Hydrogeology of the Codell Sandstone Member, Carlile Shale (Upper Cretaceous), in Western Kansas

The Codell Sandstone Member of the Carlile Shale is located in the northwest quarter of Kansas. As a source of groundwater, it is most frequently utilized in Ellis, Trego, Rooks, Graham, Gove and Logan counties. The aquifer is characterized by two facies. Both the King Hill facies and the Antonino facies are made up of an argillaceous sandstone interbedded with siltstones and limestones. The King Hill facies averages 30 feet (9.1 meters) in thickness and the Antonino facies averages less than 5 feet (1.5 meters). The potentiometric surface of the aquifer indicates a west -to-east groundwater-flow direction. Water quality of the Codell aquifer is very similar to the Ogallala Aquifer with differences in silica and bicarbonate concentrations. The source of groundwater recharge to the Codell aquifer is from groundwater which migrates down through the joints in the overlying Fort Hays Limestone and Smoky Hill Chalk from three major sources: 1) the Ogallala Aquifer, 2) alluvium in the major drainage systems, or, 3) direct precipitation on the exposed Fort Hays Limestone and Smoky Hill Chalk. The Codell aquifer has a low range of transmissivity and specific yield due to the abundant matrix clay in the sandstone.