findings demonstrate that VOSC cycling is an important component of the sulfur cycle in Proterozoic oceans.
- Cryptic terrestrial fungus-like fossils of the early Ediacaran PeriodGan, Tian; Luo, Taiyi; Pang, Ke; Zhou, Chuanming; Zhou, Guanghong; Wan, Bin; Li, Gang; Yi, Quiru; Czaja, Andrew D.; Xiao, Shuhai (Nature Research, 2021)The colonization of land by fungi had a significant impact on the terrestrial ecosystem and biogeochemical cycles on Earth surface systems. Although fungi may have diverged ~1500–900 million years ago (Ma) or even as early as 2400 Ma, it is uncertain when fungi first colonized the land. Here we report pyritized fungus-like microfossils preserved in the basal Ediacaran Doushantuo Formation (~635 Ma) in South China. These micro-organisms colonized and were preserved in cryptic karstic cavities formed via meteoric water dissolution related to deglacial isostatic rebound after the terminal Cryogenian snowball Earth event. They are interpreted as eukaryotes and probable fungi, thus providing direct fossil evidence for the colonization of land by fungi and offering a key constraint on fungal terrestrialization.
- Deposition or diagenesis? Probing the Ediacaran Shuram excursion in South China by SIMSCui, Huan; Kitajima, Kouki; Orland, Ian J.; Xiao, Shuhai; Baele, Jean-Marc; Kaufman, Alan J.; Denny, Adam; Zhou, Chuanming; Spicuzza, Michael J.; Fournelle, John H.; Valley, John W. (Elsevier, 2021-11)The Ediacaran Period (ca. 635–541 Ma) witnessed the earliest paleontological evidence for macroscopic animals (i.e., Ediacara biota) and geochemical observations of the largest carbon cycle anomaly in Earth history (i.e., Shuram Excursion, SE). Numerous hypotheses have been proposed for the origins of the SE, ranging from primary seawater anomaly to syn- or post-depositional diagenesis. Despite intensive geochemical and theoretical work published in the past decade, empirical evidence that is strictly based on fundamental petrographic results at the micrometer scale is still limited. To evaluate depositional compositions and diagenetic effects on samples from the SE, we investigated the EN3 interval in the Doushantuo Formation of South China via integrated cathodoluminescence (CL), secondary ion mass spectrometry (SIMS), and scanning electron microscope (SEM). Detailed petrographic observations reveal that the EN3 limestone is dominated by calcite microspar, with minor but variable amounts of disseminated zoned dolomite crystals. The former likely formed via neomorphism of depositional micrite, while the latter was the result of progressive post-depositional dolomitization. The mean values of paired SIMS δ13Ccalcite and δ13Cdolomite compositions are indistinguishable in each sample and consistent with published micro-drilled bulk-powder δ13C values, which we interpret to represent depositional “background” signals of seawater dissolved inorganic carbon (DIC). We also observed μm-scale variability of SIMS δ13C data that may reflect a variable diagenetic overprint after deposition. Our integrated petrographic and geochemical results are consistent with a depositional origin of the SE and provide little evidence for the hypothesized isotope alteration by meteoric and mixing-zone diagenesis or late burial diagenesis. In light of this study, we propose that the SE indeed represents a marine carbon cycle anomaly that bears a close temporal link to the Ediacaran surface environment.
- The Ediacaran frondose fossil Arborea from the Shibantan limestone of South ChinaWang, Xiaopeng; Pang, Ke; Chen, Zhe; Wan, Bin; Xiao, Shuhai; Zhou, Chuanming; Yuan, Xunlai (2020-07-20)Bituminous limestone of the Ediacaran Shibantan Member of the Dengying Formation (551-539 Ma) in the Yangtze Gorges area contains a rare carbonate-hosted Ediacara-type macrofossil assemblage. This assemblage is dominated by the tubular fossil Wutubus Chen et al., 2014 and discoidal fossils, e.g.,Hiemalora Fedonkin, 1982 and Aspidella Billings, 1872, but frondose organisms such as Charnia Ford, 1958, Rangea Gurich, 1929, and Arborea Glaessner and Wade, 1966 are also present. Herein, we report four species of Arborea from the Shibantan assemblage, including the type species Arborea arborea (Glaessner in Glaessner and Daily, 1959) Glaessner and Wade, 1966, Arborea denticulata new species, and two unnamed species, Arboreasp. A and Arboreasp. B. Arborea arboreais the most abundant frond in the Shibantan assemblage. Arborea denticulatan. sp. resembles Arborea arborea in general morphology but differs in its fewer primary branches and lower length/width ratio of primary branches. Arboreasp. A and Arboreasp. B are fronds with a Hiemalora-type basal attachment. Sealing by microbial mats and authigenic cementation may have played an important role in the preservation of Arborea in the Shibantan assemblage. The Shibantan material of Arborea extends the stratigraphic, ecological, and taphonomic ranges of this genus. UUID: http://zoobank.org/554f21da-5f09-4891-9deb-cbc00c41e5f1
- Late Ediacaran trackways produced by bilaterian animals with paired appendagesChen, Zhe; Chen, Xiang; Zhou, Chuanming; Yuan, Xunlai; Xiao, Shuhai (AAAS, 2018-06-06)Ediacaran trace fossils provide key paleontological evidence for the evolution of early animals and their behaviors. Thus far, however, this fossil record has been limited to simple surface trails and relatively shallow burrows. We report possible trackways, preserved in association with burrows, from the terminal Ediacaran Shibantan Member (ca. 551 to ca. 541 million years ago) in the Yangtze Gorges area of South China. These trace fossils represent the earliest known trackways. They consist of two rows of imprints arranged in poorly organized series or repeated groups. These trackways may have been produced by bilaterian animals with paired appendages, although the phylum-level phylogenetic affinity of the trace makers remains unknown. It is possible that the trackways and associated burrows were produced by the same trace maker, indicating a complex behavior involving both walking and burrowing. Together, these trackways and burrows mark the arrival of a new era characterized by an increasing geobiological footprint of bilaterian animals.
