72 



GEOLOGY OF ERIE COUNTY 



upper Allegheny. A deep sand and gravel pit seems to mark a 

 beach or bar of this lake just south of Springville at the top of a 

 hill. It is formed of medium sized materials with well marked 

 stratification. 



' • "' ■':-...- 



F. Houghton, Photo. 



Fig. 37. Beach south of Springville, probably formed by a lake which 

 occupied the upper valley of Cattaraugus creek. 



As the ice receded, a lower pass than that at Machias was 

 uncovered at the head of the valley of the south branch of 

 Cattaraugus creek. The consequent stream flowed southward 

 over the divide at Persia at an altitude of 1300 feet and emptied 

 into the Allegheny. 



There finally came a time when the lowest edge of the 

 trough which still existed between the northward sloping land 

 and the southward facing glacier fell below the level of 1300 feet. 

 Thereupon the waters which had been escaping over the divide 

 at this level immediately overflowed at the lower levels which 



