Denali-Yukon, Domain 9

The Denali-Yukon domain occupies a broad arc that, in general, follows the path of the Denali Fault along the Alaska Range and southwestward into the Yukon Territory. An ophiolite in the northwestern corner of British Columbia that is northeast of the projected Denali fault is included in this locality. A projection of the Denali fault system southwestward from the Alaska Range passes through the southwestern part of the Ahklun Mountains physiographic province, as the province was defined by Wahrhaftig (1965), to Kuskokwim Bay between the mouth of the Kuskowim River and Cape Newenham. Three mafic–ultramafic complexes on the southwestern edge of the Ahklun Mountains province are included in this domain. Glaciers covered this entire domain during the Pleistocene, and mountain glaciers and ice caps are still present at the higher elevations. Permafrost is currently discontinuous. The highest mountain in North America (Mt. McKinley, 6194 m) is in the Alaska Range, but the ultramafic rocks are all at much lower elevations. The climate is very cold throughout the domain, with severe winters and short summers. The mean annual precipitation ranges from 45 to150 cm in the Ahklun Mountains, from 30 to 60 cm in the Alaska Range, and from 30 to 75 cm, or more, in the Atlin area of northwestern British Columbia, which is in the rain shadow of the Coast Mountains. The greatest precipitation is during summers, from June or July to September or October. The frostfree period is on the order of 60–90 days, or shorter, but it may be longer in some of the Atlin area of British Columbia. Localities 9-1 through 9-3 are from Cape Newenham northeastward in the Ahklun Mountains. The ultramafic rocks in the Cape Newenham area were accreted to North America by north directed thrust faults during the Late Triassic and Middle Jurassic time. Localities 9-4 through 9-7 are in the Alaska Range. Locality 9-8 is along a projection of the Denali fault to the eastern edge of the Coast Ranges in British Columbia.