MAIN MORAINIC SYSTEM OF THE MIAMI LOBE. 365 



Just west of this exposure is a partial one in which gravel extends from 

 the creek bed up to a height of nearly 40 feet, a portion of the gravel being 

 cemented. Passing eastward, about an eighth of a mile to the place where 

 the peat comes to view, there is a nearly solid bed of till 96 feet in height 

 without the alternations of yellow and blue color seen in the western end 

 of the exposure. There is at the top of the bluff 10 to 15 feet of yellow 

 till. The remainder of the section is blue till, with the exception of occa- 

 sional pockets or thin beds of gravel, a! few inches, or at most 3 or 4 feet in 

 thickness. Between this point and the western end of the exposure there 

 are places where iiiuch gravel appears. The whole exposure is subject 

 therefore to abrupt horizontal changes, and a description which Avill apply 

 to one place may not apply to another 10 rods distant, the only constant 

 bed observed being the capping of yellow till at the top of the bluff. 



The cause of the occurrence of yellow till at several horizons is diffi- 

 cult to determine, especially since it is confined to a very small part of the 

 exposure. Possibly the till was of a yellow color when deposited. There 

 may have been four distinct ice advances, as suggested by Professor 

 Wright, each bringing in blue till, which became oxidized at the surface, 

 forming the yellow till. The occurrence of four such series or successions 

 of beds in one part of the exposure and but one series in the other may 

 perhaps be due to an accident resulting in the preservation in one place 

 and removal in another of the yellow or oxidized portions of the earlier 

 depositions. It seems quite as probable, however, that the oxidized portions 

 of the till were caused by percolating waters which followed lines where the 

 till happened to be most pervious. 



Above Germantown, along Twin Creek, there are other extensive 

 exposures of the di-ift which show in places a double series of yellow and 

 blue tills, but nowhere else within the entire district under discussion have 

 four successive series been found. 



In the case of the peat at the base of the till near Germantown, there 

 seems good reason for believing that it indicates the lapse of a considerable 

 interval of deglaciation. Whether the interval preceded the formation of the 

 early Wisconsin moraine or succeeded it remains to be determined. Orton 

 calls attention ^ to the < )ccurrence of soil at considerable depth in wells in this 

 vicinity, showing that remnants of an old buried surface are not uncommon. 



' Rept. Geol. Survey Ohio, 1869, Geology of Montgomery Co., pp. 165-167. 



