Clay Minerals at a Pennsylvanian Disconformity1

Jane A. Dalton2, Ada Swineford and J. M. Jewett
State Geological Survey, University of Kansas, Lawrence
1 Publication authorized by the Director, State Geological Survey of Kansas.
2 Present address, Humble Oil and Refining Company, Houston, Texas.

Abstract: At the Desmoinesian-Missourian disconformity in southeastern Kansas a fossil soil zone is recognized by variations in clay mineralogy in the uppermost Desmoinesian Holdenville shale, which underlies basal Missourian Hepler sandstone. The clay fraction of the overlying basal Missourian Hepler sandstone contains kaolinite, slightly hydrated illite, quartz, and vermiculite. Chlorite (rather than vermiculite) is present in shaly portions of the basal Hepler sandstone. Clay-size minerals of the typical Holdenville shale (marine) are predominantly illite, chlorite, quartz, feldspar, and a very small quantity of kaolinite. The clay-mineral assemblages in samples from the upper part of the Holdenville shale indicate hydration of illite, sporadic increase in kaolinite, possible decrease in feldspar, and progressive modification and destruction of chlorite resulting in production of mixed-layer minerals.

Clays and Clay Minerals; 1956 v. 5; no. 1; p. 242-252; DOI: 10.1346/CCMN.1956.0050120
© 1956, The Clay Minerals Society
Clay Minerals Society (www.clays.org)