BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 27, PP. 685-718, PLS. 25-30 DECEMBER 11, 1916 



TEIASSIC KOCKS OP ALASKA 1 



BY GEORGE C. MARTIN 



(Presented in abstract before the Society December 30, 1915) 



CONTENTS 



Page 



Introduction 686 



Description of the Triassic rocks of Alaska 687 



Occurrence and general character 687 



Character of the pre-Triassic basement 688 



In general 688 



Permian ( ? ) strata 6S9 



Pre-Triassic (?) slates of undetermined age 689 



Early Triassic ( ?) volcanic rocks 6S9 



Middle Triassic rocks 690 



Upper Triassic rocks 690 



Chitina Valley (Wrangell Mountains) 690 



Nutzotin Mountains and Alaska Range 696 



Cook Inlet and southwestern Alaska 697 



Southeastern Alaska 700 



Yukon River 701 



Northeastern Alaska (Firth and Canning valleys) 702 



Northwestern Alaska 703 



General character and correlation 704 



Middle Triassic 704 



Upper Triassic 706 



General distribution 706 



Dawsonites zone 706 



Zone of Halobia cf. mpcrba. 707 



Coral-reef horizon 709 



Chert horizon , 710 



Zone of Pseudomonotis subcircularis 710 



Geologic history of Alaska in Triassic time 717 



1 Published by permission of the Director of the U. S. Ecological Survey. 

 European stratigraphic terms of lower than system rank are used in this paper for 

 the purpose of indicating- probable or possible correlations and without any intention of 

 incorporating them into the American nomenclature. 



Manuscript received by the Secretary of the Geological Society May 15, 1016. 



(685) 



