512 Kirk — Paleozoic Glaciation 



in 



miles in this immediate region, and further study would 

 no doubt considerably extend the range to the south, east, 

 and north. The best exposures of the Silurian glacial 

 beds seen were on Heceta Island, although good outcrops 

 are to be found on the south shore of Kosciusko Island, 

 about 15 miles to the north. Apparently the same beds 

 occur along El Capitan passage betwen Kosciusko and 

 Prince of Wales islands. At the north end of Kuiu 

 Island, some 125 miles to the north, a bowlder bed holds 

 the same stratigraphic position and, I believe, represents 

 the same glacial deposit. Kosciusko and Heceta islands, 

 where the best Silurian glacial deposits are to be found, 

 lie between 55° and 60° north latitude, and 133° and 134° 

 west longitude. These islands are situated on the west 

 coast of Prince of Wales Island, toward the northern end. 

 Prince of Wales Island is the large island of the south- 

 eastern Alaska group, the southern point of which just 

 clears the Alaskan-Canadian boundary. Kuiu Island 

 lies to the north and slightly west of Prince of Wales 

 Island. 



The most favorable locality for an examination of the 

 conglomerate is in the large bay about midway on the 

 north shore of Heceta Island. The coast here is well pro- 

 tected from storms and there is a continuous, outcrop of 

 the limestone underlying the conglomerate, the conglom- 

 erate itself, and the overlying limestone. In places the 

 conglomerate is well broken down by weathering, making 

 the collection of pebbles and bowlders an easy matter. 

 As exposed, the beds outcrop along the shore between tide 

 levels and give an outcrop perhaps 2000 to 3000 feet in 

 length. The beds strike about N. 30° W. and have an 

 average dip of about 30° N.E. At the east end of Heceta 

 Island, on what is locally known as Blue Bluff, several 

 hundred feet of the conglomerate are exposed in an 

 abrupt face together with the basal portion of the over- 

 lying limestone. Both this exposure and that on the 

 south side of Kosciusko Island are difficult of access 

 except under exceptionally favorable weather conditions. 



The glacial conglomerate is underlain and overlain by 

 fossiliferous marine limestones. The succession of beds 

 is clearly shown and unmistakable. The same relations 

 can even more clearly be seen on the bold cliff at the east 

 end of Heceta Island as to the upper limit of the conglom- 

 erate. The relations of the conglomerate to the under- 



