The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Shen Kefeng - One of the best experts on this subject based on the ideXlab platform.
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Genetic models and exploration implication of the Paleochannel sandstone-type uranium deposits in the Erlian Basin, North China – A review and comparative study
Ore Geology Reviews, 2020Co-Authors: Nie Fengjun, Yan Zhaobin, Feng Zhibing, Li Mangen, Xia Fei, Zhang Chengyong, Wang Yanguo, Jianxin Yang, Kang Shihu, Shen KefengAbstract:Abstract Since the Bayanwula uranium deposit was discovered, several Paleochannel sandstone-type uranium deposits have been found in the Manite and Wulanchabu sub-basins of the Erlian Basin. The Paleochannel sandstone-type uranium deposits in the Erlian Basin represent important uranium sources in North China. The regional geological settings, depositional facies and sequences, ore-bearing sand bodies and uranium source rocks (e.g., granite and sandstones), play important roles in the formation of these deposits. Three styles of Paleochannel sandstone-type uranium deposits occur in the Erlian Basin: 1) interlayer oxidation-style deposit hosted in the braided river sand bodies of the Saihan Formation and characterized by laterally zoned mineralization; 2) phreatic oxidation -style deposits hosted in meandering river sand bodies of the Saihan Formation, showing vertically zoned oxidized mineralization; 3) superimposed mineralization -style deposits hosted in braided river sand bodies of the Saihan Formation, characterized by an oxidized zone from fluvial channel center to margin, which was then overprinted by hydrothermal fluids. These three styles of the uranium deposits depend on depositional microfacies and development of deep-seated faults, which can be used to locate the mineralization and exploration targets within the Erlian Basin.
John F. Wehmiller - One of the best experts on this subject based on the ideXlab platform.
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Seismic-Reflection Identification of Susquehanna River Paleochannels on the Mid-Atlantic Coastal Plain
Quaternary Research, 1994Co-Authors: Robert B. Genau, John A. Madsen, Susan Mcgeary, John F. WehmillerAbstract:Abstract Land-based, high-resolution seismic-reflection methods were used to image Quaternary Paleochannels of the Susquehanna River system. Using a portable, 12-channel signal-enhancing seismograph, 12 accelerometers as receivers, and a 4.54-kg sledge hammer struck against an aluminum plate as a source, a sixfold, multichannel seismic profile 2.5 km long was acquired at Taylors Island, Maryland. On the processed seismic profile, pronounced high-amplitude seismic reflections delineate the unconformity between Quaternary and underlying Tertiary sediments and the disconformable contact separating Miocene and Eocene deposits. Subsurface-seismic stratigraphic relationships that clearly indicate the presence of two Paleochannels were observed, one believed to be the Exmore Paleochannel, projected to underlie northern Taylors Island based on marine seismic data. An overlapping sequence of fill sediments was observed on the eastern margin of the Exmore Paleochannel. The second Paleochannel may be a tributary of the Exmore or possibly the western edge of the younger Eastville Paleochannel. Results from this study indicate that land-based, shallow, high-resolution seismic-reflection data can be used to delineate subsurface geomorphology successfully in coastal plain environments. This technique of defining erosional surfaces and depositional units beneath present land areas, when integrated with chronostratigraphic data, is a powerful tool for developing a better understanding of the Quaternary record.
Nie Fengjun - One of the best experts on this subject based on the ideXlab platform.
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Genetic models and exploration implication of the Paleochannel sandstone-type uranium deposits in the Erlian Basin, North China – A review and comparative study
Ore Geology Reviews, 2020Co-Authors: Nie Fengjun, Yan Zhaobin, Feng Zhibing, Li Mangen, Xia Fei, Zhang Chengyong, Wang Yanguo, Jianxin Yang, Kang Shihu, Shen KefengAbstract:Abstract Since the Bayanwula uranium deposit was discovered, several Paleochannel sandstone-type uranium deposits have been found in the Manite and Wulanchabu sub-basins of the Erlian Basin. The Paleochannel sandstone-type uranium deposits in the Erlian Basin represent important uranium sources in North China. The regional geological settings, depositional facies and sequences, ore-bearing sand bodies and uranium source rocks (e.g., granite and sandstones), play important roles in the formation of these deposits. Three styles of Paleochannel sandstone-type uranium deposits occur in the Erlian Basin: 1) interlayer oxidation-style deposit hosted in the braided river sand bodies of the Saihan Formation and characterized by laterally zoned mineralization; 2) phreatic oxidation -style deposits hosted in meandering river sand bodies of the Saihan Formation, showing vertically zoned oxidized mineralization; 3) superimposed mineralization -style deposits hosted in braided river sand bodies of the Saihan Formation, characterized by an oxidized zone from fluvial channel center to margin, which was then overprinted by hydrothermal fluids. These three styles of the uranium deposits depend on depositional microfacies and development of deep-seated faults, which can be used to locate the mineralization and exploration targets within the Erlian Basin.
