This paper describes the petrology and paleogeography of the Mississippian Greenbrier formation as determined from study of well samples, insoluble residues, heavy minerals, and thin sections. In the Greenbrier formation, clastic limestone beds composed of lime sand, oolites, and quartz sand alternate with beds of fine-grained limestone in which clastic texture is indistinct or can not be recognized. The clastic limestones appear to be nearshore sediments and in part are probably ancient bar, beach, channel, and dune deposits and have the shapes and trends characteristic of such deposits. Approximately half of the production of oil and gas from the Greenbrier formation is from clastic limestones; half from dolomite and dolomitic limestone, which are largely confined to th basal 20-30 feet of the Greenbrier formation. This basal zone appears to transgress both time units and structure. The dolomite clearly replaces limestone. Four methods by which magnesium-bearing waters could be introduced into the formation are suggested and the probable pattern of dolomitization resulting from each method is considered.

The quartz sand in the Greenbrier was derived from two or more different sources on the north. Neither earlier Mississippian nor Upper Devonian sands of West Virginia and adjacent parts of Ohio and Pennsylvania were important sources of the quartz sand.