294 PLEISTOCENE OF INDIANA AND MICHIGAN. 



MAIN MORAINE OF PORT HURON MORAINIC SYSTEM. 

 DISTRIBUTION. 



In northwestern Iosco County Au Sable Kiver cuts a trench over 200 feet deep in the drift 

 deposits and at this point the main moraine of the Port Huron system is interrupted by a break 

 6 or 7 miles wide. 



South of Au Sable Kiver the moraine is spread out upon a till plain with three or four weaker 

 ridges openly deployed. It also embraces a ridge of considerable strength along the east section 

 of Rifle Kiver in eastern Ogemaw County. These ridges converge toward the great bend of Rifle 

 River in the northern part of Arenac County. The front or earliest ridge is much stronger than 

 the others. From the Au Sable it runs westward to 7 or 8 miles east of Rose City, where it turns 

 abruptly and runs directly south to a point about 4 miles west of Prescott. 



East of this and apparently next in order of formation is a weaker, irregular morainic 

 deposit which runs west for 5 miles into Ogemaw County and then turns south for 10 miles, 

 ending in a till plain without clear connection with the other ridges. 



Another slender ridge runs directly southwest for about 25 miles to the bank of Rifle River, 



2 miles west of Melita, in Clayton Township. 



From the southwest corner of Iosco County a strongly developed ridge, known locally as 

 Maple Ridge, runs more westerly to a point 3 or 4 miles east of Melita, and also eastward 5 or 6 

 miles to the Au Gres River. On the same line produced, on the west side of Rifle River, a 

 morainic ridge of moderate strength runs southwest nearly to the Arenac County line, where 

 it turns south and runs in fainter, broken form to the northwest corner of Gibson Township, 

 the northernmost township of Bay County. Another lighter till ridge starts from the bank of 

 Rifle River at the bend about 3 miles north of Sterling and runs southwest to Pine River about 



3 miles west of Sterling. Then after a break of 2 or 3 miles this ridge reappears and curves 

 southward and joins the other ridge from the north in northwest Gibson Township. Outside 

 of these ridges in the northwest part of Arenac County and neighboring parts of Ogemaw and 

 Gladwin counties is a moraine which seems to fall in the Port Huron morainic system but which 

 dies out in a sandy plain east of Tittabawassee River and is not recognized farther south. 



In eastern Gladwin County the main moraine appears to become water-laid and it begins 

 also to be largely covered with fine sand, which was blown over it, in part at least, from the 

 wide sandy plain which borders it on the west, and perhaps in part also from beaches lying 

 near its crest. Where it is water-laid, the moraine loses its relief with reference to the country 

 around it. It runs southward through eastern Gladwin County as a broad, low ridge that con- 

 trols the drainage but grows constantly less conspicuous. After entering northeastern Midland 

 County it turns gradually southeast and follows the east bank of Tittabawassee River to Sagi- 

 naw, where it ceases to be perceptible to the eye. It continues, nevertheless, in the same 

 fine along the north side of Cass River and governs the course of that stream to the vicinity 

 of Vassar, near which it again emerges from the lake bed. North of Vassar it becomes promi- 

 nent and extends directly northeast along the north bank of Cass River to the hilly interlobate 

 region southeast of Bad Axe in southern Huron County. 



In its water-laid part in the Saginaw Valley the moraine seems to be single. Five or six 

 miles north of Caro, however, it begins to show more than one line of knolls and becomes dis- 

 tinctly composite. The fiont line keeps the more direct course and passes northeastward a 

 little north of Cass City, north and northeast of which it is broken. The most prominent ridge 

 back of this turns north through eastern Elmwood Township, Tuscola County, and runs past 

 Gagetown, from which place it runs northeastward to the vicinity of Bad Axe in Huron County; 

 but from a point 3 or 4 miles northeast of Gagetown it is much weaker. Between these two 

 ridges, along Cass River in northeastern Tuscola and southern Huron counties, scattered de- 

 tached knolls and short ridges lie in a till plain, but no clearly developed moraine is visible. 



The higher irregular ground of the interlobate tract lies principally in southeast Verona 

 Township, Huron County, but partly also in northeast Bingham, western Sigel, and northwestern 

 Paris townships. 



