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Tectonic patterns had a significant influence on the late Paleozoic Berea, Loyalhanna, and Pittsburgh-Sewickley sandstone units in western West Virginia. The depocenter was in the southwest during Early Devonian Berea deposition, southeast when the Mississippian Loyalhanna (Big Injun) sands filled submarine valleys, and northwest during Late Pennsylvanian when the Pittsburgh and Sewickley (Monongahela Group) deltaic sandstones were deposited.
Western West Virginia tectonically was on a relatively stable platform west of the Appalachian trough. Relative rates of supply and subsidence in the trough influenced the major changes in regional paleoslopes. Shallow downwarped axes on the platform oriented perpendicular to the trough also exerted a subordinate but important tectonic control on sedimentation. Characteristics of shallow-water deposition are shared by the Berea, Loyalhanna (Big Injun), and Monongahela sandstone units. However, the interpreted submarine valley-fill depositional environment of the Loyalhanna (Big Injun) is considerably different from the deltaic environment suggested for the Berea and Monongahela sandstones.
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