380 NEW YORK STATE MUSEUM 



muds of the passage beds and Utica advanced on the region from 

 the east, and Trenton conditions persisted longer westward. In 

 other words, that, while the upper Trenton was accumulating in 

 comparatively clear waters, in the Trenton falls region, incur- 

 sions of mud were producing the lithologic combination of the 

 passage beds about Middleville and eastward, while yet farther 

 east shales were being laid down. This is by no means a new 

 suggestion, though the stratigraphic evidence for it has not been 

 so marshaled hitherto. Even if it be granted, it does not fully 

 explain the sudden increase in thickness at Trenton falls, when 

 compared with the much more trivial variations which character- 

 ize the whole length of the Kohawk valley below Canajoharie. 



Concerning the formation along the west side of the Adiron- 

 dacks, our knowledge is very fragmentary. As has been stated, 

 the heavy drift cover on this side of the region is an effective bar 

 to satisfactory areal work. Well to the north, about Watertown, 

 conditions are much better, and the Trenton is magnificently 

 shown. Emmons's descriptions show that it has the same litho- 

 logic characters here as at Trenton falls and elsewhere, consisting 

 partly of dark, fine grained, and partly of gray, crystalline lime- 

 stone, the former often intea^leaved with shales; also that often 

 the summit is graj^ and masmve, as at Treniton falls, which is 

 not the case in the Mohawk and Champlain valleys. He states 

 the thickness at Watertown to be about 300 feet, which, judging 

 from his estimates of thickness of the rocks in other parts of the 

 second district, is likelj' to be an underestimate.^ 



Quite fortunately the gas wells drilled within the past 20 years 

 to the west and southwest of the region help to bridge the gap 

 in the sections and furnish important data in regard to the thick- 

 ness of the formiation. The wells at Pulaski and Sandy Creek in 

 Oswego county, which are 55 miles northwest of Trenton falls, 

 and respectively 25 and 32 miles to the west of south of Water- 

 town, have been described, and the sections interpreted by Pro- 

 fessor Orton.2 As is often the case, it is difficult to determine 

 precise formation boundaries from the records, owing to a variety 

 of causes. At Sandy Creek the thickness of the Trenton is uncer- 

 tain but seem,s surelv as much as 600 feet. At Pulaski the wells 



^G€ol. N. T. 2d Dist. p.387-S8. 



^N. Y. State Mus. Bui. 30, p.434r48. 



