QUARRY MATERIALS OF NEW YORK 55 



the most widespread and the thickest of the calcareous sediments. 

 Among the individual members are included the Lowville, Black 

 River and Trenton beds in the order of sequence. In the lower 

 section they are heavily bedded and quite pure, but become shaly 

 toward the top. They have importance for building stone, cement 

 and lime manufacture. They are often highly fossiliferous. They 

 occur in the Champlain valley, but are more prominent on the 

 Vermont side than on the New York shores. Continuous with 

 the Vermont area, a belt extends across Washington county into 

 Warren and Saratoga counties. Another large belt begins in the 

 Mohawk valley near Little Falls and extends northwesterly with 

 increasing width to the St Lawrence river, overlapping onto the 

 Adirondack crystalline rocks. The upper limestone beds of the 

 Trenton pass gradually into shales, indicating an influx of mud. 

 This condition lasted through the Cincinnatian period when the 

 Utica, Frankfort and Pulaski shales of central New York were 

 laid down. In the Hudson valley and eastward there was a marked 

 preponderance of shales over limestones in the sedimentation 

 throughout the whole Lower Siluric period ; the great mass of shales 

 which has come to be known as the Hudson River formation began 

 to be deposited in fact as early as Cambric time. 



At the close of the Lower Siluric period, the Taconic disturbance 

 interrupted sedimentation in the area along the Hudson river and 

 upraised that section into dry land. The agencies of compression 

 and metamorphism which were forceful enough to produce a highly 

 folded and more or less metamorphosed condition in the shales, 

 limestones and sandstones of the east did not extend their effects 

 very far to the west. The Adirondack and Mohawk valley forma- 

 tions were not changed noticeably or disturbed from their normal 

 position, though possibly there was some faulting which initiated 

 the great meridional breaks along the eastern and southern Adiron- 

 dacks. In the Highlands regions the effects may have been much 

 more pronounced, as indicated by the intrusion of the great boss of 

 the Cortland rocks. Other deep-seated invasions may be repre- 

 sented by the serpentine masses of Staten Island and Rye and by 

 the Harrison diorite, though these are possibly of earlier date. 



The Ontario or Upper Siluric period was continuous with the 

 Lower Siluric as regards sedimentation in the interior of the State, 

 though on the borders of the Taconic land surface the two series 

 of formations are separated by a strong erosional unconformity. 

 The Upper Siluric was a time of shallow water accumulations. 

 In the basal members, as represented by the Oswego and Medina 



