GLACIAL LAKE ALGONQUIN. 425 



Skull Cave. Several weaker ridges appear among the stronger ones on the short target range. 

 (See PL XXII, A, p. 420.) 



The ancient island — the part which was an island at the time of Lake Algonquin — rises about 

 SO feet above the upper beach and is about three-quarters of a mile long from northwest to 

 southeast. It is roughly triangular in shape, tapering to a sharp point both at the north and 

 the southeast. The entire upper group of Algonquin beaches is crowded close together on 

 its south side and is spread out to a width of over a mile on its west side. On the east side 

 the island was heavily eroded at one of the lower levels of the upper Algonquin group (appar- 

 ently the level of the fourth or fifth strong beach below the highest), being deeply cut into 

 a cliff 70 to 80 feet high and three-quarters of a mile long. (See PL XXIX, A, p. 453.) One 

 or two of the strong ridges run along the outer edge of the beach made at this time. The cliff 

 is largely composed of brecciated and recemented limestone with a few feet of stony till at the 

 top. Near where they start away from this cliff all the beaches are uncommonly coarse in their 

 composition, even including bowlders of considerable size, but toward the west, as seen in the 

 gravel pit just west of the cemeteries, the gravel grows much finer and the pebbles well 

 rounded. 



Neither Round nor Bois Blanc islands were high enough to record any of the upper Algon- 

 quin group. The high ground south of St. Ignace barely reached the lowest of the upper group, 

 but Gros Cap, 4 miles west of St. Ignace, is higher and two or three of the lower members 

 occur on it. Three to four miles north of Hessel two or three islands in Lake Algonquin show 

 the whole upper group well developed on their flanks. These have been called the Munuscong 

 Islands and were described by the writer 1 and more recently by Russell. 2 



Beaver Island. — In the south part of Beaver Island, which lies in the northern part of Lake 

 Michigan 30 to 40 miles northwest of Charlevoix, a morainic tract about 4 miles long from north- 

 east to southwest and \\ miles wide rises considerably above the highest Algonquin beach. On 

 the north, west, and south sides of this ancient island the Algonquin beaches have been explored 

 in part and all of them are unusually well developed. High Island, 4 miles west of Beaver 

 Island, records several of the lower ridges of the upper group but apparently not the highest. 

 None of the other islands of that group rise to the Algonquin level. 



Petoskey to Traverse City. — In the east part of Petoskey the bluff disappears and the upper 

 beach takes the form of an ill-defined terrace in passing through the town. But near Bear 

 Creek in the southwest part a strong barrier ridge of coarse gravel spans the narrow valley 

 of the creek, except where the stream passes through, and runs on westward less than a mile 

 from the present shore. The level of Lake Algonquin probably extended several miles up 

 this valley. A mile or two west of Petoskey the upper beach again takes the form of a wave- 

 cut bench and lake bluff for about 7 miles. About 5 miles out it crosses the valley of Bear 

 Lake as a heavy barrier ridge close to the north end of the lake. But Bear Creek, which is the 

 outlet, passes out of the southeast end of the lake and flows north about 8 miles before reaching 

 the bay. 



South of Bay Shore, 2 miles west of the north end of Bear Lake, another depression run- 

 ning south to Hortons Bay on Pine Lake is crossed bj r a fine barrier ridge which rises 25 or 

 30 feet above the trough back of it. The depression is rather narrow at its north end and 

 the barrier curves sharply north on the west side. For the next 2 or 3 miles to the west the 

 beach lies a mile north of the highway and is largely on bedrock; it is not very strong and 

 its materials are mainly shingles and slabs of limestone. At Burgess it grows stronger and 

 runs south on the east side of Susan Lake. On the west side of this lake the remnant of a 

 drumlin has a well-formed beach on its west side, and from this a fine barrier bar of gravel 

 runs more than a mile southeast around the south end of Susan Lake. 



The waters of Lake Algonquin extended up the valley of Pine Lake to Boyne Falls and 7 

 or 8 miles up the valley of Jordan River to a shallow divide south of Finkton, beyond which 

 small streams flow northwest to Intermediate Lake. The lake waters crossed another low 

 divide extending west from the south arm of Pine Lake to the north end of Intermediate Lake 



1 Taylor, F. B., The Munuscong Islands: Am. Geologist, vol. 15, 1895, pp. 24-33. 



2 Russell, I. C, A geological reconnaissance along the north shore of Lakes Huron and Michigan: Ann. Rept. Michigan Geol. Survey for 

 1904-5, p. 85. 