- A problematic animal fossil from the early Cambrian Hetang Formation, South China - A replyTang, Qing; Hu, Jie; Xie, Guwei; Yuan, Xunlai; Wan, Bin; Zhou, Chuanming; Dong, Xu; Cao, Guohua; Lieberman, Bruce S.; Leys, Sally P.; Xiao, Shuhai (Cambridge University Press, 2019-11-01)We recently reported Cambrowania ovata Tang and Xiao in Tang et al., 2019, from the early Cambrian Hetang Formation in South China and interpreted it as a problematic animal fossil, possibly related to either sponges or bivalved arthropods (Tang et al., 2019). Slater and Budd (2019) contested our taxonomic identification and phylogenetic interpretation; instead, they claimed that Cambrowania ovata is a large acritarch referable to morphotaxon Leiosphaeridia Eisenack, 1958, and thus is not an animal. Here we refute their criticisms, clarify the differences between Cambrowania and Leiosphaeridia and other acritarchs, and reiterate why an animal affinity for Cambrowania cannot be ruled out.
- Systematic paleontology, acritarch biostratigraphy, and delta C-13 chemostratigraphy of the early Ediacaran Krol A Formation, Lesser Himalaya, northern IndiaXiao, Shuhai; Jiang, Ganqing; Ye, Qin; Ouyang, Qing; Banerjee, Dhiraj M.; Singh, Birendra P.; Muscente, A. D.; Zhou, Chuanming; Hughes, Nigel C. (Cambridge University Press, 2022)Acritarch biostratigraphic and delta C-13 chemostratigraphic data from the Krol A Formation in the Solan area (Lesser Himalaya, northern India) are integrated to aid inter-basinal correlation of early-middle Ediacaran strata. We identified a prominent negative delta C-13 excursion (likely equivalent to EN2 in the lower Doushantuo Formation in the Yangtze Gorges area of South China), over a dozen species of acanthomorphs (including two new species-Cavaspina tiwariae Xiao n. sp., Dictyotidium grazhdankinii Xiao n. sp.), and numerous other microfossils from an interval in the Krol A Formation. Most microfossil taxa from the Krol A and the underlying Infra-Krol formations are also present in the Doushantuo Formation. Infra-Krol acanthomorphs support a correlation with the earliest Doushantuo biozone: the Appendisphaera grandis-Weissiella grandistella-Tianzhushania spinosa Assemblage Zone. Krol A microfossils indicate a correlation with the second or (more likely, when delta C-13 data are considered) the third biozone in the lower Doushantuo Formation (i.e., the Tanarium tuberosum-Schizofusa zangwenlongii or Tanarium conoideum-Cavaspina basiconica Assemblage Zone). The association of acanthomorphs with EN2 in the Krol Formation fills a critical gap in South China where chert nodules, and thus acanthomorphs, are rare in the EN2 interval. Like many other Ediacaran acanthomorphs assemblages, Krol A and Doushantuo acanthomorphs are distributed in low paleolatitudes, and they may represent a distinct paleobiogeographic province in east Gondwana. The Indian data affirm the stratigraphic significance of acanthomorphs and delta C-13, clarify key issues of lower Ediacaran bio- and chemostratigraphic correlation, and strengthen the basis for the study of Ediacaran eukaryote evolution and paleobiogeography. UUID: http://zoobank.org/5289fdb2-0e49-4b3b-880f-f5b21acab371.
