GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 6l 



group lying between Chain lakes and Long lake. Adjoining quad- 

 rangles show the common occurrence of similar altitudes. It would 

 seem, therefore, that, if at all recognizable, remnants of the old 

 peneplain surface now lie somewhere betw^een 3000 and 3500 feet, 

 altitudes higher than this representing what were the more promin- 

 ent monadnocks. The concordance of altitudes is not very satis- 

 factory, and so it must be admitted that the proof is by no means 

 conclusive. At any rate, it is quite certain that the principal valleys 

 and depressions of the quadrangle have been carved out of v/hat 

 was an upraised and at least crudely developed Cretaceous peneplain. 



OUTLINE OF GEOLOGIC HISTORY 

 Those interested in the natural history of the Adirondack region, 

 but not familiar with geologic lore, might do well first to consult 

 the writer's New York State Museum Bulletin 168 entitled " The 

 Geological History of New York State." This work has been 

 prepared primarily for laymen. The only treatise on Adirondack 

 geology in general is Cushing's excellent Museum Bulletin 95.^ In 

 the very brief summary immediately following, the attempt is to 

 present only the most salient events now known to be recorded 

 w^ithin the Blue Mountain quadrangle with some reference to the 

 relation of these events to the geologic history of the Adirondacks 

 in general. 



Precambrian History 

 The oldest known geologic records in the Blue Mountain quad- 

 rangle are contained in the rocks of the Grenville series which, 

 in the light of present knowledge, are to be grouped with the oldest 

 known rocks of the earth's crust. Since these rocks are distinctly 

 stratified, very thick (many thousands of feet), and of w^ide areal 

 extent not only throughout the Adirondacks but also in eastern 

 Canada, we may be sure that the earliest known condition of the 

 area of the quadrangle w^as the presence of a sea in which the 

 Grenville strata w^ere being deposited layer upon layer. As yet 

 nothing is known either regarding the floor of this very ancient sea 

 or of the land masses from which the sediments were derived. Dur- 

 ing part of Grenville time the sea water was very clear as shown 

 by the comparative purity of the great masses of limestone. That 

 the Grenville ocean persisted for some millions of years is proved 



1 Since the above was written the author has prepared a small treatise for 

 laymen entitled " The Adirondack Mountains." This contains an account of 

 the geography and geology of the region in simple language. It is now being 

 published by the New York State Museum. 



