298 - PLEISTOCENE OF INDIANA AND MICHIGAN. 



and thus making it impossible to learn anything definite about the relation of these beaches to 

 the main moraine in this locality. 



More or less outwash issued directly from the ice along its front, but no notable deposit is 

 known with certainty, except in Sanilac County, where a thin, narrow sheet of sandy outwash 

 spreads like an apron from the front of the moraine from Amadore northward nearly to the 

 Huron County line. Although this deposit is relatively small and narrow, its southern part 

 buried two of the beaches of Lake Arkona. 



The total absence of outwash along some parts of the moraine front is more remarkable 

 than its presence in other places. From a mile west of Amadore southward to the junction of 

 Mill Creek with Black River, no outwash whatever is visible, and the condition of fragments of 

 the lower Arkona beach, which lie in actual contact with the base of the front slope of the 

 moraine, proves conclusively that none was ever deposited. 



GLACIAL DRAINAGE. 



UBLY CHANNEL. 



While the ice front was resting on the main moraine of the Port Huron system the Huron- 

 Erie basin was occupied by Lake Whittlesey. The lake discharged through a long, narrow bay, 

 called Black River Bay, which extended from a 3-mile entrance between Spring Hill and Zion, 

 14 miles northwest of Port Huron, northward for 50 miles, nearly to Ubly. From a swamp at 

 the head of this bay the outlet ran close along the ice front in the reentrant angle on the "thumb," 

 and the channel now marking its course lies close along the front of the moraine from 3 miles east 

 of Ubly to Cass City, about 18 miles on the course of the channel, where it enters Lake Saginaw. 



The Ubly channel is short, but it is one of the large, important channels of the Great Lakes 

 region. Its head is 3 miles east of Ubly, in a swamp whose waters flow northwest to the North 

 Branch of Cass River. Two miles southeast of the divide at the head of the channel the swamp 

 is less than a mile wide, but on the divide its width is about 2 miles and it continues with this 

 width to the bend of Cass River in sec. 15, Bingham Township. Here the channel turns 

 sharply southwest through a passage not over three-fourths of a mile wide and continues thence 

 past Ubly to Cass City with a width of 1 to 1^ miles. 



A high till ridge just east of Ubly separates it from the head of the channel at the divide. 

 On the west side of this ridge another narrower passage, floored with sandstone in nearly hori- 

 zontal beds, runs northwest from the Black River swamp a mile or two southeast of Tyre and 

 once carried a large body of water to the main channel at Ubly. Tyre stands on the floor 

 of this branch channel. 



The floor of the Ubly channel shows more pronounced evidences of scour by a large river 

 than do most of the glacial channels. Comparatively little of it is swampy, this character being 

 confined mainly to its upper and lower reaches. The rest of it is floored with immense numbers 

 of bowlders and at places with pebbly or gravelly bars, some of them 8 or 10 feet high, whose 

 shapes show distinctly that they were produced by a strong current flowing southwest. 



At Holbrook, in northeast Greenleaf Township, a passage opens into another channel lying 

 close south of the Ubly. 



Cass City is built on a gravelly terrace which appears to be partly the product of a glacial 

 stream coming from the northwest through the moraine and partly a delta deposit of the Ubly 

 outlet river. 



The present altitude of the floor of the channel is about S00 feet at its head and about 740 feet 

 a mde or two east of Cass City. The channel lies nearly in the direction of maximum uplift, 

 about N. 22° E., and runs almost directly down the slope of the tilted land. From its present 

 fall of nearly 60 feet it is necessary therefore to subtract 15 or 16 feet in order to find its original 

 descent of 40 to 45 feet. This original descent is the difference in the altitudes of Lakes Whit- 

 tlesey and Saginaw and indicates the amount that the Huron-Erie waters were raised by the 

 readvance of the ice front to the front ridge of the Port Huron morainic system. 



