Stratigraphy of the Lower Part of the Council Grove Group (“early Permian”) in Southeastern Nebraska and Eastern Kansas

The rocks of the lower part of the Council Grove Group (“Early Permian”) have been examined along their outcrop belt from the small town of Roca in southeastern Nebraska, south to a point near the Kansas-Oklahoma line. The classification, correlation, depositional environments, and cyclic sedimentational patterns of these strata are based on the detailed investigation of fifty selected exposures in the region. The stratigraphic units considered are from just below the base of the Americus Limestone Member upward into the lower part of the Roca Shale Formation.These sediments differ from those of the underlying Admire and Virgil Groups in that limestones are more persistent, whereas true coals, sandstones and conglomerates are generally absent, and the shales are more vividly colored.They can be traced quite easily from exposures in southeastern Nebraska into east-central Kansas. However, in the southern part of Kansas a marked change in thickness and lithology occurs in the Foraker Limestone and Red Eagle Limestone Formations. An interpretation of the environmental conditions under which these strata were deposited is made from the physical characteristics and organisms found in the sediments. A definite vertical prepetition in lithology is evident in the lower part of the Council Grove Group, similar to that of the Admire and Virgil. The principal grouping of lithologies is termed the Early Council Grove Megacyclothem Advisor: T.M. Stou