THE CANTWELL FORMATION: A CONTINENTAL 



DEPOSIT OF TERTIARY AGE IN THE 



ALASKA RANGE^ 



JOSEPH E. POGUE 



United States Geological Survey, Washington, D.C. 



Introductory statement. — 'The Cantwell formation comprises a 

 series of conglomerates and finer clastic sediments of important 

 though restricted development within the Alaska Range. These 

 rocks form a belt from 3 to 23 miles in width, which has its begin- 

 ning near the northeast base of Mount McKinley and extends 

 thence eastward for at least 100 miles to Cathedral Mountain at 

 the head of Susitna River. Its members attain their most typical 

 and maximum expression adjacent to . the Nenana Valley, inter- 

 mediate between those two points. 



Historical. — -In 1898, during a hasty exploratory trip into the 

 Alaska Range, Elridge noted a "series of conglomerates and 

 coarse sandstones" on the Nenana (then called Cantwell) River, 

 between two tributaries later designated as Jack River and Yanert 

 Fork, and referred briefly to this group of rocks as the Cantwell 

 Conglomerate.^ Brooks and Prindle in 1902, on a geological 

 reconnaissance of the Mount McKinley region, came across similar 

 rocks at the foot of Muldrow Glacier^ near Mount McKinley, 

 and following along their northern border traced their extension 

 eastward into the Yanert Fork basin, mapping the area as the 



" Published with the permission of the Director of the United States Geological 

 Survey. The field work upon which this paper is based was done by F. H. Moffit 

 and the writer, and the latter is indebted to Mr. Moffit for helpful suggestions in its 

 preparation. 



2 George H. Elridge, "A Reconnaissance in the Sushitna Basin and Adjacent 

 Territory, Alaska, in 1898"; United Stales Geol. Survey Twentieth Ann. Rept. (1898- 

 99), Pt. 7, p. 16; also map 3. 



3 They also found a small area 75 miles southwest of that point near Mount 

 Russell of the Alaska Range. 



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