﻿Education Department Bulletin 



Published fortnightly by the University of the State of New York 



Entered as second-class matter June 24, 1908, at the Post Office, at Albany, N.Y., 

 under the act of July 16, 1894 



No. 485 



ALBANY, N. Y. 



December 15, 1910 



New York State Museum 



John M. Clarke, Director 

 Museum Bulletin 145 



GEOLOGY OF THE THOUSAND ISLANDS REGION 



ALEXANDRIA BAY, CAPE VINCENT, CLAYTON, GRIND- 

 STONE AND THERESA QUADRANGLES 



H. P. CUSHING, H. L. FAIRCHILD, R. RUEDEMANN AND 

 C. H. SMYTH JR 



PAGE 



Introduction 5 



Location and character 6 



Summary of geologic history 8 



Igneous intrusions 9 



Close _ of the long period of 



erosion 14 



Paleozoic sediments 14 



Subsequent history of the 



region 20 



The Pleistocene 23 



The rocks 24 



Precambric rocks 24 



Great Precambric erosion 53 



Paleozoic rocks 54 



Precambric surface under- 

 neath the Potsdam 54 



Potsdam sandstone 60 



Theresa and Tribes Hill forma- 

 tions 64 



Pamelia formation 68 



Mohawkian series 79 



Summary of Paleozoic oscilla- 

 tions of level 92 



Dip of the Paleozoic rocks 98 



Rock structures 99 



Foliation 99 



Joints 103 



Folds 108 



Faults 118 



Topography 121 



PAGE 



Paleozoic altitude and climate. . 122 



Amount of erosion 123 



Original drainage 124 



Tertiary uplift 125 



Tertiary drainage 125 



Plateaus, terraces, scarps 129 



Lakes 13 1 



Underground drainage 133 



Pleistocene geology 136 



History 136 



Physiography 141 



Glacial deposits . 150 



Glacio-aqueous deposits 156 



Glacial erosion. • • • ■ • 159 



Prewisconsin glaciation 1 64 



Economic geology 17 2 



Road metal, 173 



Granite quarries 174 



Sandstone quarries: . . • . 174 



Limestone quarries 175 



Petrography of some Precambric 



rocks 175 



Bleached granite 177 



Picton granite 181 



Alexandria syenite 182 



Granitized amphibolite and 

 amphibolitized granite 

 (soaked rocks) 184 



Index 180 



