Kirk — Paleozoic Glaciation in Alaska. oil 



Art. XIX. — Paleozoic Glaciation in Southeastern Alaska ; 

 by Edwin Kirk.* 



Evidence of glaciation in the Paleozoic is of interest 

 even though the discovery of tillites has become the com- 

 monplace of geologic field work. During the past field 

 season a tillite of Silurian age was found in southeastern 

 Alaska. This is particularly interesting as being the 

 first record of Silurian glaciation. Fairly conclusive 

 evidence of Permian glaciation was also secured. There 

 is some reason to believe that glacial deposits occur in 

 the Devonian of the region as well. 



Cairnes in 1914 described a conglomerate of "Permo- 

 Carbonif erous ? ' ' age which he found on the Alaska side of 

 the international boundary just north of 65° north latitude. 

 He considered the conglomerate as possibly of glacial 

 origin. The conglomerate has a thickness of 700 to 800 

 feet and his description leaves little doubt but that it is a 

 true tillite. One of his arguments against the probable 

 glacial origin of the beds is that no other deposits of like 

 character are known in Alaska. This objection has been 

 met by the discovery of conglomerates in southeastern 

 Alaska that apparently hold the same stratigraphic posi- 

 tion and have most of the characteristic features of till- 

 ites. The conglomerate described by Cairnes has been 

 accepted by Coleman as a tillite without question. Apart 

 from this discovery of Cairnes no other paleozoic glacial 

 deposits have been reported from Alaska. 



The Silurian conglomerates which have proved to be of 

 glacial origin were first noted by the Wrights 1 in their 

 bulletin on the Ketchikan and Wrangell mining districts, 

 Alaska. They were given an estimated thickness of 

 1200 feet and were placed within and at the base of the 

 Lower Devonian. No special description of the con- 

 glomerates was given by the Wrights and no suggestion 

 of possible glacial origin was made. These conglom- 

 erates are a conspicuous feature of the area on the west 

 coast of Prince of Wales Island bordering on Davidson 

 Inlet and Sea Otter Sound. The con.o-lomerates are 

 found scattered over an area of some 200 or 300 square 



* Published by permission of the Director of the U. S. Geological Survey. 

 1 Wright, F. E. and C. W., IT. S. Geol. Survey, Bull. 347, 1908. 



