--> --> A GIS Based Sequence Stratigraphic Analysis of the Mississippian Big Lime, West Virginia, U.S.A Wynn, Thomas C., and Read, J. Fred , #90044 (2005).

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A GIS Based Sequence Stratigraphic Analysis of the Mississippian Big Lime, West Virginia, U.S.A

 

Wynn, Thomas C.1, and Read, J. Fred 2,

1Dept. of Geology and Physics, Lock Haven University, Ulmer Hall, Lock Haven, PA 17745

2Dept. of Geosciences, Virginia Tech, 4044 Derring Hall, Blacksburg, VA 24061.

 

The Mississippian Big Lime (Greenbrier Group) of West Virginia is a 100 to 1600 feet thick succession of mixed carbonate-siliciclastic sediments that formed on the Appalachian foreland.  It provides an outcrop and subsurface analog to better understand Mississippian three-dimensional facies distribution, reservoir stacking patterns, and the stratigraphic signature of global greenhouse to icehouse conditions within an active foreland setting.  Well-cuttings and wireline logs from 200 relatively shallow wells throughout West Virginia were analysed utilizing GIS. Fifteen regional fourth-order sequences were mapped throughout the subsurface, and time-slice maps produced. Lowstand-early transgressive tracts on the ramp consist of a complex mosaic of redbeds adjacent tectonic highlands, barrier sands along the ramp margin, and lagoonal shales and quartz peloid grainstone eolianites. Highstand tracts consist of widespread lagoonal carbonate mudstone, interspersed with three variably developed ooid and skeletal grainstone belts located along the ramp margin, within the lagoon, and along the updip shoreline; the ramp margin facies pass downdip into dark skeletal wackestone and then into dark gray laminated argillaceous carbonates. Thickness trends and complex distribution of grainstone facies and re-entrants in the margin suggest a tectonic control on facies distribution associated with the complexly faulted foreland, while the major sequence development reflects 4th order eustasy driven by waxing and waning of Gondwanan ice-sheets.  This sea level control is further evidenced by deep water slope facies with low-stand deposits in Virginia, and their C-O isotope signature, all of which suggest significant periodic fourth order sea level changes during deposition.