Bruce R. Wardlaw 1977 The Gerster Limestone contains three minor lithofacies: the packstone, wackestone, and mixed facies, differentiated largely on the basis of the carbonate matrix and mud content of the rocks. Five biostratigraphic zones ranging in age from Roadian-Wordian to Wordian are, in ascending order, the Thamnosia, Kuvelousia, transition, Yakovlevia, and upper zones. The Gerster was probably deposted in a protected coastal basin separated from the Phosphoria Basin by a shallow marine positive area. The brachiopod fauna is divided into fifteen bioassociations. The fauna is part of a continental margin suite of faunas distributed from west Texas to the Canadian Arctic and belongs to the Tethyan-nonreef biogeographica[ province. application/pdf 10.3133/ofr77470 en U.S. Geological Survey, The biostratigraphy and paleoecology of the Gerster limestone (Upper Permian) in Nevada and Utah reports