GEOLOGY OF THE VICINITY OP LITTLE FALLS 11 



seems to have been thickest on the northeast, though the dis- 

 crepancy is not so marked as in the case of the Potsdam and 

 Beekmantown formations. 



Following the deposition of the Utica formation, came a move- 

 ment of disturbance and uplift of the region on the northeast and 

 east. This apparently raised the present Champlain .valley and 

 northern Adirondack region above sea level, while the southern 

 portion was not affected and remained submerged, so that the 

 deposit of sediment continued on the south, though interrupted 

 on the north. The successive Upper Silurian and Devonian rocks 

 are now found outcropping in regular order as one goes south 

 from the map limits, presenting their beveled edges to daylight. 

 They all extended farther north originally. It would seem very 

 probable, nay almost certain, that the higher Silurian rocks were 

 deposited over the map limits and have since been removed by 

 erosion. Quite possibly the Devonian also, in Avhole or in part, 

 was so deposited. 



There is a certain amount of evidence going to indicate that, 

 during the late Silurian and early Devonian, the northern region 

 became depressed again for a time and . received deposit on its 

 somewhat worn surface. But such deposit has been since wholly 

 removed by erosion so far as northern New York is concerned, 

 leaving us in entire ignorance as to its thickness, character and 

 extent. Had these deposits been thick and of wide extent, how- 

 ever, we might reasonably hope to find remnants of them today, 

 here and there. There is no evidence whatever that smj rocks 

 of later age than the Devonian have ever been dej)osited in, or 

 about the Adirondack region, the recent Champlain clays and 

 sands being of course excepted, and the evidence for the deposit 

 of any of the Devonian is of the scantiest sort. 



Probably coincident with the Taconic disturbance at the close 

 of the Lower Silurian, occurred the last manifestation of igneous 

 activity in the Adirondack region. This was mainly confined to 

 the near vicinity of Lake Champlain, at least so far as the New 

 Tork side is concerned. The igneous rocks of this date are now 

 found in dikes, and occasional somewhat larger intrusive masses. 



