Geologic Events Affecting Geothermal Conditions in the Cherokee Basin, Southeastern Kansas: Review and Assessment

Abstract

Several methods are available to determine the maximum burial depth of sediments in basins and geothermal conditions, both past and present. Models can be constructed or past situations reconstructed by interpretative projections, geological intuition, etc. to better understand these past events (geohistory). Basin temperature modeling can be constrained and checked by such methods as reconstructed geohistory, vitrinite reflectance, T-max values, homogenization temperatures (Th) of fluid inclusions, and Apatite Fission-Track Analysis (AFTA). For the Cherokee Basin, southeastern Kansas in the U.S. Midcontinent, the maximum depth of burial of Paleozoic rocks is on the order of 6,700 feet (2050 m). Maximum burial occurred by the end of the Permian with regional subsurface paleotemperatures ranging from 75-110oC (167-2300F) and locally, temperatures up to 1500C (3020F). Later, erosion stripped off as much as 2,200 feet (670 m) of material. Circulating fluids active in lower Paleozoic aquifer systems maintain temperature anomalies of from 5 to 70C (9-130F) on oil-producing anticlines and were responsible for diagenetic changes in the sedimentary section and the hydrothermal lead and zinc deposits in the Tri-State area. Locally, temperatures may have been increased tens of degrees in the short term by small igneous intrusives in Woodson/Wilson and Riley counties implaced near the end of the Cretaceous. There is no indication that local 'hot spots' in the sedimentary section are the result of higher radioactivity in the Precambrian basement complex.