This Section consists of island-arc volcaniclastic assemblages associated with other Cenozoic rocks. Portions are underlain by Wrangellia terrane. Since much of the area consists of steep rocky slopes, ice fields, and glaciers, soils are infrequent and generally thin and stony. Principal soils include Lithic Cryorthents, Typic Cryorthents, Pergelic Cryochrepts, and Pergelic Cryumbrepts. Potential Natural Vegetation.
Most areas are barren of vegetation.
Where vegetation occurs, alpine tundra communities of prostrate shrubs, forbs, grasses, and lichens predominate. Trumpeter swans nest in the river valleys, as do widgeons, lesser scaups, and greater scaups. Some of the best habitat for Dall sheep in Alaska occurs in this Section. Gray wolves are also abundant. Grayling occur in clear-water streams.