Fluvial-deltaic deposition in high accommodation floodplain lakes, Pennsylvanian Appalachian Basin, eastern Kentucky

Abstract

Middle to Upper Pennsylvanian sedimentary rocks in the central Appalachian Basin of Eastern Kentucky contain a significant fluvial component that has been extensively studied in some areas. However, most of the previous work focused on coastal plain sequence stratigraphic analysis and fluvial architecture with little focus on the up-dip fluvial pile. Low energy regime fine-grained sediment dominates the high-accommodation fluvial setting along Highway 23 near Louisa, Kentucky. Relatively high water tables resulted in poorly drained floodplains and the formation of floodplain lakes adjacent to main fluvial channel bodies. Very fine grain sediments, interpreted as floodplain lakes, surround isolated tie channels connecting to the main channels. Thin, discontinuous, fine to very fine grain sand sheets connected to isolated channels represent pulses of subaqueous deposition from tie channel propagation across the lake as a delta. The formation of tie channels from the main channel to floodplain lake deposits creates potential connectivity of otherwise isolated sand bodies. Bisection of the lake by tie channels creates a barrier for sediment transport and resulted in asymmetrical deposition of splay deposits from the main river channel. Examination of these outcrops revealed ancient examples of tie channel deposition into floodplain lakes that can be related to processes seen in modern environments.