HISTORICAL REVIEW 9 



Professor Chamberlin recognized evidence of emergence between the formation 

 of this beach and the second beach, in Southeastern Wisconsin. That it 

 withdrew so much in the northern end of the Lake Michigan basin as in the 

 southern seems improbable from the evidence drawn from tilting, it being found 

 by Mr. F. B. Taylor that that portion of the basin has been uplifted more 

 than the southern. Whether this emergence is to be connected with the lake 

 stage, known as the Algonquin, is not yet ascertained, though that seems a 

 probable correlation. 



"The evidence for this emergence within the Chicago area is found in beds 

 of peaty material that occur beneath gravel of the succeeding lake stage, as 

 long since noted by Dr. Andrews and discussed in his paper cited above. In 

 Wisconsin the evidence is in clay beds, which seem to have been left in a retiring 

 water body, and which are covered by beach deposits of the succeeding lake 

 stage, as pointed out by Prof. Chamberlin in his official report of the Wisconsin 

 Geological Survey. There is need for further study of this interval in the lake 

 history before conclusions of much consequence can be drawn. 



"An excellent exposure of the structure of the bar noted above (Calumet 

 beach) is found immediately north of Evanston, where the lake is undermining 

 the bar as well as subjacent deposits. The beach sands and gravels rest upon 

 a bed of peat, which was noted by Dr. Andrews and interpreted by him to be 

 the accumulation of a marsh or partially submerged land surface. The peat 

 not only underlies the bar under discussion, but extends eastward across the 

 interval between it and the Third beach. Its level is no higher than that of the 

 Third beach, being but 12 to 15 feet above the present level of Lake Michigan. 

 The peat is in places several feet thick, but at the point where the bar comes 

 out to the lake shore it has a thickness of only 3 to 6 inches. It contains pieces 

 of mangled wood and has been disturbed by waves. Between the peat and 

 the yellowish blue till, which forms the base of the exposure, there is a gravelly 

 sand 6 to 18 inches in thickness, which appears to be a lacustrine deposit. 

 The peat is immediately overlain by about 5 feet of sand, above which there 

 is a bed of coarse gravel. The gravel is thin near the borders of the bar, but 

 has a thickness of 11 to 12 feet beneath the highest part. It is capped by a 

 thin deposit of sand and has layers of sand interstratified with it in its thickest 

 part. The presence of this gravel makes it impossible to suppose that the old 

 land surface has been buried by the drifting of material from the lower beach. 

 There seems no escape from the conclusion that the lake stood at a lower stage 

 than the level of the second beach before that beach and the bar under discus- 

 sion were formed." 



Calumet Stage {page 73) 



"Occasional reports of the discovery of a molluscan shell in this beach have 

 come to my notice, but none have been personally noted. In this respect it 

 is similar to the upper beach, and in striking contrast with the next lower beach, 

 which is full of fossils. " 



