GLACIAL LAKE ARKONA. 365 



SUBMERGED BEACHES IN BLACK RIVER VALLEY. 



The area of the Arkona beaches in the Black River valley is small, but it includes probably 

 the most remarkable evidence of readvance of the continental ice sheet and of resulting effects 

 upon lake waters to be found anywhere in the Great Lakes region or perhaps in the world. 

 It extends for about 20 miles south from Applegate and covers that part of the Arkona beaches 

 which lay in a protected position in the Black River valley while they were submerged by 

 the waters of Lake Whittlesey. 



BLACK RIVER BAY. 



The Whittlesey (Belmore) beach runs northward from Richmond in fine form and after 

 crossing Mill Creek, about a mile south of Avoca, turns east-northeast and seems to terminate 

 in a great spit at the hamlet of Spring Hill, about 2 miles northeast of Avoca. This spit is a 

 large blunt point standing about 15 feet above the surrounding plain and overlooking the 

 lower ground to the south, east, and north. It has only a narrow westward connection toward 

 Avoca, mainly along the south side of an ill-defined ridge which in some places seems slightly 

 morainic but in general seems scarcely more than an undulating part of the till plain. The 

 head of the spit, which broadens to 50 or 60 rods, is formed of gravel beach ridges built on suc- 

 cessively from the soutbwest and hooking back toward the north and west on the north side. 

 This gives the spit a bold bluff-like front facing east and north, and it was projected far enough 

 eastward from the low ground to give it similar boldness toward the south. 



Eastward from the spit at Spring Hill the road passes down a gentle slope for about 2 miles 

 to Black River and then up the western face of the main moraine of the Port Huron system for 

 about a mile, when it again reaches the level of the spit and of the Whittlesey beach. From 

 this road the narrow Black River valley stretches northward for 50 miles to the drainage divide 

 at Ubly, which is slightly below the level of the Whittlesey beach. This valley was occupied in 

 the time of Lake Whittlesey by a long, narrow bay which, except in a narrow strip on the east 

 side extending for about 20 miles north from the entrance, was less than 25 feet deep. The 

 spit at Spring Hill is a gatepost on the west side of the entrance and the gate was 3 miles wide. 

 (See fig. 5, p. 366.) 



THE THREE BEACHES. 



On the road from the spit down to the river the three Arkona beaches are crossed at right 

 angles at points where they have just turned northward up Black River valley. The upper two 

 beaches on this road are rather faint, but the lower one is fairly well developed. Southeast from 

 the road east of Spring Hill all three are very faint — are, indeed, scarcely traceable. Northward 

 from this road, however, they change within a mile to strong well-formed beaches comparable to 

 the upper Maumee beach in its best development and almost to the Whittlesey and Warren 

 beaches. They stand in most places 10 or 15 feet above their foreslopes and 4 to 10 feet or even 

 more above the plain back of them. They are gravelly beach ridges, which carry a considerable 

 proportion of sand in some places but are of clean gravel in others, and they are fairly strong and 

 continuous. The remarkable character and situation of these three beaches as they pass north 

 from this road seem to justify more detailed description. 



FIRST ARKONA BEACH. 



On the road east from Spring Hill the first Arkona beach lies three-fourths of a mile east 

 of the great Whittlesey spit and 30 to 35 feet lower. It runs a little east of north through the E. J 

 sec. 36 and across the southeast corner of sec. 25, Greenwood Township, and passes into sec. 30, 

 Grant Township. In the first mile it is weak, but it becomes strong and distinct 1£ miles east 

 of Fargo. (See PL XIII, B, p. 291.) From here it runs straight north in the western edge of 

 sees. 19 and 18, Grant Township. Here it bends west into eastern sees. 12 and 1, Greenwood 

 Township, and then northeast through sec. 6, Grant Township, into sec. 31, Worth Township. 

 Near the St. Clair-Sanilac county line a faint beach appears 8 or 10 feet above the first Arkona. 

 Its relations to the other beaches are not clear. It is described as beach A on page 369. 



