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Journal Article

Stratigraphy and Structure of the Area of Disturbed Ordovician Rocks near Kentland, Indiana

Robert R. Shrock
The American Midland Naturalist
Vol. 18, No. 4 (Jul., 1937), pp. 471-531
DOI: 10.2307/2420651
Stable URL: http://www.jstor.org/stable/2420651
Page Count: 61

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Topics: Quarries, Limestones, Shales, Fossils, Sandstones, Rocks, Fauna, Bedding, Dolomitic limestone, Quartz
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Stratigraphy and Structure of the Area of Disturbed Ordovician Rocks near Kentland, Indiana
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Abstract

This report describes a small area of greatly disturbed Ordovician rocks located about 3 miles east of Kentland, in northwestern Indiana. In the area, which is less than one-half a square mile in extent, 3 quarries reveal a 350foot sequence of dolomitic limestones, sandstones and shales ranging in age from Prairie du Chien to Utica? or Richmond? Over 100 species of fossils are reported from 3 faunal horizons of Black River age. The Rocks in the area are intensely fractured and dip steeply in numerous directions, and the jumbled fault blocks comprise an intricate fault mosaic. The uplift and consequent disruption of the strata are thought to have been produced by a violent explosion which was related to cryptovulcanism in some past geological period. The extensive glacial drift mantle conceals the rocks surrounding the disturbed area and makes it impossible to determine the time of the disruption.

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