Revision of Pierre Shale of Central South Dakota

Abstract

ABSTRACT The stratigraphic subdivision of the Pierre shale in South Dakota is still in a stage of development many revisions having been made of the original units proposed by Searight in 1937. In the present revision a classification is presented that conforms to rules of the Stratigraphic Code. Three subdivisions of the Sully member, as used by the South Dakota Geological Survey, have been raised to member rank and the term Sully has been discarded. The Agency-Oacoma zone of Gries has been redefined and renamed the DeGrey member of the Pierre shale.