lOO NEW YORK STATE MUSEUM 



these igneous injections are therefore younger than the gneiss and 

 are very large and abundant in certain cases. The granite of Storm 

 King, Crows Nest and Breakneck ridge belongs to this type. 



Following the sedimentary cycle represented by the above series, 

 and perhaps others not now preserved, the region was folded into 

 a mountain range, the series was extensively metamorphosed and 

 passed through a long period of erosion during which it was again 

 reduced to sea level position and began to accumulate a new series 

 of sediments. 



The lowest beds occurring upon this foundation are sandstones, 

 now changed into quartzite. In places they are conglomeritic, and 

 may now be seen projecting into the valleys along the Highland 

 border. This formation is of Cambric age, and is from 200 to 600 

 feet thick in favored places. It forms an almost continuous belt 

 along the north side of the Highlands except where cut out by 

 faulting, and extends with similar breaks beneath the later sedi- 

 ments northward. This quartzite is known as the " Poughquag." 



Upon the quartzite of this series there w^as developed a succes- 

 sion of limestone beds at least 900 to 1000 feet in thickness. This 

 formation is known as the " Wappinger " and includes some beds 

 that are of Cambric but for the most part of Ordovicic age. 



The final member of this series is a shale and shaly sandstone 

 in places changed to slate. It is quite variable in actual character 

 and has a great thickness, never yet successfully estimated, but 

 probably several thousand feet. This is the so called '' Hudson 

 River slate " series. In this region they are of Ordovicic age. 



This is the succession w^hich the proposed Hudson river lines 

 has to penetrate in a pressure tunnel. Later Siluric and Devonic 

 strata lie in the immediate vicinity of this alternative line, but add 

 no complication to the problem as it now stands. Therefore no 

 other formations need be considered except the glacial drift. This 

 covers almost every rock surface and is deeply accumulated in 

 some places, notably in the narrow gorges and valleys, obscuring 

 the finer original topographic lines. 



A summary of the history of the formations chiefly involved in 

 this problem with a suggestion of later erosion activities may be 

 tabulated as follows: 



Cenozoic 



Glaciation 



Reelevation 



Erosion (interrupted) 



Elevation (rejuvenation) 