- Tonian carbonaceous compressions indicate that Horodyskia is one of the oldest multicellular and coenocytic macro-organismsLi, Guangjin; Chen, Lei; Pang, Ke; Tang, Qing; Wu, Chengxi; Yuan, Xunlai; Zhou, Chuanming; Xiao, Shuhai (Nature Portfolio, 2023-04)Macrofossils with unambiguous biogenic origin and predating the one-billion-year-old multicellular fossils Bangiomorpha and Proterocladus interpreted as crown-group eukaryotes are quite rare. Horodyskia is one of these few macrofossils, and it extends from the early Mesoproterozoic Era to the terminal Ediacaran Period. The biological interpretation of this enigmatic fossil, however, has been a matter of controversy since its discovery in 1982, largely because there was no evidence for the preservation of organic walls. Here we report new carbonaceous compressions of Horodyskia from the Tonian successions (similar to 950-720 Ma) in North China. The macrofossils herein with bona fide organic walls reinforce the biogenicity of Horodyskia. Aided by the new material, we reconstruct Horodyskia as a colonial organism composed of a chain of organic-walled vesicles that likely represent multinucleated (coenocytic) cells of early eukaryotes. Two species of Horodyskia are differentiated on the basis of vesicle sizes, and their co-existence in the Tonian assemblage provides a link between the Mesoproterozoic (H. moniliformis) and the Ediacaran (H. minor) species. Our study thus provides evidence that eukaryotes have acquired macroscopic size through the combination of coenocytism and colonial multicellularity at least similar to 1.48 Ga, and highlights an exceptionally long range and morphological stasis of this Proterozoic macrofossils.
- Transient marine euxinia at the end of the terminal Cryogenian glaciationLang, Xianguo; Shen, Bing; Peng, Yongbo; Xiao, Shuhai; Zhou, Chuanming; Bao, Huiming; Kaufman, Alan J.; Huang, Kangjun; Crockford, Peter W.; Liu, Yonggang; Tang, Wenbo; Ma, Haoran (Springer Nature, 2018-08-01)Termination of the terminal Cryogenian Marinoan snowball Earth glaciation (similar to 650-635 Ma) is associated with the worldwide deposition of a cap carbonate. Modeling studies suggest that, during and immediately following deglaciation, the ocean may have experienced a rapid rise in pH and physical stratification followed by oceanic overturn. Testing these predictions requires the establishment of a high-resolution sequence of events within sedimentary records. Here we report the conspicuous occurrence of pyrite concretions in the topmost Nantuo Formation ( South China) that was deposited in the Marinoan glacial deposits. Sedimentary facies and sulfur isotope data indicate pyrite precipitation in the sediments with H2S diffusing from the overlying sulfidic/euxinic seawater and Fe (II) from diamictite sediments. These observations suggest a transient but widespread presence of marine euxinia in an ocean characterized by redox stratification, high bioproductivity, and high-fluxes of sulfate from chemical weathering before the deposition of the cap carbonate.
- Was the Ediacaran Shuram Excursion a globally synchronized early diagenetic event? Insights from methane-derived authigenic carbonates in the uppermost Doushantuo Formation, South ChinaCui, Huan; Kaufman, Alan J.; Xiao, Shuhai; Zhou, Chuanming; Liu, Xiao-Ming (2017-02)The Ediacaran Period is characterized by the most profound negative carbon isotope (δ13C) excursion in Earth history, the ShuramExcursion. Various hypotheses – including the massive oxidation of dissolved organic carbon (DOC) in the oceans, the weathering of terrestrial organic carbon, or the release and oxidation of methane hydrates and/or expelled petroleum from the subsurface – have been proposed as sources of the 13C-depleted carbon. More recently, it has been suggested that global-scale precipitation of early authigenic carbonates, driven by anaerobicmicrobial metabolism in unconsolidated sediments, may have caused the Shuram Excursion, but empirical evidence is lacking. Here we present a comprehensive analysis of a Shuram-associated interval from the uppermost Doushantuo Formation in South China. Our study reveals petrographic evidence of methane-derived authigenic calcite (formed as early diagenetic cements and nodules) that are remarkably depleted in 13C – suggesting a buildup of alkalinity in pore fluids through the anaerobic oxidation of methane (AOM) – and systematically depleted in 18O relative to co-occurring dolomite. Early authigenesis of these minerals is likely to be driven by increased microbial sulfate reduction, triggered by enhanced continental weathering in the context of a marked rise in atmospheric oxygen levels. In light of the finding of methane-derived authigenic carbonates at Zhongling, and based on our basin-scale stratigraphic correlation, we hypothesize that the marked 13C and 18O depletion (including their co-variation noted worldwide) in the Shuram Excursion may reflect an episode of authigenesis occurring within a sulfate–methane transition zone (SMTZ). If true, the Shuram Excursion was then a global biogeochemical response to enhanced seawater sulfate concentration in the Ediacaran ocean driven by the Neoproterozoic oxidation of surface environments. This paleo-oceanographic transition may have therefore paved theway for subsequent evolution and diversification of animals. Our study highlights the significance of an integrated approach that combines petrography, mineralogy, and texture-specificmicro-drilling geochemistry in chemostratigraphic studies.