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This paper summarizes the subsurface occurrence of the Kinderhook-New Albany succession in Illinois and shows the relationships of the formations and facies from place to place.
A zone of relatively thinner strata extending northeasterly from the Ozark uplift divides the region into two sedimentary provinces. Southeast of this zone the succession is predominantly hard, black New Albany shale capped by the Rockford limestone. Its thickness increases southeasterly to a maximum in Gallatin and Hardin counties. Along the zone of relatively thinner strata the black shale is overlain by gray and greenish shales and siltstones in turn overlain by the Rockford limestone. In a limited area northwest of the zone, as far as Calhoun, Green, Macoupin, and Montgomery counties, the upward succession is the black Grassy Creek shale, the Louisiana limestone, the blue Maple Mill shale and siltstone, and the Chouteau limestone. The Chouteau limestone is shown to be the westerly equivalent of the Rockford limestone.
Farther northwest, as far as the Kinderhook occurs in Illinois, the black shale grades upward through grayish brown into gray and blue shales, succeeded by the English River siltstone, the McCraney limestone, and the Prospect Hill siltstone. The total thickness of these strata reaches a maximum in Hancock County.
There is an erosional unconformity between the Kinderhook and overlying Osage group.
A number of cross sections and isopach maps illustrate correlations and changes in thickness and facies of the strata throughout their subsurface occurrence in Illinois.
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