ABSTRACT

The Greenbrier Group of eastern West Virginia consists of marine carbonates interbedded and mixed with siliciclastics that were deposited on a shallow shelf in the Late Mississippian. The Denmar Formation is the lowest unit of the Greenbrier Group present in east-central West Virginia, and it represents a shallow tidal-flat and platform sequence deposited by a transgressing sea during the Meramecian. This transgression was followed by a regression with progradation of Taggard Formation terrigenous clastics onto restricted tidal flats during the earliest Chesterian.

The Denmar tidal-flat deposits are characterized by pelleted mudstones, limited and depauperate fauna, calcite-filled and dolomite-filled geodes, caliche crusts, fenestral structures, dolomite, burrows, and channel deposits. The platform deposits include more diverse fauna, less micrite, cross-bedded and massive oolitic grainstones, and cross-bedded quartzarenites. Most of the siliciclastics were derived from the north and east of the Appalachian basin. Additional quartz silt, sand, and pebbles were eroded from an uplifted area within the basin and were incorporated into the tidal-flat and platform sediments. This Meramecian tectonic uplift, considered to be part of the 38th parallel lineament, created a subaerial and submarine topographic high that affected sedimentation patterns during the remainder of Greenbrier deposition.

Early phreatic cementation occurred along the flank of the uplift in at least two stages. There is evidence of both penecontemporaneous and later replacement dolomite. In certain strata in the western outcrops, hydrocarbons migrated through permeable layers and filled remaining pores.

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