120 NEW YORK STATE MUSEUM 



the Tribes Hill which certainly differ from bed 6 at the top of 

 the formation in the section in the village just given. As the 

 Lowville and other Black River limestones are thicker in the 

 quarry at the depot than in the village section it is thought 

 likely that, in part, the westward dip may signify descent of the 

 beds into an original synclinal basin in which the Tribes Hill 

 formation retained beds that were eroded in nearby areas. 



Western sections 



It was our intention to study the section at Sprakers about mid- 

 way of the valley, where the Preoambric is brought up on the west 

 side of the fault, and the full thickness of the " Calciferous " is 

 shown. We were, however, unable to do so and hence can not 

 state whether the contact between the Little Falls dolomite and 

 Tribes Hill limestone is here exposed or not. However, consider- 

 ing that wherever observed the formations maintain unconform- 

 able relations to each other there seems no reason to doubt that 

 similar conditions will be found to obtain also at Sprakers. Prosser 

 has given two carefully measured sections at this point, one of the 

 cliff at the West Shore Railroad cut, the other along Flat creek. 1 

 The Potsdam is absent, having disappeared through overlap. The 

 first section shows a thickness of 490 feet, the lower 385 feet of 

 which belong apparently to the Little Falls, the upper 40 feet be- 

 long certainly to the Tribes Hill, while between the two is an in- 

 terval of 65 feet with infrequent exposures which in all probability 

 belongs mostly or entirely with the Tribes Hill. The summit of the 

 formation is not reached. Prosser reports Cryptozoon about 200 

 feet above the base in the Little Falls, and the Tribes Hill fauna 

 in the upper 40 feet of the section. The Flat creek section, capped 

 by Mohawkian limestone, shows 190 feet of rock, the upper 95 feet 

 of which Prosser assigns to the Tribes Hill (fucoidal beds) and 

 the lower portion to the Little Falls. Except for lack of knowl- 

 edge in regard to evidence of unconformity between the two forma- 

 tions and the precise horizon of the break, the section is perfectly 

 clear. 



Section at Little Falls 



The best section at Little Falls is that along the creek to the 

 northwest of the town, where the upper beds and all the contracts 



*N. Y. State Geol. 15th An. Rep't, p. 641-43. 



