330 W. UPHAM — PREGLACIAL AND POSTGLACIAL VALLEYS. 



area, named b}^ Logan and Newberr}^ the " Erie clay," corresponds fully 

 with the upper part, to about the same depth, of the smooth exi)anses of 

 till within the areas of the glacial lakes Minnesota and Agassiz, held by 

 the waning ice barrier respectively in the basins of the Minnesota river 

 and the Red river of the North. 



DELTA OF MODIFIED DRIFT AND ALLUVIUM. 



Flowing from a reentrant angle of the departing ice-sheet, shown by 

 the course of its retreatal moraines as traced by INIr Frank Leverett. the 

 head stream of the Cuyahoga river received a large tribute of modified 

 drift, some of which was soon laid down as gravel and sand along the 

 valley, while the fine sand and cla}^ were borne forward to the Western 

 Erie glacial lake, standing about 200 feet above the present lake level, and 

 especially to the ensuing lake Warren, which held in succession three 

 lower levels. With the modified drift, sup])lied directly from the ice 

 melting, tins river and its tributaries brought also much alluvium eroded 

 from their channels and washed from the general surface of the drift 

 sheet. 



Only scanty delta deposits are found to have been made contempo- 

 raneous with the Leipsic beach, which was formed by the ^^^cstern Erie 

 lake. During the time of that beach the Cuj^ahoga river i)robably de- 

 posited nearly all its modified drift and alluvium along its valle}^ which 

 appears to have required the greater ])art of that time to become filled 

 along its south to north portion up to the Leipsic water level. Certain 

 gravel and sand beds, however, underlain and overlain by till and strati- 

 fied clay between the Forest City park and East Clark avenue, to be de- 

 scribed later in detail, appear to be sublacustrine delta beds of Leipsic 

 age. 



Contemporaneous with the formation of the Belmore or first beach of 

 lake Warren, an extensive tract of fine gravel and sand was spread in the 

 lake ui)on the southern half of the site of Cleveland. At tliis time the 

 Cuyahoga drainage basin was clad with a coniferous forest, from which 

 trunks and branches of cedar, s})ruce, and ])inc, as determined by ^Vhit- 

 tlesey and Newberry, were swept by the river floods out into the lake, 

 sinking waterlogged to the lake bed of till three to five miles beyond the 

 mouth of the river as it was during that stage of the glacial lake, where 

 now they are encountered at the base of the later delta sand in the northern 

 part of the city. 



During the stages of lake Warren marked by the lower Woodland 

 Avenue and Euclid Avenue beaches, the deposition of the delta continued, 

 its sand and silt being then wholly alluvium, sui)})lied by the ordinary 



