St. Louis limestone, stratigraphy and petrography, near its type locality

The St. Louis Limestone of the Upper Meramecian Series, Mississippian System, is typically lithographic, light-to light-olive gray in color, dense, and fractures conchoidally. It is brecciated, especially in the lower part, and contains some chert nodules. Oolites are present close to the top of the formation. The Salem-St. Louis contact is placed at the base of the lowest breccia zone and the top of Salem is characterized by crystalline quartz and abundance of chert nodules. The appearance of typical Ste. Genevieve oolites with sand-size quartz grains indicates the St. Louis-Ste. Genevieve contact. The St. Louis Limestone is characterized by dominance of fine-grained texture (micritic) with fossil fragments and minor spar. Foraminifers and bryozoans are the main fossil constituents followed by algae, crinoid fragments and corals. Of the corals, Lithostrotionella and Lithostrotion are significant but of less obvious correlative value. Brachiopods and gastropods are present but to a lesser extent. The formation has about 3 to 5 percent insoluble residues (except close to the boundaries), consisting mostly of quartz. The degree of dolomitization is widely variable from one section to another. The St. Louis Limestone is high in CaD content except in the dolomitized zones. The explanation of the origin of brecciation in the St. Louis Limestone presents some difficulty. The St. Louis Limestone is tentatively subdivided into three units. The deposition of limestone was continuous from Salem through St. Louis time under quiet and shallow water environments. In the study area, the St. Louis Limestone is used for cement manufacture and road construction --Abstract, page ii