GLACIAL LAKE ALGONQUIN. 417 



below the beach ridge, and the dunes rise considerably higher. From Gardendale the depression 

 runs southeast, narrows to one-quarter of a mile in width, and ceases to be swampy. McNeils 

 Creek comes from the higher ground west of Gardendale and flows southeast through the swampy 

 lagoon nearly to Port Huron before it breaks through the ridges. Near Port Huron the lagoon 

 passes into the northern part of the city as a clay fiat with more or less thin sand upon it and lies 

 very little below the crest of the main ridge. 



From the north end of the swamp to a point a mile south of Lakeport a well-defined, though 

 rather faint shore line skirts the western border of the swamp at the same level as the main 

 Algonquin ridge. Gardendale is on the northern extremity of an extensive sandy, gravelly 

 deposit, apparently a thin-spread delta built into the shallow margin of Lakes Lundy and Algon- 

 quin. Tliis delta overspreads the clay plain on both sides of Black River and slopes gently east- 

 ward and northward to the edge of the swamp. The faint beach along the west side of the marsh 

 turns southeast at Gardendale and runs along the edge of the delta, forming for 2 miles or more 

 a low but well-defined ridge, which descends steeply 5 or 6 feet to the swamp in front. 

 The Pere Marquette Railroad runs on this ridge or just behind it for 2 miles southeast from 

 Gardendale. 



From its faintness in some places this back beach might be regarded as affording no certain 

 evidence of wave action. But such action appears to have controlled the course of at least one 

 line of drainage, carrying shore drift south athwart the course of Black River in such amount as 

 to turn the course of that stream back of the beach at Huronia from east to south. 



The back beach skirts the western side of the swamp very closely and is relatively imma- 

 ture when compared with the main ridge. From its position behind the main ridge, it is plain 

 that this beach was made before the main ridge, the latter having been built southward across 

 the shallows at a later time. The position and relations of the main ridge indicate that from 

 Lakeport south it is a spit built mainly by shore drift from the north although probably in part 

 also from material swept up from the pebbly clay bottom immechately in front. 



From Stevens Landing for nearly 15 miles north the present lake has cut heavily into the 

 land, the Algonquin beach has been entirely removed, and the present lake is now cutting back 

 at a rapid rate. The lake cliff is mainly clay and is 25 to 40 feet high and vertical. At some 

 places there is no room to walk at the base unless the lake is low and very quiet. In recent years 

 the shore between Stevens Landing and Lexington has been retreating about 6 feet per year and 

 in some places in Huron County (according to Lane) as much as a rod a year. 1 About a mile 

 north of Stevens Landing the recent cutting has taken away a large part of a farm, compelling 

 the removal of farm buildings and undermining an apple orchard. In 1904 some trees had just 

 fallen and others had fallen two or three years before. 



The exposure along the face of the cliff showed several beds of clay and some sand and sandy 

 clay in the upper part, all horizontally bedded and overlying brownish-gray till containing some 

 stones. In several stretches between Lexington and Harbor Beach older pre- Wisconsin till is 

 exposed on the shore and extends below lake level. Five or six miles south of Port Sanilac 

 the cliff has cut back into the sands of the Lundy beach, forming a bluff 40 to 45 feet high. 



About a mile south of Port Sanilac, where the present shore bends a little eastward and the 

 bluff grows lower, the Algonquin beach reappears and continues north for about 11 miles, or to 

 within a mile of Richmondville. For most of the distance it consists of two or three sandy 

 gravel ridges, largely covered near Forester by fine sand and small dunes. 



The jDreservation of this stretch of the beach is probably due in part to exposures of shale 

 along the present shore and in part to exposures of the old indurated till, both formations resist- 

 ing wave erosion more effectively than the later unconsolidated clay and sandy beds. 



From about a mile south of Richmondville for about 15 miles northward to a point a little 

 south of Coopers Creek (5J miles south of Harbor Beach) the Algonquin beach is entirely cut 

 away. In the southern part of this interval it is cut away by the present lake, but north of a 

 point 2 or 3 miles south of Coopers Creek it was removed by Lake Nipissmg, which stood 



1 Lane, A. C, Summary of surface geology of Michigan: Ann. Rept. Michigan Geol. Survey for 1907, 1908, p. 135 and PI. VIII. 

 34407°— 15 27 



