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Browsing by Author "Orndorff, William D."

Now showing 1 - 4 of 4
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    Analysis of Hydrologic and Geochemical Time Series Data at James Cave, Virginia: Implications for Epikarst Influence on Recharge
    Eagle, Sarah Denise (Virginia Tech, 2013-05-09)
    Karst aquifers are productive groundwater systems around the world, supplying approximately 25% of the world's drinking water. However, they are highly vulnerable to contamination due to rapid groundwater transit in the transmission zone (KWI 2006). The epikarst, also known as the subcutaneous zone, is an interface between the soil overburden and the transmission zone. The epikarst is considered a critical zone as it can control hydrologic and geochemical characteristics of recharge to the underlying karst aquifer.  The overall goal of this thesis is to utilize time series hydrologic and geochemical data collected at James Cave, Virginia, to examine the influence of epikarst on the quantity, quality, and rates of recharge to aquifers in Appalachian karst. Results of this study indicate a strong seasonality of both the hydrology and geochemistry of recharge. The conceptual model of the epikarst developed in this study identifies three hydrologic seasons: recharge, recession, and baseflow. Seasonality of recharge geochemistry coincides with these three hydrologic seasons.  These results have implications for management of karst aquifers.  First, recharge to Appalachian karst aquifers is seasonal, reaching a maximum during the winter-early spring; the onset of recharge depends on antecedent climatic conditions.  Second, water that infiltrates into the epikarst will have seasonally variable residence times due to changes in hydrologic storage; these variations in attenuation affect geochemical reactions in the epikarst, which can influence recharge quality. Overall, these results point to the complex influence of epikarst on karst recharge, which necessitates collection of long-term and high resolution datasets.
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    Crystalline bedrock geology of the lower Susquehanna Gorge: Conowingo to Havre de Grace, Maryland
    Orndorff, William D. (Virginia Tech, 1996-07-01)
    The crystalline bedrock of the lowermost Susquehanna River Gorge, Conowingo to Havre de Grace, Maryland, consists of two discrete structural blocks, each with its own unique history prior to juxtaposition. The southern Havre de Grace Block is a Cambrian magmatic arc association (James Run Formation and Port Deposit Intrusive Complex), possibly developed on a rift fragment of Laurentia (Canal Road Formation). The northern Conowingo Block represents a precursory mélange (Conowingo Dam Formation) intruded during the Ordovician by a layered mafic complex (State Line Mafic Complex) and associated plutons (Basin Run Tonalite). Many olistoliths within the Conowingo Dam Formation could have originated in the Havre de Grace Block. The Havre de Grace Block was metamorphosed and deformed under amphibolite facies conditions during Middle Ordovician to Early Silurian time. It was subsequently thrust upon the Conowingo Block along the Elbow Branch Thrust, probably during the Late Ordovician or Early Silurian. From as early as the Middle Devonian, through the Pennsylvanian, dextral strike-slip shearing took place under greenschist facies conditions along the Rock Run Shear Zone, within the northern part of the Havre de Grace Block. Analysis of SC fabrics in the zone yields a minimum offset of 2 to 6 kilometers. From Late Paleozoic to Mesozoic time, strike-slip shearing gave way to dip-slip shearing across very thin, low grade, ductile shear zones.
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    James Cave Epikarst Monitoring Drip Data
    Schreiber, Madeline E.; Eagle, Sarah; Schwartz, Benjamin; Orndorff, William D.; Gerst, Jonathan (2013-05-07)
    James Cave is located in Pulaski County, Virginia and formed within the Cambro-Ordovician Conococheague formation. Continuous (10 minute interval) monitoring of cave drip rate and precipitation was conducted from late summer 2007 to winter 2013 using HOBO® tipping bucket rain gauges and multi-station data loggers. At the subsurface sites, drips were collected using tarps with areas of 2.43m2, 3.07m2, and 3.51m2 for MS1, MS2, and MS3, respectively. Precipitation was measured at the surface near the cave entrance.
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    James Cave Epikarst Monitoring Temperature and Specific Conductance Data as of 120701
    Schreiber, Madeline E.; Eagle, Sarah; Schwartz, Benjamin; Orndorff, William D.; Gerst, Jonathan (2013-05-08)
    James Cave is located in Pulaski County, Virginia and formed within the Cambro-Ordovician Conococheague formation. Continuous (10 minute interval) monitoring of specific conductance and water temperature of cave drips and cave stream from January 2011 to winter 2013 using HOBO® conductivity loggers. At the subsurface sites, drips were consolidated using tarps with areas of 2.43m2, 3.07m2, and 3.51m2 for MS1, MS2, and MS3, respectively and funneled into a reservoir for measurement and logging of conductivity and temperature. These data are presented as the temperature compensated specific conductance. Additionally, this submission includes air temperature taken via HOBO® temperature sensors and loggers. The air temperature data are subject to considerable artifacts such as an increase in temperature during sampling events.