66 GEOLOGY OF ERIE COUNTY 



present valley before glacial time and Buffalo creek is the 

 dwindled successor of a river which during Mesozoic time 

 carved a wide valley through the soft Portage and Marcellus 

 shales of Krie county. The great lake at our doors probably did 

 not exist at that time. If it were in its present location it was 

 at least different in its aspect. Probably its present bed was the 

 valley of a great river which received the waters of what is now 

 the upper Allegheny river and carried them northwards to the 

 valley where is now and perhaps then was the great Lake 

 Ontario. On the south the hills, our hills, of Erie county reared 

 their heads as now. The " Ledge" looked then much as it does 

 to-day. 



F. Houghton, Photo. 



FlG. 35. Valley of Cattaraugus creek below Springville. This was eroded 

 before the Glacial Age, perhaps in Mesozoic time. 



Although the main features of the county remain as they 

 were in the Mesozoic, they have been changed in detail. Ages 

 of erosion have flattened the hills and widened and deepened the 

 valleys. These hills and valleys were later buried from sight for 

 countless ages under a great ice sheet and when they finally 

 emerged from their icy prison they were everywhere mantled and 

 clogged with the debris of glaciation. Our gorges and falls are 

 the result of new valley-cutting by streams whose old valleys, 

 widened and flattened through long eras of erosion, had been 

 dammed and filled with drift. Even our great Lake Erie is but 

 the dwindled successor to the greater bodies of icy water derived 

 from the melting away of the ice sheet. 



The glacier which so changed the topography of our county 

 was the southern extension of an immense continental ice sheet 



