The section lies in the hitherto unexplored part of northern Alaska. It extends from the 66th parallel north latitude roughly along the 152d meridian by way of the Koyukuk, John, Anaktoovuk, and Colville rivers, a distance of nearly 400 miles, to the Arctic coast*
Geographically the region traversed by the section comprises three distinct provinces, that of the Koyukuk or southern, the mountain or middle, and the Arctic slope or northern.
This province, extending from the 66th parallel more than 100 miles northeastward to the southern base of the mountains, lies mainly in the northwestern part of the large Koyukuk basin.† The province in general consists of a rolling country composed essentially of Mesozoic rocks whose low, rounded hills and ridges vary from 1,000 to 3,000 feet in elevation. It is supposed to represent the Koyukuk portion of the Yukon plateau, but which . . .