BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 6, pp. 263-284 March 22, i895 



CRYSTALLINE LIMESTONES AND ASSOCIATED ROCKS OF 

 THE N0RTHWP:STERN ADIRONDACK REGION 



^ BY C. IT. SMYTH, JR. 



{Read before the Society December 28, 1894) 



CONTENTS 



Page 



Introduction 264 



Extent and character of the limestones 2(54 



Gneissic areas 266 



Igneous rocks 266 



Granite and diorite 266 



Gabbros 268 



First variety 268 



Area of occurrence 268 



jNIacroscopic characteristics 269 



Mineralogic composition and characteristics 269 



Effect of contact 270 



Relation of the gabbro to granite intrusions 270 



The gabbro as a basis of comparison 270 



Second variety of gabbro 271 



Area of occurrence 271 



Description of the rock 271 



Relations and origin 271 



Third variety of gabbro 27 1 



Chief characteristic 271 



Area of occurrence t 271 



Appearance in the field 272 



Characteristics of the feldspar 272 



Microscopic characteristics and mineralogic composition 27.") 



Chemical analyses 274 



Relation of gabbro to limestone 274 



Character of the transition 274 



Character of the contact 274 



Contact-metamorphism 277 



Endomorphic changes 277 



Exomorphic changes 278 



Metamorjihism of tiie limestones as a whole 281 



Relation of gjibbro to gneiss 282 



Diabase 283 



Summary 284 



XXXVII -Mui.i.. Opoi,. Hoc. Am.. Vol. r,. I8'.i4. . (263) 



