HIGH TERRACES AND ABANDONED VALLEYS IN 

 WESTERN PENNSYLVANIA 1 



EUGENE WESLEY SHAW 



U.S. Geological Survey, Washington, D.C. 



The terraces with which this paper has to do are the well-known 

 gravel-covered rock shelves found along the Allegheny, Mononga- 

 hela, and other large streams of western Pennsylvania, about 200 

 feet above present stream channels. The abandoned parts of 

 valleys are closely associated with the terraces, being found at the 

 same elevation, and in many places the two are connected. Fig. 1 

 shows the principal areas of high terrace. The region includes all 

 the Ohio River basin above New Martinsville, where there was 

 formerly a divide. There are, however, terraces and abandoned 

 parts of valleys of the same age on the Kanawha, Guyandot, Big 

 Sandy, Kentucky, and other streams. 



The impressiveness of these features is attested by the long list 

 of names of eminent men who have studied and described parts 

 of them. This list includes Stevenson, Leslie, Jilson, Chance, 

 Wright, Chamberlin, Gilbert, I. C. White, Tight, Campbell, E. H. 

 Williams, Leverett, and others. 



Some of the earliest workers believed that the terraces were 

 due to a submergence and marine erosion. Stevenson in 1879 

 (Proc. Am. Phil. Soc, XVIII, 289-316) called attention to benches 

 along the valley of the Monongahela and its tributaries. He 

 divided them into a higher series of twenty benches, and a lower 

 one of five. The higher series he attributed to marine action. 

 They are probably entirely above those under discussion, and 

 later work on them has shown that they are obscure and are 

 probably due to hard layers of rock. The lower series of Steven- 

 son seems to include those under discussion, and he refers them to 

 stream action, without going into details of development. 



1 Published by permission of the Director of the United States Geological Survey, 

 Washington, D.C. 



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