604 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



quite general, though seldom so strong as to render the water unfit for use. 

 The di-ift deposits also jaeld a shghtly saline water, the salt being obtained 

 probably from the shale fragments in the drift. 



SILT DEPOSITS BENEATH MOKAINIC DEPOSITS. 



Along several valleys in northern Ohio thei'e are heavy deposits of silt 

 beneath the till, which are of considerable interest, not only because of 

 their great amount, the depth being in places fully 200 feet, but also because 

 of their position beneath deposits of till and coarse assorted material. 

 E. W. Claypole some years ago called attention to the silts in the Cuyahoga 

 Valley in a paper entitled "The Lake age in Ohio," read before the 

 Edinburg Geological Society,^ and outlined the probable extent, in this and 

 other valleys tributary to the ' Lake Erie Basin, of lakes in which it is 

 supposed the silts were deposited. This outline was based largely upon a 

 hypothetical conception as to the position of the ice margin, the lakes being 

 considered glacial foot lakes, held between the retreating ice sheet on the 

 north and the Great Lakes-Ohio divide on the south, with outlets .across the 

 divide into the Ohio drainage system. The history of the deposition of 

 these silts proves to be more complex than the paper leaves the reader to 

 suppose, since the occurrence of morainic deposits upon their surface shows 

 clearly that they are of earlier date than these moraines. Furthermore, the 

 actual outline of the ice margin (as shown by its moraines) is so different 

 from Claypole's theoretical outline that his mapping of glacial foot lakes 

 needs revision, there being bulky moraines in the midst of the districts 

 where he supposed lakes to have been, and in which no evidence has yet 

 been recognized of deposition in lake water. The Fort Wayne and Wabash 

 moraines, in their distinct portions in northern and western Ohio, carry 

 little silt on their surfaces and are not underlain by heavy deposits of silt, 

 such as underlie the moraines of this series in the Cuyahoga Valley and 

 other valleys in the hilly district, though they cross the districts where the 

 supposed lakes were located. The geographic distribution of these silts 

 is, therefore, much more restricted than Claypole's maps indicate. On the 

 Cuyahoga Valley and in the Grand River Basin the deposits are rather 

 extensive, being 1 to 3 miles in width and 100 to 200 feet or more in depth, 

 but in Chagrin, Rocky, Black, Vermilion, Huron, and Sandusky River 



' Trans. Edinburg Geol. Society, 1887. 



