Chemical and Petrographic Studies of the Fort Hays Chalk in Kansas

Abstract

The chemical composition, petrographic character, and commercial usefulness of the Fort Hays chalk of Kansas are described in this report. The Fort Hays is the lower member of the Niobrara formation of Cretaceous age and crops out extensively in the north-central and central western part of the State. Samples were collected from Jewell, Smith, Osborne, Rooks, Ellis, Trego, Ness, Lane, Finney, and Hamilton counties. Results of chemical and petrographic analyses show that the Fort Hays chalk is composed of fine-grained calcium carbonate except for scattered megafossils and limonite concretions. The average calcium carbonate content (excluding basal samples) is 94.2 percent, ranging from 98.2 percent to 88.7 percent. The grain size and, the average calcium carbonate content did not vary significantly over the area studied. The chemical and petrographic properties compare favorably with whiting specifications for the paint, putty, rubber, and chemical industries.