8 MORRIS M. LEIQHTON 



ville ice may have removed the leached zone, as the contact of the loess with 

 the Shelbyville till is sharp. 



The "2-inch layer of humus which occurs 10 inches below the top of the 

 loess records a cessation of wind deposition. Inasmuch as the writer d 

 not recall any other exposure of Peorian loess — among the hundreds which 

 he has seen — which shows a definite soil zone within the loess, he is inclined 

 to the view that the soil represents the latter part of the Peorian epoch, and 

 that the overlying 10 inches of loess was deposited during the oncoming of 

 the Shelbyville ice. The alternative view is that this soil occurs within the 

 body of the Peorian loess, recording two subepochs of loess deposition in 

 the Peorian epoch, in which case there is the possibility that if there were 

 a leached zone of the loess before the invasion of the early Wisconsin ice, 

 that this zone and a part of the calcareous zone were removed by the ice. 

 In a recent report on "The Iowan Drift — a Review of the Evidences of the 

 Iowan Stage of Glaciation," Alden and Leighton present the view that the 

 great body of loess associated with the Iowan drift was deposited aim 

 immediately following the recession of the Iowan ice sheet, but under sufri- 

 cientlv favorable climatic conditions to destroy the glacier and to permit the 

 growth of vegetation and the existence of herbivorous snails;' in other 

 words, the time of the loess deposition was referred to the early Peorian 

 epoch. 



If the first view outlined above is correct, the time of the deposition 

 of the loess in the Farm Creek exposure is more closely connected with the 

 Wisconsin glacial epoch than if the second view were found to be true. On 

 the other hand, it is clear that the Peorian loess was deposited a long time 

 after the deposition of the Illinoian drift. 



4. The body of till at horizon (i is unquestionably Early Wisconsin, in 

 age, and is clearly Shelbyville, since the Bloomington moraine lies to me 

 north of this locality. 



."">. The overlying gravel is probably outwash from the Bloomingt n 

 ice, since it occurs above the till and has an elevation in accord with the 

 Bloomington outwash at Peoria. 



(i. The loess above the Shelbyville till and the Bloomington gravel is 

 not mentioned in the legend accompanying the photograph in Monograph 

 XXXVIII previously cited. Its thickness is from A]\ to ', feet. The up] 

 ■iy 2 to 5 feet, including the soil, is non-calcareous, and where the non-cal- 

 careous portion rests on gravel, the gravel is partly leached. But where 

 the loess is thicker than 5 feet its base is calcareous and the gravel hem 

 is unleached. This shows that at least a part, if not all. of the loess v 

 deposited in a calcareous state immediately after the retreat of the ice at a 



> loica lit 1,1. Survey, Vol. XXVI, ••Annual Report for 1915," pp. 156-58. 



