This paper outlines the petrology and paleogeography of the Greenbrier formation of Mississippian age, as determined from study of well samples, insoluble residues, heavy minerals, and thin sections. In the Greenbrier, clastic limestone beds composed of calcareous 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 near-shore sediments and in part probably are ancient bar, beach, channel, and dune deposits and have the shapes and trends characteristic of such deposits. About half of the production of oil and gas from the Greenbrier is from clastic limestones; about half from dolomite and dolomitic limestone.

Dolomite and dolomitic limestones are largely confined to the basal 20-30 feet of the formation. This basal zone appears to transgress both structure and time units. 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 sedimentary sources on the north. Earlier Mississippian and Upper Devonian sands of West Virginia, Ohio, and Pennsylvania were not important sources of the quartz sand.

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