Chattanooga Shale in Kentucky. 123 



the wagon road, the lowest strata of the black shale lie in shal- 

 low, irregularly eroded pockets in the limestone. In some of 

 these a thin layer of reddish clay was observed between the 

 limestone and the undisturbed black shale. 



In the southwestern part of the black shale area of outcrop 

 near Rileys station in Marion county, unconformity at the base 

 of the shale is well exposed in a small ravine a few hundred 

 yards northwest of the railroad station. Here the hollows in 

 the limestone under the black shale are deeply filled with dull 

 red residuary clay, while but a thin band of the clay covers the 

 intervening elevated ridges in the limestone. The upper sur- 

 face of the latter is extremely uneven and seldom conforms 

 with the approximately parallel bedding planes in the lime- 

 stone. The unconformity as it is seen here is illustrated by 



Fig. 1. 



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B 



gnus 



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m= ^icgsi 



-ifl- 





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i ( r 5 ^ 



*"1 Vaster** 1 1 1 









=5=^^ . J-V^ 1 1 | ^ i < 



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W i 





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&n- ' i ' 





II 1 1 1 





1 1 1 1 II II 111 1 1 1 1 1 1 I 



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1 



Fig. 1. Section at Rileys, Kentucky, showing irregular surface of Devo- 

 nian limestone and residuary clay beneath the Chattanooga shale. A Devo- 

 nian limestone, B residuary clay, C Chattanooga shale. 



tig. 1. The maximum thickness of the residuary clay which 

 has been observed at the base of the black shale occurs in Mad- 

 ison County, southwest of Berea, near the head of the west 

 fork of Rocky Branch. The clay has a thickness in places of 

 3 feet or more at this locality. It is a brown clay containing 

 numerous fragments of the chert which characterizes the under- 

 lying Devonian limestone on Bocky Branch. The clay lies at 

 this locality in deeply excavated troughs and pot-like depres- 

 sions in the limestone. The upper part of this clay shows indi- 

 cations of having been reworked. One or more thin papery 

 bands of shale show a superposed bed of clay. 



The place usually occupied by the residuary clay which has 

 been described is sometimes tilled on the eastern side of the 

 Cincinnati geanticline by a limonite ore. The iron ore has 

 been found in the form of small lenticular and widely sepa- 

 rated masses over a line of outcrop nearly 150 miles in length, 

 extending through Boyle, Lincoln, Montgomery, and Casey 

 counties as far north as Peebles, Ohio. This ore was exten- 

 sively worked at one time near Preston, Ky., where the bed 

 is said to have had a thickness of from 7 to 15 feet. 