Andrew C. Scott - One of the best experts on this subject based on the ideXlab platform.
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Paleoecology of the Springfield Coal Member (Desmoinesian, Illinois Basin) near the Leslie Cemetery Paleochannel, southwestern Indiana
International Journal of Coal Geology, 1995Co-Authors: Debra A. Willard, William A. Dimichele, Donald L. Eggert, James C. Hower, Carl B. Rexroad, Andrew C. ScottAbstract:Abstract The Springfield Coal Member (Carbondale Group, Petersburg Formation of Indiana) is split locally in Warrick and Gibson Counties, Indiana, by clastic rocks of the Folsomville Member (Carbondale Group, Petersburg Formation) that represent the Leslie Cemetery Paleochannel, part of a large, interconnected Paleochannel system in the Springfield coal bed. This study incorporated analysis of miospore and megaspore assemblages, coal petrography, plant compression fossils and conodonts from the coal and clastic split to document changes in the swamp and its vegetation in response to the activity of the Leslie Cemetery Paleochannel. Palynological and petrographic data indicate that environmental conditions and vegetation in the lower bench of coal near the Leslie Cemetery Paleochannel were similar to those found in profiles through the coal bed at sites near the larger, more extensive Galatia Paleochannel. Miospore floras of the high-vitrinite, lower bench of coal were dominated by tree-fern miospores, with those of lycopsids ranking second in abundance; megaspore assemblages were dominated by lycopsid megaspores. Near the contacy between the lower bench of coal and clastic split, medullosan prepollen increases in abundance and fusain bands are more common, which may indicate the occurrence of fire, either within or outside the swamp. Vegetation in the Folsomville Member and upper bench of coal differ markedly from that of the lower bench of coal. Plant megafossils from the Folsomville Member indicate dominance by pteridosperms and/or lycopsids and Folsomville Member miospore assemblages are dominated by lycopsid miospores most typically found in mudstones, including Lycospora torquifer and higher than normal abundances of Granasporites medius . In the transition from clastic rocks of the Folsomville Member to the upper bench of coal, miospores of ‘ecotonal’ lycopsids ( Paralycopodites ) reach their peak abundance, pteridosperms dominate megafossil assemblages and inertinite levels are relatively high. At higher levels of the upper bench of coal, vitrinite levels are higher and miospore assemblages are dominated by lycopsid miospores typical of coal swamps ( Lycospora granulata, L. pusilla ). The presence of conodonts in coalballs in the upper bench of coal and spirorbid worms in the split indicate that the paleoswamp may have received some marine or brackish water influence. Higher than normal salinity levels may explain the vegetational changes observed in the upper bench of coal near the Leslie Cemetery Paleochannel.
Daniel Lizarralde - One of the best experts on this subject based on the ideXlab platform.
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The role of Paleochannels in groundwater/seawater exchange
Journal of Hydrology, 2007Co-Authors: Ann E. Mulligan, Rob L. Evans, Daniel LizarraldeAbstract:Relict fluvial channels that are infilled with high permeability sediments act as preferred pathways for groundwater flow and solute transport. In coastal regions, such Paleochannels can provide a hydraulic connection between freshwater aquifers and the sea, facilitating saltwater intrusion landward or freshwater discharge offshore. Although Paleochannels have been implicated in several instances of saltwater intrusion, there has been little direct study of these channels to confirm their role. In this work, simulation modeling of a general multi-layered, coastal-plain-aquifer setting indicates that when a Paleochannel breaches a confining unit offshore, submarine groundwater discharge of intermediate salinity occurs. This discharge is largely concentrated along the margins of the channel. Conversely, seawater inflow occurs along the channel axis, resulting in higher salinity in the middle of the channel relative to the flanks. Chirp seismic and electromagnetic data collected offshore Wrightsville Beach, NC, USA, confirm these simulation results and indicate fresher porewater along channel flanks and slightly higher porewater salinity along the channel axis. Hence, Paleochannels contribute to the spatial variability in submarine groundwater discharge by serving as conduits of focused fluid exchange. Simulations also reveal that the freshwater/saltwater transition zone is closer to land below Paleochannels than in locations with a continuous confining unit. This indicates that such channels are likely to be significant modes of saltwater intrusion into confined aquifers when excess freshwater extraction occurs on land.