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NEW YORK STATE MUSEUM 



and the added thickness of the Black River was also insufficient 

 completely to fill theiu. In these instances it seems clear that the 

 slight elevations on which no deposit took place must have existed 

 as shoals, and that hence the water was very shallow, and the 

 shore line close at hand, as seems to have also been the case dur- 

 ing the Lowville. There are sections, as in the Moore quarry at 

 Pattersonville, measured by Prosser, in which the Black River 

 rests directly on the Beekmantown, though the Lowville occurs 

 thinly at its proper horizon, no great distance away, and such a 

 section is demonstrative of uneven surface. On the other hand, 

 the writer's work in the Little Falls region has shown that the 

 Black River there has a very patchy distribution, and that about 

 Middleville it is definitely absent, though the Lowville occurs 

 there in considerable strength, and this is thought to point to an 

 unconformity between the Black River and Trenton, the Black 

 River being absent because of uplift and wear, after its deposi- 

 tion and before the beginning of the Trenton. Not unlikely the 

 strong unconformity at Canajoharie is in part due to wear of this 

 date, and not all to be ascribed to the period of Postbeekman- 

 town erosion. This uplift seems to have been localized here at 

 the southeast, since only there is the Black River found to be 

 lacking. In the Mohawk region then, the shore line was close 

 at hand and was irregular, though not so much so as at the com- 

 mencement of the Lowville, and the one formation followed the 

 other with no sign of a break, the two deposits combined nearly, 

 but not quite, filling up the depressions ; thence ensued an uplift 

 about Little Falls, which brought about removal of the Black 

 River through wear and caused the Trenton there to rest on the 

 Lowville. 



With the oncoming of Black River time, rapid subsidence seems 

 to have been initiated on the east side of the region, the Chazy 

 basin becoming again submerged ; and the deposits thus laid down 

 must have encroached as widely into the heart of the Adirondacks 

 as the previous Chazy deposits had done. On the west side of 

 the region also the formation is everywhere present, and thicker 

 than on the south, so that the Black River sea was continuous 

 around the region, and must have widely submerged it. There 

 must have remained unsubmerged, however, an island of con- 



