PRELIMINARY SUBSURFACE MAPS OF LOWER-MIDDLE MISSISSIPPIAN STRATA IN SOUTHWESTERN AND SOUTH-CENTRAL KANSAS

This study, conducted as part of the USGS STATEMAP Program, produced three geologic maps (scale 1:270,000) depicting the top of the Kinderhookian, Osagian, and Meramecian stages in southwestern and south-central Kansas, between the Central Kansas Uplift and the Hugoton Embayment of the Anadarko basin. These maps, created using ArcGIS and formation top data from the Kansas Geological Survey public database, build upon previous structural contour maps from Kansas as well as Colorado and Oklahoma used to assist with identification of regional trends beyond Kansas. During the Mississippian, shallow seas deposited limestone and dolomite, forming key stratigraphic units: the Kinderhookian’s Gilmore City Limestone (GLC), the Osagian’s Keokuk-Burlington Limestone (KBL), and the Meramecian’s St. Louis Limestone (SLL) in Kansas. The GCL consists of noncherty, soft, chalky fossiliferous limestone, with oolitic and chert-bearing variations in western Kansas, and is separated from overlying Osagian rocks by an unconformity. The KBL is characterized by cherty, siliceous, dolomitic limestone and is typically unconformably overlain by Meramecian rocks, though this disconformity is less distinct in southwestern Kansas. The SLL comprises predominantly noncherty limestone, with widespread areas of oolitic limestone and calcarenite. In the Hugoton embayment, the SLL includes coarse-grained fossiliferous dolomitic limestone, with localized occurrences of chert, limestone breccias, and anhydrite. Meramecian rocks are generally conformably overlain by Chesteran rocks. Bedrock depths in the study area range from -1,200 to -5,000 ft, with shallower depths in the north and west transitioning to deeper depths in the south. These maps provide valuable insights into the region’s subsurface geology, aiding in resource exploration (e.g., the Mississippian Lime play) and potential CO₂ storage initiatives.