468 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



The ledges s(3utheast of Grarrettsville, Ohio, which exhibit strise ranging 

 from S. 65° to 86° W., do not present clear evidence that separate sets are 

 inscribed, there being numerous striae and grooves with intermediate bearings. 

 This is also the case with the striae at Hiram, Ohio, there being in the ledge 

 west of Hiram College striae at all angles from S. 40° to 62° W. 



In the above table appear several cases of cross striation which were 

 noted by the earlier observers, but which the writer has not examined. 



INNER BORDER PHENOMENA. 

 GENERAL FEATURES. 



The inner border district is limited in this discussion to the small area 

 between this morainic sj^stem and the Cleveland moraine, the latter being 

 described in a later chapter. This district is about 10 miles wide in Chau- 

 tauqua County, N. Y., and Warren and Crawford counties. Pa., and 15 to 

 25 miles in Mercer County, Pa., and Trumbull, Mahoning, and Portage 

 counties, Ohio, comprising in these covmties almost the whole area drained 

 by the Mahoning and Shenango rivers. Lying, as it does, adjacent to the 

 outer morainic system, it presents nearly as irmch variation in altitude as 

 the district covered by that system. The drift, like that in the morainic 

 system, conceals to some extent the glacial ridges and valleys in the Ohio 

 portion, but is insufficient to do so in the Pennsylvania portion because of 

 the higher elevation and consequent greater depth of the river channels, 

 though its thickness is as great as in Ohio. The drift in the valleys has 

 great range in depth, as shown by borings at Jamestown and Fentonville, 

 N. Y.; Lottsville and Corry, Pa.; French Creek Valley, near Meadville, the 

 Shenango Valley at and below Grreenville, Pa., and the Mahoning Valley at 

 Niles, Ohio. There is an average depth of over 100 feet and an occasional 

 depth of 450 to 475 feet. It seems probable that the Shenango Valley h^s 

 throughout its entire length a narrow gorge filled to a depth of 125 feet or 

 more, there being borings at Greenville, New Hamburg, Big Bend, Sharon, 

 and Newcastle, all of which have between 100 and 150 feet of drift. In 

 certain other valleys borings showing deep drift are ver}^ rare, but this does 

 not disprove the existence of channels as deep as in the Shenango, for the 

 valleys have not been adequately tested by borings. Indeed, it is probable 

 that all the large valleys have throughout much of their course nearly as 

 much filling as the Shenango. 



