GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE II 



classed with the oldest known formation in the crust of the earth. 

 They are very largely, at least, stratified rocks, the original sedi- 

 ments such as limestones, sandstones and shales having been 

 thoroughly metamorphosed into crystalline limestones, quartzites, 

 and various schists and gneisses. Since the foliation and stratifica- 

 tion planes are always coincident, it seems quite certain that the 

 Grenville strata have never been subjected to very severe lateral 

 compression, at least not sufficiently great ever to have obliterated 

 the bedding surfaces. x\s judged by the character, great thickness 

 and areal extent not only throughout the Adirondack region but 

 also through much of eastern Canada, we may safely conclude that 

 the Grenville beds were deposited under marine waters much as 

 were the sediments of later geologic periods. Concerning the 

 character and location of the lands from which the sediments were 

 derived and the sea floor upon which they were deposited, we are 

 at present ignorant. It is certain that the Grenville rocks are many 

 milHons of years old. 



Areal distribution. Approximately 26 square miles of Grenville 

 rocks are separately represented on the accompanying geologic map 

 of the Blue Mountain quadrangle. There must also be added some 

 10 or 12 square miles more represented in the mixed gneiss areas 

 and also inclusions mapped and unmapped in the igneous rocks. 

 Thus about one-sixth of the area of the quadrangle is occupied by 

 Grenville strata. On the Newcomb sheet the writer has seen large 

 areas of Grenville; Gushing has mapped considerable areas on the 

 Long Lake sheet ; and the writer has seen many Grenville outcrops 

 on the Tupper Lake sheet along the road from Long Lake to Long 

 Lake West. Our knowledge is therefore sufficient to make it 

 positive that the Grenville is prominently represented in the midst 

 of the Adirondack region. Accordingly, certain older views 

 implying very slight development of the Grenville there must be 

 abandoned. 



Within the quadrangle no attempt has been made to map the 

 different facies of the Grenville separately because the heavy drift 

 accumulations and consequent scarcity of exposures in certain por- 

 tions of the Grenville valleys render any satisfactory areal sub- 

 divisions impossible. To a very considerable extent the crystalline 

 limestone with its closely associated hornblende and pyroxene 

 gneisses might be separately mapped, but it has seemed best to 

 allow the known extent of the limestone areas to be brought out 

 by indicating the actually observed outcrops of that rock upon the 

 geologic map. 



