MICHIGAN ACADEMY OF SCIENCE. 33 



Lake Whittlesey, to the Port Huron moraine and to the Saginaw valley. 

 Briefly, the evidences and relations are as follows : 



(1) From Spring Hill southwest to the Ohio line, where they were exposed to the full 

 sweep of waves across the broadest part of Lake Whittlesey, the Arkona beaches are very 

 faint and fragmentary. They are nearly always gravelly, l)ut their relief is so slight 

 that in many parts they can scarcely be called ridges, but are merely gravel belts running 

 across the country. Usually they are not more than two to three feet high. 



But besides their low relief, these beaches show another significant 



peculiarity. -The soils which they make are not the loose, lig'ht soils 



which are generally fonnd on beach ridges. They contain a considerable 



amount of clay which acts as an agent of cementation, and makes them 



stififer and more firm than ordinary beach soils. There are several deltas 



associated with the Arkona beaches, that of the Huron river below Ypsi- 



lanti being one of the largest.- These show the same effect of stiffening 



of the soil by infiltration of clay. Both of these characters indicate 



modification by submergence. The beach ridges were almost washed away 



by the heavy seas that passed over them; their crests were lowered and 



the hollows between them and along their sides were partly filled. On 



the other hand, in times of quiet after storms the clay in the muddy 



water settled into the interstices of the gravel, making soils of the quality 



described. 



EXFLAXATIOX OF MaP. 



The accompanying map is largely diagramatic, many details being omitted. The lakes, 

 with their shore lines and outlets, were different for each position of the ice front. The map 

 may be best understood I)y noting the lake conditions associated with each of the several 

 resting places of the ice front in the order of their occurrence. 



(1) When the ice front rested on AAA, it held two lakes in front of it. In the Erie- 

 Huron basin was Lower Lake Maumee with the Lower Maumee beach as its shore line. 

 Only the northern extremity of this lake is shown on the map. Its outlet was west through 

 the Imlay channel to Early Lake Saginaw at Flushing, the outlet of the Latter lake being 

 southwest through the Grand River channel to Lake Chicago and the ^Mississippi river. 

 Faint, fragmentary beaches of this lake were found between Flushing and Maple Rapids 

 a little above the level of the Arkona beaches. 



(2) From AAA the ice front retreated to BBB. This position marks the approximate 

 place of the western ice boundary of Lake Arkona, its eastern ice boundary being in 

 western New York and probably across the west end of Lake Ontario. The Arkona beaches 

 modified bv submergence are "shown on the map, extending from the lower edge up to 

 Spring Hill and thence in full strength northward to Croswell and Applegate. Farther 

 towards the northwest they are overridden by the Port Huron moraine, passing probably 

 a little south of Ubly and" thence southwest "to Cass City. A few miles southwest of the 

 latter place they reappear in full strength running southwest to Flushing, west to Maple 

 Rapids and thence north and northwest to an interesction with the Port Huron moraine. 

 A strait several miles wide connected the waters on the east side of the thumb with 

 those west of it, where the outlet was westward through the Grand River channel. 



(3) From BBB the ice front re-advanced to CCC (the Port Huron moraine). By this 

 advance the ice closed the strait around the thumb and raised the level of the waters 

 on the east side about 45 feet. The lower right hand comer of the map shows a part of 

 Lake Whittlesev. This lake lay south of CCC with the Belmore beach as its land shore 

 to the west and Black River bay extending northward to Ulily, where the outlet river 

 passed southwest to Cass City. ^A.t this place the outlet entered Later Lake Saginaw 

 which was also held in front of the Port Huron moraine and had its outlet west through 

 the Grand River channel. The water of this lake appears to have stood at the level of the 

 lowest Arkona ridge, for no shore line representing it independently has been found. 



(4) From CCC the ice front retreated to a position not observed within the area of 

 the map, but shown conjecturally at DDD. With this movement another similar oscil- 

 lation of lake level was inaugurated, but it is not described in this paper. 



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