Preliminary Study of the Structure of Western Kansas

Abstract

Structure maps of the Stone Corral and Dakota formations show regional dip toward the north but are discordant in many respects. The thickness map of the interval between them reveals the structure of the Stone Corral when the Dakota was still undisturbed. The difference between the structure of the Stone Corral and the Dakota is due to the fact that the structure of the Stone Corral was already well defined before the development of conflicting post-Dakota deformation. The Stone Corral-Dakota thickness map shows that at the end of Dakota time, the structure of the Stone Corral formation conformed to the pattern of deformation that produced the Hugoton embayment of the Anadarko basin. This thickness map also reveals that there was, at the end of Dakota time, a northerly trending anticline (Oakley anticline) with structural relief of more than 200 feet at the top of the Stone Corral. Arching of the Central Kansas uplift was inactive after Stone Corral time and probably for some time before, but secondary structures continued to develop on its crest even after Dakota time. Except as reflected by the western limb of the Hugoton embayment, the northeasterly dip on the flank of the Las Animas arch was accentuated in Kansas after Dakota time and was in the main a postCretaceous structural feature in Kansas.

Post-Dakota deformation resulted in a generally northerly dip of the rocks of the region and introduced new regional structural features. These movements reinforced some of the older regional features, modified all in varying degree, and destroyed some broad pre-Cretaceous structural features at the horizon of the Stone Corral. The Oakley anticline was cancelled out at this horizon by a post-Dakota syncline, and the steeper anticlinal structure of the Oakley anticline in older rocks was modified but not destroyed. In a large part of the area east of the Las Animas arch, the low post-Dakota northerly dip did not materially alter the relation of anticlines at the horizon of the Stone Corral to the steeper structures of the older rocks.

A thickness map and cross sections of the Morrison formation reveal topographic relief at its top and bottom and suggest a low dip toward the Denver basin at the close of Morrison deposition. A thickness map of the interval between the base of the Cretaceous and the top of the Dakota reveals pre-Cretaceous topographic relief of more than 400 feet. An east-west cross section shows the bifurcation of the Stone Corral in southwestern Kansas. A north-south cross section shows that post-Permian movements tilted the Stone Corral formation toward the north but failed to overcome the original southerly dip of deeper beds whose dip was reduced by the amount of the post-Dakota northerly dip.