The Pennsylvanian foreland province of Texas and eastern New Mexico covers approximately 150,000 square miles. Over this whole area close relationships exist between structural and sedimentary developments. Originally a marginal segment of the mid-Paleozoic craton, it was isolated from the ocean by borderland mountain ranges. Uplift of these Llanorian ranges altered the early continental shelf block into an incipient mediterranean, notching deeply into the cratonic core. The eastern margin of this intra-continental seaway was almost continuously loaded with clastic sediments. Extensive limestone banks spread across the unloaded marginal shallows farther west. Uplifted positive blocks and topographic highs within the negative interior supported isolated limestone buildups. Intervening clastic and carbonate-starved deeps accumulated thin sections of dark shales. Facies changes associated with environmental boundaries limit embayment stratigraphic correlations.
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Rocks of the Pennsylvanian System are the bed rock of approximately 10 per cent of the land area of continental United States. These rocks yield 17 per cent of the petroleum, most of the coal, and most of the ceramic raw material of the United States.
Areas of deposition of Pennsylvanian rocks are naturally discriminated as the New England trough, the Appalachian trough, the Eastern Interior basin, the Michigan basin, the Western Interior basin, the Ardmore basin, the Ft. Worth syncline, the Permian basin, the Rocky Mountain geosyncline, and the Cordilleran trough. These genetic areas and the Ouachita fold belt are the regions described.
The Pennsylvanian System in Michigan has been described in detail by W. A. Kelly (Mich. Geol. Survey, Pub. 40, part 2, p. 155-226, 1936). The section is truncated and consists of the Parma sandstone (below), the Saginaw group of cyclical formations, and the Grand River group, which contains red sandstones and gypsum. The Parma and Saginaw are Pottsvillian in age; possibly, Atokan and Desmoinesian. The Grand River, placed by some geologists in the Permian, is probably early Missourian.
The project for a special volume was initiated in 1953, at which time it was decided that the Springer Series was tobeconsidered as Pennsylvanian, the Wolfcamp and Admire-Council Grove-Chase, as Permian. Evidence has since accumulated that the Springer is Mississippian, that the Ouachita Jackfork and Stanley are Mississippian, that the Dunkard is, atleast in part, Pennsylvanian, and that the “Lyon series” and Wolfcamp formation might better be classed