Recent Sediments of the East Siberian Sea

Abstract

The East Siberian Sea, one of the large epicontinental arctic seas off northeastern Siberia, is shallow and covered with ice most of the year. The sea bottom is monotonously flat except where intersected by two drowned river valleys. The surficial sediments are fine grained, often containing over 15% colloidal (finer than 11o) material. This is attributed to mechanical weathering in the arctic permafrost region, the low gradients of incoming rivers, and the low energy conditions that exist in the East Siberian Sea. The primary sources of sediment are the Indigirka and Kolyma Rivers and the New Siberian Island region. Sediment transport is generally easterly to northeasterly. On the basis of factor analysis of grain-size data and heavy mineral analysis of the 4o sand fraction, three distinctive sediment groups have been defined within regions corresponding roughly to the western, central, and eastern portions of the East Siberian Sea. Sediment derived from the New Siberian Islands dominates the shallow (10 to 15 m) western region. Currents here are stronger than average and silt is the dominant sediment type. The central plateau is dominated by material introduced by the Indigirka River, characterized by low concentrations of heavy minerals. Currents here are generally weaker than in the New Siberian Shoal region and sediments are typically clayey-silts. Zones of cleaner silts indicate locally more intense currents. The eastern third of the East Siberian Sea is characterized by relatively deep (30 to 50 m) irregular topography, and variable sediment texture and mineralogy. Winnowed sandy sediments and gravelly-sandy-muds possibly associated with ice rafting break the pattern of silty-clays and clayey-silts. The Kolyma River has introduced most of the sediment into this region, although local shore line sources are indicated clearly by the mineralogy. Ice rafting generally appears to be insignificant in the East Siberian Sea sediments.