120 NEW YORK STATE MUSEUM 



The West Point quadrangle lies between these two representative 

 areas, and if there is a definite determinable geologic succession, it 

 would seem to be worth while to attempt a correlation of the prin- 

 cipal members and match the major historical steps. In spite of the 

 greater distance, such an attempt looks more promising for the 

 Adirondacks than for the New Jersey area, chiefly because the suc- 

 cession of events has been more definitely determined there by long- 

 continued work and perhaps the steps are more cleai"ly indicated. 



Comparison with the Adirondacks. In the southern Adirondacks, 

 the essential items, following the later work of Kemp " and Ailing ^ 

 may be listed briefly as follows : 



a The oldest member ^ — the Grenville 



Tliis is made up of completely metamorphosed formational 

 remnants of very complex original character, including limestones, 

 shales and sandstones, with a complicated subsequent metamorphic 

 and injection history. 



Such a series is also represented in the West Point area, not on a 

 \ery large scale, but with all the variety and complication usually 

 assigned to the Grenville of other regions. It is here also, as in the 

 Adirondacks, the most ancient member of the whole series and has 

 had in general the kind of a history formulated for this formation by 

 the Adirondack geologists. On the basis of essential identity of 

 character, and relation to other members, the term Grenville has been 

 used with the same meaning in this area. There appears to be no 

 good ground for doubt about this correlation. 



b The oldest intrusives — Laurentian 



These are said to include meta-gabbro and granitic intrusions and 

 injections which, together with the Grenville, are involved in and 

 modified by all the other members. 



This division is not so clear in the West Point quadrangle as it 

 appears to be in the Adirondacks. But there are occurrences of 

 similar habit in the area always appearing as injections of the Gren- 

 >ille or as gneissic products that appear to be older than the more 

 definite simple granite units that make up the major part of the 

 area. Some of these developments are moderately basic, giving 

 a dioritic facies in many places. This is the Pochuck gneiss, in part, 

 of the New Jersey geologists and the type seems to be very much 

 better represented farther west than in the West Point Quadrangle. 



^Kemp, J. F. Geology of the Mount Marcy Quadrangle. N. Y. Slat( 

 Mus. Bnl. (in press"). 



^Allinn-, H. L. Some Problems of the Adirondack Precambrian. Am. 

 Jour. Sci. 48:47-68 (1919) 



