Regional Stratigraphic Analysis of Pennsylvanian and Permian Rocks in Western Mid-Continent, Colorado, Kansas, Oklahoma, Texas

ABSTRACT Isopach and lithofacies studies show that the typical Pennsylvanian and Permian sediments in the western Mid-Continent (Colorado, Kansas, Oklahoma, Texas) consist of limestones on the shelf area, and dark shales and blanket sandstones in the Anadarko basin; shelf-to-basin facies changes are abrupt. These deposits are considered the product of a tectonically controlled marine advance from the Ardmore-Anadarko basin foredeep, and retreat toward the West Texas region. During the transgressive phase the Anadarko basin subsided and expanded. As a result, Morrow, Atoka-Des Moines, and Missouri sediments onlapped the shelf area; Marmaton and Missouri shelf-limestone to basin-shale facies changes were located progressively shelfward; and the Cottage Grove, Tonkawa, and Lovell blanket sandstones in the Anadarko basin successively increased in areal extent. During the regressive phase the Anadarko basin gradually ceased to subside, diminished in areal extent, and became an embayment of the Permian basin on the southwest; consequently, Virgil and Wolfcamp shelf-limestone to basin-shale facies changes were located progressively basinward, the Elgin and Laverty Sandstones in the Anadarko basin decreased successively in areal extent, and semi-continental elastics and evaporites were deposited over the western Mid-Continent as the sea withdrew toward the southwest.