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NEW YORK STATE MUSEUM 



faults at a few points on this line, as in the south end of the 

 Gross quarry, and in the ridge of Oriskany west of the Gross 

 residence, by which the apparent thickness of the Becraft and 

 Oriskany beds is somewhat increased, but the order of super- 

 position of the formations is undisturbed. 



On the line of section 4, however, taken a few hundred feet 

 north of the avenue, the conditions are quite different. The 

 sequence of the formations is normal up to the Becraft lime- 

 stone of Gross quarry, and then a prominent thrust plane cuts 

 off the Becraft, and above the plane is found the Manlius lime- 

 stone. Above the Manlius and to the westward the formations 

 are repeated in normal order; Manlius, Coeymans, New Scot- 

 land, Becraft, to the western slope of the hill, which at the 

 line of this section is cut into the almost vertical Port Ewen 

 beds. 



Several hundred feet farther north the same conditions are 

 found along the line of section 5, plate 5, which passes through 

 the White lime quarry, W- W on map, plate 2. 



The White lime quarry overthrust fault, which is indicated on 

 map, plate 2, by the heavy black line marked 1-1-1-1, has been 

 traced by us northward from Gross quarry to where it passes 

 just east of Terry triangulation station, and throughout this 

 distance its position and horizon were found to be remarkably 

 constant. It follows very closely the western edge of the east- 

 ernmost Becraft limestone vein, and its location is usually in- 

 dicated by a more or less prominent escarpment on the over 

 thrust side or by a gully of erosion in the somewhat crushed 

 Port Ewen beds below the thrust plane. 



At the middle of the Gross quarry, about 200 feet 

 north of Delaware avenue, the Becraft limestone strikes n. 70 i 

 dips 20° n. w., and has above it at the edge of the quarry 

 face a few feet of lower Port Ewen beds, which are continued 

 along the southerly slope of the hill to a point back of the 

 Gross residence. At the north end of the quarry the Becraft 

 strikes n. 65° e., dips 20° n. w., and its upper portion, the 

 thin blue layers, are cut off by the thrust, above which 

 the Manlius limestone appears with strike n. 80° e., dip 5° n. 

 These Manlius beds just above the thrust plane are the thinh 

 bedded, dark blue gray layers containing Spirifer vanux- 



