316 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



of blue till, which is here exposed to a depth of 35 feet without reaching its 

 base. In the blue till are thin horizontal beds of sand of slight extent. 

 Near the western end of the same railway cutting and toward the top of 

 the bank there is a slight exposure of beds of gravel which are disturbed 

 and shoved into a nearl}' vertical position. The blue till beneath these 

 beds is also disturbed t(j a slight depth, as if by a vigorous shove from the 

 west. This disturbance of the beds is readily attribjiitable to the movement 

 of the ice sheet across them. It is probable, though as yet scarcely dem- 

 onstrable, that the Wisconsin drift includes only the upper yellow and blue 

 till sheets. 



About 3 miles north of Xenia, on the south bluff of the Little Miami 

 River, is a sharp di-ift knoll about 40 feet in height, which has been opened 

 from top to bottom; indeed, the excavation goes about 15 feet below the 

 base of the knoll. The knoll is made up almost entirely of gravel, and this 

 gravel, especially in the central and southern parts, has a decided southward 

 dip of 20° to 30° or more. At the level of the base of the knoll the gravel 

 suddenly ceases and below it there is a level-topjjed yellow till with weath- 

 ered and leached surface, which appears to be a buried soil or old land 

 surface upon which the knoll was deposited. The gravel being Wisconsin, 

 the till and underljning deposits are referred with some confidence to pre- 

 Wisconsin time. The till has a thickness of about 10 feet. Beneath it are 

 sand and g-ravel beds in arching and (_)blique attitudes. A chain of knolls 

 leads westward from this gravel knoll along the north border of the gravel 

 plain locally known as "Cherry Bottoms," and then southward along its 

 west side, constituting the outer border of the moraine, but no other knolls 

 have been opened s^ifficiently to show their structure. 



No records have been obtained of deep wells in Greene and Warren 

 counties, Ohio, except at the Lebanon gas well, where the drift has a thick- 

 ness of 126 feet. The drift is usually not thick, if we may judge by the 

 altitude of rock outcrops along streams. Probably the average thickness 

 on uplands in these two counties is less than 50 feet. 



At the time of a visit to Turtle Creek Valley, in September, 1891, the 

 grading for a new railwaj^ was in progress. The grading begins near the 

 point where the moraine touches the Little Miami gravel plain and passes 

 northward, showing the structure of the drift to a depth of several feet. 

 There is a slight capping of silt or earthy deposit on the outer face of the 



