138 I. C. RUSSELl 1 RFAI I GEOLOGY OF ALASKA. 



Dawson's report on an exploration in the Yukon district contains a 



description of tin untry traversed by me from the mouth of Felly river 



to Juneau, as already Btated. Dawson reports an absence of glacial records 

 along the Yukon I Telly) below the mouth of Big Salmon river, ami their 

 presence higher up in the Bame drainage system. 



McConnell's observations on the glaciation of this region have already 

 been referred to. His conclusions were that there are no records of glacia- 

 tion along the Porcupine or along the Yukon below the neighborhood of 

 the month of Big Salmon river, but above that locality there are abundant 

 records of a northward (lowing ice sheet, as had been determined by Dawson. 



The conclusions of Dawson and McConnell agree iu all essential partic- 

 ulars, and demonstrate that there is a great area to the north of the northern 

 limit of the Cordilleran glacier, as named by Dawson, which was not occupied 

 by iee (luring the Pleistocene. 



My own conclusions accord with those just referred to. The central and 

 northern parts of Alaska, like a large portion of the North West Territory, 

 \\a- not. in my opinion, occupied by ice in recent geological times. 



PERSONAL OBSERVATIONS. 



Unalaska. — While at Iliuliuk I examined the neighboring region, and 

 looked especially for evidences of former glaciation. In this search I was 

 unsuccessful. I found neither glaciated surfaces, perched bowlders, moraines, 

 bowlder clays, nor any of the well-known records of ice action. The rugged 

 topography of Unalaska and neighboring islands is sufficient to show that 

 l his portion of the Aleutian chain has not been abraded by a great ice sheet. 



In .-ailing along the shores of Unalaska and neighboring islands one sees 

 round-bottomed valleys opening to the sea. These valleys have the charac- 

 teristic cross-profile of glaciated troughs. On some of the higher peaks 

 there are cirques similar in every way to those so common about summits 

 that have been centres of ice accumulation. I examined one of these cirques 

 on the north side of Mount Wood.' some four miles south of Iliuliuk, and 

 at a heighl of about 2,000 feet, but found no evidence of excavation by 

 glacial ice. The cirque was partially filled with BUOW at the time, and this 

 may have concealed Btriated lock surfaces and moraines visible later in the 

 • ason. 



The presence of glaciers on the side of Moun I Makooshin (Makushin), the 

 highest peak on the island, reported by T. A. Blake,1 together with the 

 indication of former local ice 3treams furnished by the 1 -shaped cafions and 

 the cirques just mentioned, suggest that local glaciers of large Bize, but of 

 the Alpine type, radiated from Unalaska during the glacial epoch. 



ttnld Mt. Peak ' on 1 urvey Chart of Captain's Bay, 1876. 



ipon the Geology of Alaska; In Ex. Doc. No 177, 40th Congrest I esaion, Hoi 



; tatlVl -, V. -, pp, ;| 1 



