The description of late Pleistocene and Holocene deglaciation and environments in the Copper River–Chugach Mountains region is based on surficial geology as well as on pollen analysis and radiocarbon dating of core samples. The results of this study indicate that late Pleistocene glaciers extended well beyond the present coastal plain. Deglaciation began in the lower Copper River valley prior to 14,000 yr B.P. and in the Bremner and Tasnuna River valleys about 10,000 and 9000 yr B.P., respectively. Cirque glaciers formed marginal moraines at an elevation of ∼560 m in the Tasnuna Valley ∼8800 yr B.P. On the basis of the pollen record, shrub-herb tundra characterized the initial late wisconsinan vegetation. Tundra was succeeded first by alder-dominated vegetation and then by spruce forest. The late-glacial pollen zones indicate a time-transgressive colonization of the river valleys and mountain slopes inland from the coast.

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