420 PLEISTOCENE OF INDIANA AND MICHIGAN. 



At the cemetery west of Tawas the upper Algonquin beach is a broad sandy ridge, and it 

 runs thence north passing close along the west side of Tawas Lake and turns northeast along 

 the base of the higher ground. The beach is here 4 to 5 miles from the lake and is separated 

 by a great swamp from the Nipissing beach near the shore. It is mainly a broad sandy ridge, 

 generally close to the base of a lake cliff. One or two ridges of the upper group below the highest 

 are present at some places. The lake cliff and upper ridge crosses Au Sable River 4 miles west 

 of Oscoda. 



From Au Sable River to Mullet Lake.— From Au Sable River the upper Algonquin beach 

 runs a little east of north, passing close west of the north end of Van Etten Lake. Thence it 

 runs north to the north line of Iosco County and then northeast to Greenbush. In most of this 

 interval the upper beach forms a barrier along the east side of a great swamp. Toward Green- 

 bush it becomes a belt of strong gravelly ridges. Several of the lower members of the upper 

 group are well developed here and for a mile or two south of Greenbush, this being the most 

 southerly place at which they are well displayed. 



Between Greenbush and Harrisville the highest Algonquin and the members of the upper 

 group are finely developed. The highest is generally a beach ridge at the base of a lake cliff. 

 The lower members are fragmentary in places. 



At Harrisville the upper group is well developed. The highest beach is a strong gravel ridge 

 which crosses a small ravine as a gravel bar in the northwest part of the village, but which in the 

 southwest part has a low cliff behind it. The courthouse is on the highest ridge. The even line 

 of the beach is the more prominent, because it is superposed upon an uneven morainic topography. 



The beaches below the highest are not strong, but several can be distinguished. The village 

 is spread over the whole series. One or two ridges near the lake are somewhat stronger, but 

 these appear to belong to the Battlefield or Fort Brady groups. 



A mile or two north of Harrisville the main highway follows the upper beach, which is a 

 strong ridge, rather wide and flat, backed by a cliff 20 to 50 feet high. This is the usual form of 

 the shore northward for about 20 miles. 



From Harrisville to Alcona the highest Algonquin is generally a strong gravel ridge at the 

 base of a prominent lake cliff 10 to 60 feet high. Some of the lower ridges of the upper group are 

 fairly well developed. 



From Alcona to Ossineke almost the whole slope below the highest beach is swampy. The 

 beach lies 2 to 3 miles back from the lake and the lake cliff reaches a height of 70 or 80 feet in 

 some places near Black River. (See PL XXII, B.) Great numbers of springs issue from the 

 base of the bluff and also from the slope to the lake. The road going west from Black River 

 crosses several members of the upper group of the Algonquin in a cedar swamp and ascends a 

 lake cliff about 50 feet high. 



Back of Ossineke the upper group of beaches is well developed and the old lake bluff is cut 

 sharply into high morainic ground. For 10 miles northwest from a point about 3 miles south of 

 Ossineke the bluff is high and bold. It ends abruptly about 2 miles west of the middle of Devil 

 Lake, and the beach runs on straight north for about 9 miles on a wide plain of sandy gravel. 

 At some points it is fairly well defined, but for considerable distances it is flat and sandy and its 

 exact location is difficult to determine. The ridge runs north to the bank of Thunder Bay River, 

 but seems to drop off slightly in altitude toward its north end. 



In all probability a large shallow bay extended west of this summit ridge, one arm of it 

 reaching 7 or 8 miles up the south branch of Thunder Bay River close behind the ridge. For 3 

 or 4 miles along the west side of this bay the former water level appears to be marked by a faint 

 wave-cut bench. North of the river a spit runs southwest from the main Algonquin shore to 

 meet the end of the ridge on the south side, as if to inclose completely the bay to the west. North- 

 west from this spit a faint beach inclosing a considerable swampy tract defines the irregular out- 

 line of the bay and turns up the north branch of the river. Although no shore line was found so 

 far up, it seems certain that the waters of the bay extended up the middle branch nearly to Long 

 Rapids. The summit ridge and the spit are crossed by the river about 7 miles northwest of 



