418 PLEISTOCENE OF INDIANA AND MICHIGAN. 



about 15 feet higher than the present lake. In this second eroded interval both the shale beds 

 and the old hard till are much more exposed in the bluff than they are farther south and have 

 notably retarded wave cutting. (See p. 290.) In some places the shale cliff is 10 to 15 feet high, 

 and the small stream beds in it are cut off abruptly at the cliff and are in effect hung up on the 

 present shore. The old till is almost as resistant and at Forestville forms a cliff nearly 50 feet 

 high. 



From about a quarter of a mile south of Coopers Creek the Algonquin beach may be traced 

 continuously north and west to Pointe aux Barques. Near Coopers Creek the character of the 

 shore begins to change. Instead of the heavy cutting at the modern shore with the removal of 

 the Nipissing and Algonquin beaches, the shore during and since the time of Lake Algonquin 

 has been advancing lakeward on account of the cutting down of the outlet at Port Huron. The 

 land strip remaining between the Algonquin beach and the present shore varies in width from a 

 quarter of a mile to more than a mile and is generally covered by a steplike series of beach forma- 

 tions. The shallows along the present shore are wider and more of the modern beach is on or 

 nearly on the shale. Bowlders are also more numerous along this part of the shore than farther 

 south, and all of these agencies have combined to prevent the present lake from cutting back to 

 the Algonquin beach. 



From Port Huron to Pichmondville the Algonquin beach, where not cut away, is a gravelly 

 and sandy beach ridge or series of ridges built upon low flat ground and backed by lagoons and 

 swamps. But from Coopers Creek northward it is for the most part a wave-cut shore, generally 

 a well-defined lake cliff with a gravelly beach ridge at its base and a descending series of ridges 

 with intervening bowldery floors between. The lake cliff is variable in height, generally not 

 over 20 to 30 feet, though much higher at a few places, as about a mile southeast of Huron, 

 where it is about 70 feet high. West of Huron, which is at the mouth of Willow Creek, the cliff 

 is absent for a good share of the way and is replaced by a beach ridge. At Grindstone City the 

 principal business and residence street runs along the crest of the ridge and the ground south of 

 the ridge is a trifle lower. From Huron to Pointe aux Barques the main beach is a half mile to a 

 mile back from the present shore, except for a mile southeast of Grindstone City, in which it lies 

 back less than a quarter of a mile. From Grindstone City to Pointe aux Barques the mam beach 

 is generally a ridge, but it is a bench and bluff a mile southeast of Burnt Cabin Point. 



The sandstone of the Marshall formation comes down to the level of the Algonquin beach 

 about 1J miles southeast of Grindstone City and is extensively quarried for grindstones. For 

 5 or 6 miles each way from Grindstone City, the main beach ridge is composed largely, ha some 

 places almost entirely, of disk-shaped wave-worn shingles of this rock. 



From about a mile south of Pointe aux Barques the upper Algonquin beach runs westward 

 more than 2 miles into the western part of Port Austin. It is not so strong here as usual, partly 

 because it lay at the back of wide shallows where wave action was weak, but it has the same gen- 

 eral characteristics. In the western part of Port Austin and southwestward dunes and fine sand 

 obscure the gravel ridges. 



Port Austin to Bay City. — The characters of the Algonquin beach on the west side of the 

 "thumb" differ greatly from those on the east side. Through the entire stretch from Port 

 Austin to the southern extremity of Saginaw Bay the land approaching the lake is very flat. The 

 shore faces northwest over Saginaw Bay and the prevalent strong, dry onshore winds carry the 

 sands from the shallow shore back onto the clay flats and build them into dunes or duny ridges. 

 Lagoons and swamps lie back of the upper ridge and between the later ones. Some of the ridges 

 are gravelly, the highest being most so. The mam Algonquin beach lies half a mile to a mile 

 back of the present shore and is a rather narrow duny belt as far south as Bayport. Farther 

 south it splits into several parallel ridges which spread wider apart toward Sebewamg and which 

 in places number as many as five, all having nearly the same crest height, dropping slightly 

 toward the lake, and covering a width of 1J to 2 miles. At several points between Port Austin 

 and Sebewamg exposures of gravel or gravelly sand were found in the back or higher part of the 

 Algonquin belt, and it is possible that they extend all the way but are buried under fine sand. 

 In some places the dune knolls are well developed, reaching 20 feet or so above the Algonquin 



