PENNSYLVANIA AND DEPOSITS THEREIN. 



81 



Tionesta basins. When the ice-dam immediately below Emlenton 

 was finally broken there was no renewal of ponding at such an 

 elevation. 







'.^^^■■k U:av--^> -■li^'.i. 



"iz^m 



V"- -4 





r^f V-*.^^j|^ 





Fig. 15. Thinness of Leverett clay over assorted gravels, Kennerdell. 



Clarion Ponding. 



The margin of the Kansan glacier covered the mouth of Clarion 

 River. The highest elevation of overwash gravel there is 1,230 

 feet; the highest point of the thin drift is at least up to 1,400 feet. 

 In this are coal flakes carried above the outcrop, fresh fossiliferous 

 Chemung, fresh black gneiss, and completely decayed basalt. The 

 entire valley of the reconstructed Allegheny from its source to Fox- 

 burg was beneath Kansan ice. 



The sporadic deposits in this ponding vary in elevation on either 

 side of the stream at a given point, just as they do to the north. 

 Opposite Indian Hollow, on the hill at Warren, there are no gravels 

 of Kansan origin. At Tidioute there is 120 feet of difference in the 

 gravel tops ; at Foxburg, 100 feet. 



There is also a difference in the character of the gravels on oppo- 

 site sides of the stream. At Red Bank the west side shows a narrow 



