• DRIFT OF THE GRAND RIVER LOBE. 351 



SECTIOIS^ III. PROBABLK KARL,Y WISCONSIN DRIFT OF THE GRAND 



RIVER I.OBE. 



As indicated in the discussion of the drift border, a portion of tlie 

 extramorainic drift in eastern Ohio and western Peunsvh-ania, notabh' 

 that in Columbiana County, Ohio, and Beaver County, Pa., aj)pears to he 

 as recent as the early Wisconsin, while that in counties to tlie east seems 

 to be much older, Kansan or pre-Kansan in age. The poition thoug'ht to 

 be of early Wisconsin age extends only a short distance, nowhere more 

 than 10 miles, beyond the strong outer moraine of late Wisconsin age. It 

 is rarely aggregated in knf)lls or ridges, thus differing markedh' from the 

 hummocky surface of that moraine. It fills the valleys and lowlands to 

 considerable depth, but on ridg'es and hills it is represented only by scatter- 

 ing pebbles and occasional thin deposits of till. The till is often present in 

 considerable amount on the north side of ridges nearl}- to the crest, wliile 

 the south side at similar altitudes is almost destitute of drift. The till is of 

 a clayey constitution, like that of the early Wisconsin farther west. 



The chief reason for assigning this part of the extramorainic drift to 

 a later stage than the old drift farther east is found in its comparative fresh- 

 ness. It is but little more weathered than the late Wisconsin drift of the 

 neighboring moraine. A response with acid can usually be obtained at a 

 depth of but 5 or 6 feet The bowlders also are but little more weathered 

 than those on the surface of the late Wisconsin moraine. They are strik- 

 ingly in contrast with the rotten and deeply weathered bowlders and 

 pebbles which characterize the old drift, of northwestern Pennsylvania. 



The grounds for sejjaratiug this extramorainic drift from the late Wis- 

 consin are perhaps open to question. It has impressed the writer, and also 

 Professor Chamberlin, as somewhat more weathered than that of the neigh- 

 boring late Wisconsin moraines. The fact that it is so strikingly different 

 in topography has also been considered a matter of some consequence. It 

 also seems natural that this lobe, as well as the Scioto and Miami lobes, should 

 have extended farther in the early Wisconsin than in the late Wisconsin 

 stage. But the reference to the early Wisconsin is only provisional. This 

 drift may yet prove to be the product of an advance but little earlier than 

 tha,t whicli formed the bulky late Wisconsin moraine. 



