GEOLOGY OF THE PORT LEYDEN QUADRANGLE 4.T 



Near Partridgeville the Precambric lies at about 1300 feet above 

 the sea level, while at Hawkinsville (Boonville sheet), 16 miles 

 southward, it lies at 1060 feet. The difference in elevation is 240 

 feet or the slope per mile southward is 15 feet between these places. 



One mile south of Donnattsburg the Precambric is at 1020 feet, 

 while at Port Leyden, 10^ miles southward, its elevation is 900 

 feet. The difiference in elevation of 120 feet shows a southward 

 slope of over 11 feet per mile in this direction. 



The Precambric near Partridgeville is at 1300 feet, while just west 

 of Glenfield, 7^ miles westward, it lies at 840 feet. Thus we get a 

 difference in elevation of 460 feet or a slope per mile of 61 feer 

 toward the west. In a similar way we. may find a slope, between 

 Lyons Falls and a point east of Fowlersville, of 67 feet per mile 

 westward. 



In the vicinity of Woodhull lake, at the western edge of the Old 

 Forge sheet, the Precambric elevation is 2000 feet while at Port 

 Leyden, 17 miles westward, it is 900 feet. The difference in alti- 

 tude is 1 100 feet which means a westward slope of nearly 65 feet 

 per mile. 



These comparisons clearly demonstrate that the Precambric sur- 

 face now slopes both southward and w^estward, but that the west- 

 ward slope is much steeper. The writer has compared Precambric 

 altitudes at many points over the Port Leyden, Remsen, Wilmurt 

 and Little Falfs quadrangles. The conclusion reached is that the 

 exposed Precambric surface along the southwestern Adirondacks 

 slopes both westward and southward ; that the slope toward the west 

 is steeper (being from 60 to ioq feet) than the slope toward the 

 south (being from 11 to 50 feet) ; and that the general southwest- 

 ward slope is greater in the Little Falls than in the Port Leyden 

 region. 



Slope of the Precambric surface w^here Paleozoics now cover 



Having acquired some idea regarding the slope of the exposed 

 Precambric surface it will now be of interest to determine the slope 

 of the Precambric surface where Paleozoics now cover. This may 

 be done by comparing altitudes of the Precambric within the Port 

 Leyden quadrangle with the Precambric altitudes as found in cer- 

 tain deep wells to the south, southwest and west. 



In the Campbell well 3 miles west of Utica, according to Prosser,^ 

 the Precambric was struck at 1500 feet below sea level, while at 



' Geol. Soc. Am. Bui. 1893. 4:101. 



