Abstract

Three successive stratigraphic units in the Upper Ordovician strata of the central Appalachians represent the subaqueous portion of a deltaic sequence deposited by a band of coalescing small deltas which pro-graded westward during the Taconic uplift. The basal unit consists of graded sandstone and fossiliferous shale. The graded sandstones are interpreted to be turbidites which accumulated as the bottom-set beds of the coalescing deltas. The medial unit exhibits slump features and consists chiefly of unlaminated, fossiliferous, poorly sorted, clayey sandstone and siltstone. This unit is interpreted as a deltaic fore-set slump deposit whose unstable content was the source material for turbidity currents. The upper unit consists of sparingly fossiliferous silty shale interbedded with laminated sandstone and other rock types which are inferred to be the top-set portion of the subaqueous deltaic sequence.

Unfossiliferous cross-bedded sandstone and coal(?)-bearing shale overlying the upper unit probably represent the subaerial top-set beds of the coalescing deltas.