376 



GEOLOGY. 



The variations in the character of the Clinton beds in different 

 localities are not without significance. In the Appalachian mountains, 

 the Clinton sediments were largely sand and mud, now in the condition 

 of sandstone and shale. In western New York and beyond, much of 

 the formation is limestone, showing that the seas of that region were 

 relatively clear, and that organic sediments predominated over clastic. 

 Bryozoan reefs, resembling coral reefs, occur in this formation in west- 

 ern New York. 1 The limestone does not mean that the water was neces- 



Fig. 173. — The Clinton formation with Niagara overlying. 



(Darton, U. S. Geol. Surv.) 



Howe's Cave, N. Y. 



sarily deep, but rather that the water in which it was deposited was so 

 nearly free from clastic sediments that the shells, etc., constituted the 

 principal part of the deposit made. Shell-bearing life may be just as 

 abundant where sand and mud are accumulating as elsewhere, but in 

 this case the product is not limestone, but sandstone, shale, etc., con- 

 taining shells. 



1 Sarle, Am. Geol., Vol. 28, p. 282, 



