Notes on the geology of the St. Elias Range, Alaska-Yukon Territory, North America

Abstract

The following notes are a preliminary record of geological results of work in the Yukon-Alaska boundary region by the writer with the expedition of the Arctic Institute of North America (project " Snow Cornice ") during the summer of 1949. Field-work was mainly along the northern border of the great inter-montane basin occupied by the Seward Glacier (or firn-field), which lies intrenched behind, and immediately north of, the main St. Elias Range, of which Mt. St. Elias itself, 18,008 feet, is the dominant peak. During flights from the coast at Yakutat to and from this basin, and on other occasions over neighbouring localities, visual observations of structure and morphology were also made. Chiefly, however, field-work was a matter of climbing (as in the case of a pioneer ascent of Mt. Vancouver, 15,800 feet), or of skiing over the immense spaces of the Seward firn-field (750 square miles in area) in order to visit scattered island outcrops or mountain cliffs flanking the firn-field. The region is underlain by a metamorphic series of sedimentary origin, mainly pelitic, with subordinate psammitic elements and marked calc beds. The pelitic series consists mostly of biotite-schists and gneisses, rarely garnetiferous; the calc beds are composed of fairly pure marbles, which occupy no regular stratigraphical position within the pelites, but occur in mountain walls as conspicuous elongated or irregular masses, having suffered severe deformation during orogenesis. The thickness of this whole series, whose dip is variable and locally vertical, was not determinable. Into the series has been