GLACIAL LAKE LUNDY AND TRANSITION TO LAKE ALGONQUIN. 405 



The various levels at which the fragments are found around Buffalo strongly suggest a 

 northward splitting like that found on the "thumb" in Michigan. The area, however, has not 

 yet been studied in sufficient detail to warrant a positive statement on this point. 



ALTITUDE AND NORTHWARD SPLITTING. 



In the area of horizontality the Grassmere beach has an altitude of 640 to 645 feet and 

 the Lundy of 615 to 620 feet. Both beaches appear to keep their horizontality farther north 

 than the beaches above them, for they appear to begin to rise about at Lexington in Sanilac 

 County or perhaps 2 or 3 miles north of this place. For 20 miles north of Lexington the rise 

 of both beaches is gradual, averaging for the upper Grassmere strand scarcely a foot to the 

 mile. West of Richniondville, where the Grassmere beach begins to split, its upper strands 

 rise more rapidly, but the Lundy continues at about the same rate. The measurements of 

 altitude on the Warren beach from Bad Axe southwest into Tuscola County were made chiefly 

 by Lane. If the isobases be laid out with reference to these measurements and projected 

 southeastward in courses parallel with those farther south they do not accord with the meas- 

 urements now available in Sanilac County. If the measurements are correct there is a marked 

 local relative depression in southeastern Huron and northern Sanilac counties — a thing that 

 seems quite improbable. 



The beach series a mile south of the north line of Sanilac County is rather remarkable. 

 Mr. Leverett made wye-level measurements in 1912 which show the following series: 



Section of beach series in north Sanilac County, Mich. 



1. A freshly cut bluff of clay and sand 46 feet high. The Nipissing and Algonquin beaches have both been cut 

 away at this locality. 



2. A sandy ridge at 626 feet and gravelly ridges at 652 and 656 feet. These three appear to belong to the Lundy. 



3. A light, broken ridge at 673 feet; a bowldery strip at 680 to 683 feet; and sandy beach ridges at 688, 699, and 

 703 feet. These ridges appear to belong to the Grassmere. The bowldery belt may be a washed-down fragment of the 

 Bay City moraine, or it may be merely the surf-wasted zone belonging to the beaches next above it. 



4. Four faint washed-down ridges at 717.4, 721, 722, and 727.5 feet. These appear to belong to the Wayne. 



5. Two closely set, weak sandy ridges at 735 and 738 feet and at the top of the series the strong, highest beach 

 ridge of this region at 752 feet. These three appear to belong to the Warren. Mr. Leverett ran a wye-level line 

 along the upper Warren ridge about N. 35° W. from this east-west line to Ruth, 4 miles distant, and found a rise of 4.5 

 feet, or to 756.5 feet. 



From these measurements it appears that the interval between the highest and lowest 

 Warren is 15 to 20 feet; from the lowest Warren to the highest Wayne, 8 to 10 feet; from the 

 highest to the lowest Wayne, about 10 feet; from the lowest Wayne to the highest Grassmere, 

 14 to 15 feet; from the highest to the lowest Grassmere, about 30 feet; from the lowest Grass- 

 mere to the highest Lundy, about 17 feet; from the highest to the lowest Lundy, 30 feet, and 

 from the lowest Lundy to the Algonquin, supposing 605 to 607 feet to be the altitude of the 

 latter, 20 to 25 feet. (See PI. XX.) 



On a line running west from Bad Axe there is a similar series of beach formations, but 

 their number and altitudes have not been accurately determined, and no continuous tracing 

 has been clone on the beaches between the Warren and the Algonquin, excepting southwest- 

 ward on two strands of the Grassmere, as noted above. Nevertheless, Lane, 1 in his report on 

 Huron County, although he had not traced any of the beaches continuously, assumes sub- 

 stantial horizontality for the Grassmere beach around the "thumb," and the same interpreta- 

 tion must necessarily be extended to the Lundy. But in reality the attitude of the beaches 

 can not be settled until the individual strands have been traced and accurate measurements of 

 their altitudes made. At present, with the Warren beach rising from 709 feet at Vassar on the 

 west side to 775 or 780 feet northeast of Bad Axe, with the Wayne beach keeping closely parallel 

 in altitude, with the upper strands of the Grassmere rising 50 or 55 feet (640 or 645 to 695 feet) 

 from the area of horizontality to the north line of Sanilac County, and with the Lundy rising 35 

 or 40 feet (615 or 620 to 655 feet) in the same interval, Lane's view that the Grassmere beach 



1 Lane, A.. C, Geological report on Huron County: Michigan Geol. Survey, vol. 7, pt. 2, 1900; chap. 4 and particularly pp. 73-74. 



