The general stratigraphic results of detailed field investigations covering a large part of the Arkansas-Oklahoma coal basin are briefly summarized. Isopach maps of the Atoka, McAlester, Savanna, and Boggy formations show that the maximum thickness of the Atoka formation is somewhere southeast of the coal basin, that the thickest parts of the McAlester and Savanna formations lie a short distance north of the Choctaw fault, and that all of the formations thin westward and northward. There are unconformities at the base of the Hartshorne and Savanna sandstones. Much of the deposition was marine in the western part and continental or very shallow water in the eastern part of the coal basin. The source of the sediments is believed to be (1) Llanoria, (2) the previously deposited Stanley, Jackfork, and Atoka of the Ouachita Mountains, (3) the Arbuckle Mountains, and (4) an uplift of rocks resembling those of the Arbuckle Mountains which, in Pennsylvanian time, stood near the present location of Black Knob Ridge. Minor structural movements occurred within the coal basin during the time of deposition of the formations. The Atoka formation is of Pottsville age, and the Hartshorne, McAlester, Savanna, and Boggy formations are of Allegheny age.