SILURIAN EXPOSURES IN KENTUCKY 



423 





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the anticline where it crosses the upper waters of the Cumberland river, 

 in southern Kentucky. 



While passing down the Cumberland river with Professor Arthur M. 

 Miller, of the State College of Kentucky, we found two exposures of 

 Silurian rocks west of Mill Springs (figures 6 and 7). 



About a quarter of a mile up Forbush creek a small stream enters 

 from the north. Here 15i feet of Silurian limestone occur below the 

 sandy layer at the base of the Black shale. A layer with large crinoid 

 beads occurs 21 inches below the top of this limestone, and north of the 

 mouth of Forbush creek, near the 

 house of William Richardson, the 

 same layer is found, including 

 Whitfieldella cylindrical variety suh- 

 quadrata. 



At the mouth of Little Cub creek 

 the Ordovician is overlaid by Silu- 

 rian limestone, with clayey shales 

 farther up. The limestone at the 

 base is 19 feet thick. The layer 

 with large crinoid beads and Whit- 

 fieldella cylindrica, variety subquad- 

 rata, occurs 3i feet below the top 

 of this limestone. Overlying the 

 limestone are 2J feet of greenish 



clayey shale, 2 feet of clayey lime- 

 stone, and an interval of 9 feet 

 probably occupied entirely by 

 greenish clayey shale. 



At both localities the large crinoid beads belonged originally to the 

 Clinton. The Clinton was probably eroded, and the crinoid beads were 

 accumulated in the residual beds. The Whitfieldella associated in the 

 same bed is a characteristic form of the Osgood bed. It differs from the 

 typical forms of Whitfieldella cylindrica only in its more grandrangular 

 outline and its less sinuate anterior margin. The limestone below the 

 Whitfieldella layer is referred to the Clinton. The limestones and clays 

 above the crinoid bed are referred to the Osgood. The subject has been 

 more fully studied in corresponding beds in central Kentucky, east of 

 the anticline. 



Outcrops of Clinton limestone and of the Whitfieldella layer frequently 

 contain little pockets of oil in the southwestern part of Madison county, 

 Kentucky, and at various points northward. According to Professor 

 Miller, it seems that the source of the oil in Bath and Rowan counties, 



Forlrush Creek 



Figure 7. — Sections of Chattanooga Black Shale 

 and Silurian Mocks. 



Along Cumberland river, Kentucky. 



