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Depositional Environments and Sediment Characteristics of the Colville and Adjacent Deltas, Northern Arctic Alaska
Polar deltas, typified by those on Alaska's North Slope, which have their drainage basins totally in the permafrost region and discharge into a polar sea, are significantly different from lower latitude deltas. In the arctic, features classically related to delta-front platform and slope facies are not well defined and certain continental facies are either nonexistent or less well developed. Except during occasional storms the North Slope deltas are exposed to low energy hydraulic conditions.
Mean size is the only textural parameter that can be used to differentiate sediments of the estuary, lagoon, coastal beach, bay and open marine environments. Except for coastal plain and beach deposits, the deltaic sediments are poorly to very poorly sorted silty sands or sand-silt-clays that have nearly symmetrical to positive-skewed size distributions. The coastal plain is comprised of tundra with associated permafrost, as well as gravels derived from underlying Quaternary material. The coastal beach foreshore consists of moderately to poorly sorted sands or gravelly sands that have nearly symmetrical to positive-skewed size distributions. The transport of gravels by ice-rafting is insignificant. Forty-three percent of the fluvial discharge occurs during three weeks in the spring and is in the form of an overflow on sea ice. Lack of discrete heavy mineral laminae reflect a lack of intense hydraulic sorting.
Terrigenous input primarily determines the clay mineral assemblage at any locality in the river. However, differences between fluvial and marine deltaic environments are discernible. Broad facies variations within the nearshore materials suggest that clay mineral suites may be of use in explaining sediment transport directions.
Differences in the chemistry of arctic and lower latitude deltaic sediments are recognizable as well as are variations among the subfacies of the arctic deltas.
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