32 



NEW YORK STATE MUSEUM 



to indicate a thickness of at least 200 feet. Northeastward from 

 Mayfield there is a thickness of 160 feet with neither top nor 

 bottom shown. Thus the thickness is practically the same as for 

 the region around Saratoga (if the Hoyt limestone be excluded). 



Among the many excellent outcrops in the region are the follow- 

 ing: northeastward from Mayfield; the vicinity of Cranberry 

 Creek; two miles north-northwest of Cranberry Creek; the 

 west side of Bunker hill; in Gifford valley; just southeast, 

 and two miles south-southeast, of Northville; two and one- 

 half miles north, and one and one-half miles southwest, of Batch- 

 ellerville ; at Northampton and one mile northward ; at Union Mills 

 and one mile south-southeastward ; three-fourths of a mile west, 

 and two and two and one-half miles east, of Broadalbin ; at several 

 points between Perth and West Galway; on the road east of West 

 Galway; and at many places within the dolomite areas around 

 Galway. 



An important feature of the dolomite formation is the existence 

 of a distinct erosion surface at its summit. Within the quad- 

 rangle, with one or two possible slight exceptions, the Tribes Hill 

 limestone is absent and the Black River-Trenton limestone (gener- 

 ally the Lowville) everywhere rests upon the eroded surface of the 

 dolomite. Near Rock City Falls (Saratoga sheet) such Ordovicic 

 (Black River) limestone clearly rests upon an eroded surface of 

 the dolomite. One and one-half miles southwest, and one mile 

 south, of Galway similar phenomena may be observed and, at the 

 first named place, a few pieces of the dolomite are included in 

 the overlying limestone. Along Kennyetto creek, two miles east 

 of Broadalbin, the Trenton-Lowville is practically in contact with 

 the dolomite and the very perceptible dip of both formations to the 

 west shows clearly that the Trenton-Lowville occupies a depression 

 in the surface of the dolomite. Three-fourths of a mile east of 

 Mayfield and also at Kegg's quarry (just east of Cranberry Creek) 

 the Lowville is practically in contact with the dolomite although at 

 the latter place a slight touch of the Tribes Hill limestone may be 

 present. 



TRIBES HILL LIMESTONE 



The Tribes Hill limestone as recently named by Ulrich and 

 Cushing 1 comprises essentially the " fucoidal beds " so long known 

 in the Mohawk valley and is to be correlated with the lower por- 

 tion of the Beekmantown of the Champlain valley. According to 



l N. Y. State Mus. Bui. 140, p. 99. 



