Depositional Environments and Facies Analysis of the Cherokee Group in West-Central Kansas

Abstract

The Cherokee Group of early Desmoinesian Pennsylvanian age in west-central Kansas is comprised of a mixed siliciclastic and carbonate sequence. It was deposited in environments that are transitional from continental to marginal marine as the Hugoton Sea transgressed the Mississippian unconformity on to the Central Kansas uplift. Sandstones of the Cherokee Group are important oil reservoirs in west-central Kansas, but they are highly variable and difficult to predict. Core studies and subsurface analysis reveal two persistent and widespread limestone beds that form useful stratigraphic markers within the Cherokee. They provide a framework for facies analysis and regional mapping that may be useful as a predictive tool for oil exploration. Six basic lithofacies are interpreted from lithologies and sedimentary structures observed in cores obtained from four wells in eastern Ness County: (1) basal Pennsylvanian conglomerate, (2) fluvial sands, (3) fine-grained tidal flat deposits, (4) shallow-marine limestones, (5) shoreline sands and tidal channel sands, and (6) braided stream, sandy conglomerates. These facies are correlative with components of an ideal Kansas cyclothem. Two transgressive-regressive cycles are identified and maximum transgression is correlated with two widespread limestone beds. Following burial of the Mississippian karstic surface, deposition of peritidal sediments occurred on a uniform shallowmore » shelf, punctuated by periods of subaerial exposure and weathering. Clastics derived from the eroding Central Kansas uplift were probably supplied to the coastal plain by braided streams and reworked by coastal processes.« less