Late studies of the Mississippian formations of southeastern Iowa for the Iowa Geological Survey have shown that these formations were tilted to the southwestward and partly truncated in late Mississippian time. There is convincing evidence that this tilting was related to deformation over a wide area in southern Iowa, southeastern Nebraska, eastern Kansas and north western Missouri which outlined a southwestwardly pitching geosyncline in which the Coal Measures of the Western Interior coal field were deposited. This geosyncline was shallow in early Pennsylvanian time and probably did not greatly exceed 700 feet in depth at the close of the Cherokee stage. At the present time, however, it is approximately 2400 feet deep at the deepest known point which is at McFarland, Kansas. An important part of the deepening is believed to have been brought about by subsidence during the post-Cherokee stages of the Pennsylvanian
