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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 16 of 16 for “"aquitard"”.
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Hydrogeology and groundwater geochemistry of two glacigenic aquitard/aquifer systems in north-central and south-central Minnesota
… state. Vertical leakage through overlying till aquitards is largely unknown, causing uncertainty in predicting aquifer sustainability. As part of a study of confined aquifer sustainability, the U.S. Geological Survey, Iowa State University, and Minnesota agencies have investigated vertical …
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Sampling for volatile organic compounds from an aquitard: A field evaluation of screen length, purging method, and sampling time
… samples from monitoring wells sited in an aquitard contaminated with volatile organic compounds (VOC); Two well-purging methods--(1) pump to the bottom of the screened interval and (2) pump to the top of the screened interval--were evaluated on three monitoring wells with different screened …
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Analysis of a Multi-Aquifer System in the Southern Coastal Plain of Virginia by Trial and Error Model Calibration to Observed Land Subsidence
… reflect the nature of the complex multi-aquifer/aquitard system in the Coastal Plain. Franklin, Virginia and Suffolk, Virginia extensometers were deactivated in 1995 and were reactivated in 2016 along with the addition of a high-sensitivity borehole extensometer in Nansemond, Virginia in …
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The distribution of vertical groundwater flow in the saturated zone of the Yucca Mountain area: A cross-sectional finite element model
… and lower carbonate aquifer separated by an aquitard with an alluvial aquifer down-gradient. Results indicate that some groundwater flows beneath the high-gradient (low conductivity) zone through the carbonate aquifer. The volcanic aquifer, south of the high gradient zone, must be supplied …
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Evaluation of purging methods when sampling for volatile organic compounds from low-yield monitoring Wells
… screen surrounded the borehole and simulated an aquitard or low-permeability aquifer. This apparatus was placed in a tank filled with chlorobenzene and 1,1,1-Tricholorethane-spiked water. The experiments included the purging procedures mentioned above. Samples were collected before purging, …
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Field Investigation of Stream-Aquifer Interactions: A Case Study in Coastal California
… laterally discontinuous very low-permeability aquitard of silt and clay above which lies Scotts Creek. The aquitard reduces the hydraulic connection between the stream and pumped aquifer resulting in a low and steady streamflow depletion rate over the short term. These results are particularly …
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Methods for Evaluating Aquifer-System Parameters from a Cumulative Compaction Record
… including the distinction between aquifer and aquitard parameters, as the three temporal stresses influence the compaction record uniquely. Maximum cross-correlation was used to determine the hydrodynamic lag between changing water-levels and subsidence within the seasonal signal while …
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Structural diagenesis of bed-parallel and bed-normal fractures, Cretaceous Crato Formation carbonate rocks, NE Brazil
… reservoirs and its role as a semi-permeable aquitard in the Araripe Basin. Permeable pathways in the microbial laminites of the Crato Formation were enhanced first by fracturing caused by elevated fluid pressures, next by fracturing caused by increasing overburden related to burial, next by …
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Effects of lateral heterogeneity on 1D D.C. resistivity and transient electromagnetic soundings in Kuwait
… obtain the top of the Dammam formation - or the aquitard on top of the Dammam - as the model half-space depth at approximately 100 m below the surface in both data sets.
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Denitrification and organic carbon in a series of riparian buffers in the Bear Creek National Demonstration Watershed
… 2002) at five depths up to the non-permeable aquitard (3-4m). Sampling was done following soil morphological features, from the surface, throughout the rest of the vadose zone, at the border with fluctuating groundwater conditions evidenced by mottling, throughout the mottled zone, and at the …
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Lithostratigraphic and structural controls of uranium mineralization in the Kiggavik East Zone, Centre Zone, and Main Zone deposits, Thelon Basin, Nunavut
… while the quartzite served as an overlying aquitard. Phase 2 mineralization resulted from the reactivation of these structures, when remobilizing fluids redistributed uranium along planar brittle structures. In addition to the Hudson and Kivalliq granites, felsic Snow Island Suite rocks may …
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Novel Insights into the Hydrogeochemical Evolution of Groundwater within the Transboundary Milk River Aquifer
… input from either the underlying Colorado aquitard or low-permeability matrix zones within the Milk River Formation. A hydro-geochemical assessment of 774 groundwater samples from 549 wells identifies three sequential hydro-geochemical zones along fracture-controlled flow paths. Zone 1, …
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Geochemical modeling of diagenesis, hydrothermal alteration, and unconformity-related uranium mineralization in the Athabasca Basin, Saskatchewan, Canada
… top of the sandstone succession below a mud-rich aquitard is characterized by extensive quartz overgrowths, whereas the basal part contains little cement and shows extensive dissolution features. Reactive transport modeling indicates that such a quartz cementation-dissolution pattern can be …
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Subsurface dolomitization and porosity occlusion within Early to Middle Ordovician strata of the Illinois Basin, USA
… makes the surface act as an efficient aquitard. A suite of 61 polished thin sections were analyzed petrographically in plane light, polarized light, and with cathodoluminescence (CL). Use of CL allowed identification of an early quartz cement and two dolomite cements (D1 and D2) that …
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Structural geology and geochemistry of sedimentary rock-hosted gold in the eastern Nadaleen Trend, Yukon Territory, Canada
… zone are interpreted to have acted as an aquitard below which ore fluid migrated updip. Within the eastern Nadaleen Trend, ore fluid migration was concentrated into hinge zones of SSW-plunging anticlines, which may have acted as local fluid conduits. One of the Au zones, the Conrad zone, …