CHAPTER Xr. 



THE INTERVAL BETWEEN THE EARLY AND LATE 

 WISCONSIN DRIFT. 



The Hartwell-Cuba moraine and its associated slieet of drift, and the 

 morainic tracts in the reentrant between the Scioto and Miami lobes, appear 

 to be the only outlying representatives of the early Wisconsin drift in this 

 region, the remainder of the series being concealed beneath the moraines 

 and drift sheets which are here referred to the late Wisconsin series. The 

 e\'idence of an interval between the deposition of the early Wisconsin drift 

 and the formation of the outer inoraine of the late Wisconsin series is well 

 shown in the elevated land lying between the Miami and Scioto lobes, where, 

 as above noted, the outer moraine of the Miami lobe and the outwash 

 gra^'el associated with it had been trenched by streams prior to the formation 

 of the neighboring late Wisconsin moraines of the Miami and Scioto lobes. 

 Professor Chamberlin noted this channeling and interpreted it as evidence 

 of an interval while making a reconnaissance of western Ohio in 1883, 

 and the writer gave it further attention a few years later. The cutting of 

 the broad valley of Mad River, about 2 miles in average width and 25 to 

 50 feet in depth, was referred b}- Chamberlin to this interval, as were also 

 similar channels of its tributaries. In the late Wisconsin stage the ice came 

 down about to the valley of Mad River on the west and covered the upper 

 portion of the western tributaries. The sheet of drift deposited at this 

 later advance only partially fills some of the tributaries, but its kuoUs dot 

 the slopes and bottoms of the interglacial channels, thus repeating the 

 phenomena of the early Wisconsin moraine in valleys of the Whitewater 

 system noted above (p. 306). 



On the east side of the Mad River drainage basin there are similar 

 phenomena associated with the outer late Wisconsin moraine of the Scioto 

 lobe. This moraine descends into valleys cut in the early Wisconsin drif 

 of that region. The details are given in connection with the discussion of 

 that moraine (pp. 382 et seq.). 



352 



