Surficial geology and morphology of the Alaskan central Arctic coastal plain

Abstract

Mapping and analyses have defined the distribution, morphology, character, and age of marine, fluvial, glacial, eolian, and lacustrine sediments of the late Cenozoic Gubik Formation in approximately 12,000 km$\sp2$ of the Alaskan central Arctic Coastal Plain, and allowed interpretations of the depositional, climatic, and tectonic histories. Amino-acid analysis of wood and some shell materials has defined broad age groups: young, middle and old. The old group has been abandoned because of probable leaching of acids or other modification. These groups are the basis for correlation of deposits between areas and have been assigned minimum relative ages. The young group is at least Sangamonian and the middle group is probably at least middle Pleistocene. Notable among interpretations of the surficial geology and morphology are: (1) Transgression of early Wisconsinan and perhaps Sangamonian seas as far as 9 km inland from the present coast. (2) Tertiary glacial advances as far north as uplands near Kavik airstrip and perhaps the headwaters of the Kachemach and Miluveach Rivers. (3) Three marine terraces as old as middle to late Pliocene and three late Pleistocene alluvial terraces east of the Colville River. (4) Middle Pleistocene minimum age for the Ugnuravik gravel is indicated by wood of the middle amino-acid group. (5) Coexistence of coniferous and nonconiferous wood on the Coastal Plain in middle to early Pleistocene time is possibly explained by greater accumulation of summer warmth associated with a continental climate resulting from greater exposure of the continental shelf. (6) Late Pliocene through Pleistocene outwash and alluvium and Holocene alluvium compose the Canning gravel. (7) Folding of the Coastal Plain in western ANWR and up to 95 m of uplift in the Sadlerochit Mountains since latest Pliocene time. (8) Late middle through late Wisconsinan age for the Beechey sand. (9) Late Wisconsinan through early Holocene age for thaw lakes in which broad-based mounds formed. While other findings and interpretations may be less significant, collectively they have allowed a start toward definition of the surficial geology.