GEOLOGY OF THE REMSEN QUADRANGLE 7 



even until the whole region was under water. During the subsid- 

 dence, deposition of Paleozoic sediments went on, one layer above 

 another, the younger deposits overlapping each other and encroach- 

 ing upon the sinking land surface. Since the subsidence was not 

 entirely uniform on all sides certain local variations in deposition 

 occurred. 



The first of the deposits to form upon the sinking floor was the 

 Potsdam (Cambric) sandstone now found exposed nearly every- 

 where except along the southwest border. After this the sediments 

 changed in character and the limestones of the Beekmantown 

 (Lower Siluric) were laid down. Then followed the deposition 

 of the highly fossiliferous Trenton (Lower Siluric) limestones, 

 including the Lowville and the Black River limestones. The 

 fairly clear waters full of animal life then gave way to the muddy 

 waters of the Utica, when the Utica shales (Lower Siluric) were 

 deposited. At this time the Adirondack region was probably all 

 under water. Next came an uplift on the east and northeast where 

 deposition ceased. On the south and southwest, however, deposi- 

 tion continued and the successive formations of the Siluric and 

 Devonic above the Utica shale w^ere laid down. These Paleozoic 

 formations may now^ be seen as one passes from the Adirondacks 

 southward to the southern border of the State. 



The last period of igneous activity in the Adirondacks occurred 

 some time after the close of the Lower Siluric. This activity was 

 of minor extent and showed itself in the form of dikes. 



At some time after the deposition of the Utica shale the rocks, 

 especially along the southern border, were deformed chiefly by 

 faulting. A series of these faults extends across the Mohawk valley, 

 a small one being present within the limits of the Remsen quad- 

 rangle. The southern Adirondacks, including the Trenton Falls 

 district, have been subjected to erosion for a vast length of time, 

 certainly since the close of the Paleozoic and more than likely 

 since the Devonic. During this great lapse of time a large amount of 

 material has been removed. Doubtless the whole Remsen quad- 

 rangle was at one time covered by the Utica shales, which have 

 all been removed except along the western side. 



The superficial deposits, such as sands, gravels and clays, which 

 are so common over the Trenton Falls district were deposited 

 either directly or indirectly by the great ice sheet of the Glacial 

 age. From the geological standpoint this ice sheet was present 

 only quite recently and covered most of New York State. 



