--> Abstract: The Upper Pennsylvanian Indian Cave Sandstone: Lithostratigraphy, Architecture and Sequence Stratigraphy of Potential Reservoi; #90063 (2007)

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The Upper Pennsylvanian Indian Cave Sandstone: Lithostratigraphy, Architecture and Sequence Stratigraphy of Potential Reservoirs in the High Midcontinent Shelf Platform, USA

 

Fischbein, Steven A.1, Christopher R. Fielding2, R. Matthew Joeckel2 (1) Nebraska Department of Environmental Quality, Lincoln, NE (2) University of Nebraska-Lincoln, Lincoln, NE

 

Incised sandstone bodies in the uppermost Pennsylvanian Admire Group in southeastern Nebraska are encased in marine shale-limestone cyclothems. These bodies are erosionally bounded, channel form units of trough cross-bedded sandstone grading vertically into mudstone-and sandstone-dominated heterolith. Bounding surfaces within bodies, floored with heterolithic clast conglomerates, are interpreted as storey boundaries. Basal erosion surfaces, interpreted as sequence boundaries, juxtapose mudrock-carbonate clast conglomerates or trough cross-bedded sandstones unconformably over marine shale-limestone cyclothem strata. Systems tracts are delineated within bodies through major facies associations interpreted as tidally influenced fluvial and upper estuarine.

Sequence boundaries correlated in outcrop to areas where sandstone bodies are absent but paleosols are preserved at the equivalent horizon are interpreted as correlative conformities to the sequence boundaries. These correlations offer evidence for the regional continuity of sequence boundaries along which further such channelized sandstone bodies may be preserved.

 

Reclassification of the “Indian Cave Sandstone” into at least four incised-valley-fills (IVF) offer evidence of reservoirs in the high Midcontinent platform that have to date seen only minimal investigation. These potential reservoirs are architecturally similar to the Tonganoxie Sandstone in eastern Kansas and Morrow IVF sandstones of eastern Colorado and western Kansas, although significantly further up-depositional dip. Units identified as “Indian Cave Sandstone” located within equivalent stratigraphic position but significantly down depositional dip contain recoverable quantities of oil and gas. As such, in regions where an uppermost Pennsylvanian subcrop is identified, and a high shelf platform position is interpreted, incised valley fill networks are potential reservoirs and appropriate hydrocarbon exploration targets.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California