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.
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References
Jewett, J. M., 1945, Stratigraphy of the Marmaton group, Pennsylvanian, in Kansas: Kansas Geol. Survey, Bull. 58, 148 p.
Moore, R. C., 1949, Divisions of the Pennsylvanian System in Kansas: Kansas Geol. Survey, Bull. 83, 203 p.
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Nelson, B. W., 1956, The illites from some northern Ohio shales: in Clays and clay minerals, Natl. Acad. Sci.—Natl. Res. Council Pub. 456, p. 116–124.
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Dalton, J.A., Swineford, A. & Jewett, J.M. Clay Minerals at a Pennsylvanian Disconformity. Clays Clay Miner. 5, 242–252 (1956). https://doi.org/10.1346/CCMN.1956.0050120
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DOI: https://doi.org/10.1346/CCMN.1956.0050120