GLACIAL LAKES TAYLOR, 305 



had at the same time expanded largely northeastward, and a strait 

 several miles wide had opened past the end of the ''thumb." This 

 enlarged lake, wliich is called Lake Arkona, stretched from the 

 vicinity of Gladwin, Mich., to some point at least 40 or 50 miles east 

 of Buffalo, N. Y., and covered a considerable part of southern 

 Ontario. Its outlet was westward through the Grand Kiver channel. 

 Its altitude above sea level was 694 to 710 feet. 



West and northwest of Port Huron three beach ridges form^ed by 

 this lake are known as the Arkona beaches. After they had been 

 formed the ice front made a pronounced readvance, and before it 

 halted it moved southward up the slope of the ''thumb" to Ubly. 

 This movement had no effect upon the waters in the Saginaw Valley, 

 but it raised their level OA^er the whole lake area east of the "thumb" 

 about 40 feet and submerged the entire extent of the Ai*kona beaches, 

 excepting those parts wliich lay in the Saginav/ Valley. (See lig. 3, 

 with ice border M.) 



LAKE WHITTLESEY. 



The surface of Lake Wliittlesey (fig. 3) stood about 28 feet above 

 the liighest Arkona beach ridge in the region northv/est of Port Huron 

 and 44 feet above the lowest. The ice front during this time rested 

 on the Port Huron moraine. As it advanced up the "thumb" the 

 ice v>^hich built this moraine overrode the Arkona beaches and buried 

 a considerable extent of them on the northern part of the "thumb" 

 beneath the terminal moraine or under outwash. In the southern 

 part of the Black Eiver Valley northwest of Port Huron the Arkona 

 beaches wore not ovemden, nor v/ere they buried, but they were 

 protected from the waves of Lake Wiiittlesey. Within the valley 

 they are strongly developed gravelly beach ridges, and show no modi- 

 fication due to submergence. Outside to tlie south they were almost 

 entirely washed awa,y by the storm waves of Lake Whittlesey. In 

 many places so little remains of them that tliey are traceable only 

 with much difficulty. Although they were 28 to 44 feet under the 

 water the storm v/aves swept their gravels rapidly up the slope and 

 built them into the Wliittlesey beach. The Wliittlcse}^ beach has 

 characters which indicate that it was pushed up the slope as it was 

 made, and also that it was made rapidly, for it stands very high above 

 the adjacent land and is peculiarly inde])cndcnt of to})ography, cross- 

 ing valleys of moderate depth in a direct line like a railroad embank- 

 ment. The correlatives of Lake Wluttlesey in the Saginaw and 

 ^Michigan basins arc siiown in figure 3. 



LAKE WAYNE. 



The next beach below the Arkona is the Warren. But, as was the 

 case with the Whittlesey beach, the next beach below the Warren 

 shows evidence of having been submerged and modified after it was 



