A triangular area of approximately 35,000 square miles of normal Paleozoic sediments occupies a large part of northern Mississippi and northwestern Alabama. The Black Warrior basin, as its extension is herein proposed, is bounded on the east by the southwesterly plunging Appalachian folds; on the south and southwest by the southeasterly plunging Ouachita mountain system; and on the north by the high Ordovician areas in central and western Tennessee. A soft cover of Mesozoic and Tertiary sedimentary deposits ranges from a feather edge at the Paleozoic outcrop in the northeastern part of the area to 6,000 feet in central Mississippi. Several hundred test wells have penetrated Paleozoic sedimentary rocks ranging in age from Cambro-Ordovician to Pennsylvanian. The combined to al thickness of sedimentary rocks penetrated by these wells is about 12,000 feet. Other than a test well in Webster County, Mississippi, which questionably encountered acidic igneous rock, no igneous or metamorphic rocks have been found in the basin. In the Ouachita boundary area south and southwest of the basin, basaltic intrusions, probably Mesozoic in age, are common in more or less metamorphosed sediments of Paleozoic age. Commercial gas production from Silurian, Mississippian, and Pennsylvanian rocks has been insignificant; but the numerous showings of gas and oil, combined with many sharp unconformities and marked lateral lithologic changes, together with many known faults and anticlinal structures, make the Black Warrior basin one of the large remaining undeveloped potential oil- nd gas-producing provinces of the North American continent.