NEW EVIDENCE FOR SUBSTANTIAL SHEAR IN EASTERN KANSAS; PROVIDING RELATIVE AGE CONSTRAINT FOR THE ONSET OF THE OUACHITA OROGENY

The Pennsylvanian succession of eastern Kansas and the surrounding region has undergone extensive stratigraphic analysis for well over a century. Through these studies, a general understanding of the regions stratigraphic architecture and structural provinces has developed. Of particular interest for this study is a structural high—termed the Bourbon Arch—that trends northwest from the central Kansas—Missouri state line and separates the Forest City and Cherokee basins. Unfortunately, our historical understanding of this structural high relies heavily upon studies from the 1940’s, as there exist no more recent studies that better characterize this structural feature.

Here, we provide a modern outcrop-to-subcrop analysis of the depositional architecture for upper Desmoinesian through Missourian strata spanning 29 counties in eastern Kansas. Through these data, we demonstrate that the Bourbon Arch is likely a right-lateral transpressional shear zone that has concealed the existence of a northeast-southwest trending backbulge-forebulge setting in eastern Kansas. Through these data, we demonstrate that the depocenter throughout Desmoinesian and Missourian time was to the east-southeast in Missouri; an observation that contradicts modern interpretations for the existence of a depocenter in northern Oklahoma and timing of the Ozark Uplift. In addition, these data provide precise timing of regional tectonic activity down to at least the subgroup level for the Ouachita Orogeny.