Mississippian rock reservoirs in western Kansas have produced large quantities of oil and gas. The potential for additional production of hydrocarbons is great both at the top of and within the sequence of rocks.

In western Kansas, Mississippian rocks, all marine (except for some Chesteran rocks) and all in the subsurface, are correlated with rocks of the Kinderhookian, Osagian, Meramecian, and Chesteran States. Unconformities set off dominantly carbonate Mississippian rocks from Pennsylvanian rocks above and Cambrian to Devonian rocks below.

Diagenetic alterations, facies changes, and karst complicated the establishment of lateral stratigraphic equivalents. Dolomitization, silicification of fossils, and chertification are widespread.

Conodont faunas recovered as acetic acid insoluble residues from cores are correlated with conodont biostratigraphic zones of the type area of Mississippian rocks. Reworked Devonian and Kinderhookian conodonts preserved in Kinderhookian rocks are evidence that part of the study area once contained Devonian rocks.

The primary sediment source of Osagian and Meramecian rocks was biogenetic. Sediments were deposited in warm, shallow seas which fluctuated in depth. Thin intraformational conglomerate beds, quasibrecciated limestone beds, and local beds of anhydrite are known in upper Meramecian rocks. An increased content of clastic (quartz) rocks in upper Meramecian strata marks an important change in sediment source. Areas of provenance of siliceous sediments were the Central Kansas uplift and the Las Animas arch. In Chesteran rocks, sandstone, siltstone, and thin limestone beds predominate.

A normal sequence of Osagian and Meramecian rocks was deposited in south-central Kansas but was diagenetically altered. The cherty “Cowley” facies, developed only locally, includes rocks of Osagian and Meramecian ages. The term “Cowley Formation” should be dropped.

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