386 Merrill — Metamorphic Strata of S. E. New York. 



Highlands and Garrisons. It has not yet been determined 

 whether they should be regarded as part of the system to which 

 the two lowest groups or members belong, nor have their rela- 

 tions been determined, with respect to the Manhattan Group 

 (hereafter defined). As before stated, no Ordovician or Cam- 

 brian Rocks have been found to rest upon them and hence 

 their pre-Cambrian age cannot, as yet, be predicated with cer- 

 tainty. 



The thickness of the pre-Cambrian rocks in the Hudson River 

 Valley may, therefore, be stated as between 2300 and 2800 

 feet. As to their age, it is difficult to predicate anything on 

 account of their isolated position. The " upper member," or 

 granulitic group may or may not be the equivalent of the 

 Huronian. There is nothing but its unconformable position 

 immediately below the Cambrian quartzite to suggest such 

 equivalence, and as it seems to be conformable to the " basal 

 member " that would have to be included in the same horizon. 



The magnetite beds of this region have been compared by 

 Dr. Britton to those of the Grenville series in Canada, and 

 they may be equivalent but until the Laurentian of Eastern 

 Canada has been studied and classified with the aid of modern 

 methods of research any attempt at correlation will be unsatis- 

 factory. 



The stratigraphy of the Highland region as displayed in the 

 section along the Hudson River is very simple. A small num- 

 ber of anticlinal ridges, 900 to 1700 feet in height, with a 

 northeasterly trend, are intersected by the Hudson River valley. 

 Along the lines of these the basal member of the Archaean is 

 exposed and resting on their flanks and in the synclinal troughs 

 the rocks of the Iron-bearing Group appear. 



The most northern axis is that of the Fishkill range which is 

 probably a continuation of the Wawayanda Mountain axis of 

 Northern New Jersey, along which line in Orange Co.'N. Y. 

 occur a number of isolated hills of gneissic rock known as 

 Sugar Loaf Mountain, Goose-Pond Mountain, Peddler Hill, 

 Rainer Hill, Mosquito Hill, Round Hill and. Woodcock Hill. 



Second is that of Storm King and Breakneck Mountains, 

 closely related orographically to the axis of Crow Nest Moun- 

 tain and Bull Hill or, as the latter is sometimes called, Mt. 

 Taurus. There is probably a fault line between these two axes 

 and nearly parallel to them, but the structural details have not 

 been accurately determined. A fourth axis is that which 

 crosses the Hudson at West Point. A group of axes crosses 

 the Hudson along the lines of Fort Hill, Sugar Loaf Moun- 

 tain, Anthony's Nose and Bear Hill and finally the anticlinal 

 of Manitou Mountain and the Dunderberg closes the succession. 

 These folds generally pitch steeply to the S.W. In this re- 



