44 RECONNAISSANCE IN NORTHERN ALASKA IN 1901. 



eroded the rocks and brought down deposits of gravel and drift, as shown in PI, 

 VI. B. Such deposits, however, rarely attain a thickness of more than Km feet. 



The John River system, just described, is believed to be a fair type of the other 

 adjacent drainage systems of the mountains, such as Hokotena River or Wild Creek 

 and North Fork, which trend parallel to it and also How south into the Kovukuk. 



KOYUKUK PROVINCE. 

 GENERAL FEATURES. 



This province, extending from the southern base of the mountains 120 miles 

 southwestward to the limit of the map at the sixty-sixth parallel, lies mainly in the 

 northwestern part of the large basin of the Koyukuk, which forms the northwestern 

 part of the Yukon Basin. It consists mainly of a rolling or hilly country of known 

 and supposed Mesozoic rocks, whose hills rise to elevations of from 1,000 to 3,000 

 feet, while the main valley floors lie at approximately 600 feet. 



The general accordance in height of the hills and ridges of this province at two 

 different levels strongly suggests that the present topography has been carved from two 



--_^_ ~^~^-^-^-. ENDICOTT PLATEAU S50O* 





\ / \ / ^v YUKON? PLATEAU 3000* 



S 





KOYukuk Plateau 

 1200' 



SEA LEVEL | 



Fig. 2. — Diagrammatic profile showing relations of Endicott, Yukon, and Koyukuk plateaus. 



former plateau features (see fig. 2). Though, for need of further investigation, this 

 question can not be discussed in detail in this place, it may be noted that of these two 

 features the lower level, at about 1,200 feet, is relatively distinct and well marked, 

 and represents the general elevation of the land mass over the larger part of this 

 portion of the Koyukuk Basin, as may be seen on the map (PI. II). For it the name 

 Koyukuk Plateau is suggested. 



The higher level, which also suggests a former plateau now dissected and largely 

 removed by erosion, lies at about 3,000 feet, but it is indefinite. Its best expression 

 occurs along the base of the mountains, where portions of nearly flat-topped ridges, 

 rising gently northward, soon merge into the foothills of the mountains, while to the 

 south they become lost in irregular ridges and hills, descending to the lower or 

 Koyukuk Plateau. This higher level, where formerly observed, at an elevation of 

 from 2,500 to 3,000 feet, to the east, on Chandlar and upper Koyukuk rivers, 

 near the sixty-seventh parallel, was supposed to represent the Yukon Plateau,'' but 



a For a more complete description of the Koyukuk Basin the reader is referred to Preliminary report on a reconnais- 

 sance along the Chandlar and Koyukuk riyers, Alaska, in 1899: Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2, 1900, 

 p. 467, See, also, Recent work of the United States Geological Survey: Bull. Am. Geog. Soc, vol. 34, No. 1, Feh., 1902. 



bSchrader, F. C, Preliminary report on a reconnaissance along the Chandlar and Koyukuk rivers, Alaska, in 1899: 

 Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2, 1900, p. 99. 



