Mineralogy of sediments on the shelves of the Laptev and East Siberian Seas

Abstract

The Laptev and East Siberian Seas are the shallow landward extensions of the Arctic Ocean which borders mainland Siberia to the north. The Laptev and East Siberian seas receive sediments from the complex structural regions that comprise mainland Siberia. Mainland Siberia is characterized by a harsh continental climate yielding intense mechanical weathering and by the complex fluvial network that drains the area. Terrigenous sediments that reach the Laptev and East Siberian Seas are influenced and distributed by bathymetry, ice form-nation, and the current regime. The mineralogy, occurrence, and distribution of these recent sediments have been characterized by x-ray diffraction and by optical and electron microscopy. Quantification of the heavy mineral fraction was determined by point counting and semi-quantification of the clay fraction was determined through forward modeling via NEWMOD. The bottom sediments of the Laptev and East Siberian Seas ranged from black-dark brown -tan, massive to very finely laminated sandy silty clays, silty sandy clays, silty clays, and silty sands. Heavy minerals of the Laptev and East Siberian Seas are restricted to the continental shelves and nearshore areas and the typical heavy mineral assemblage consists of amphibole, augite, hypersthene, quartz, and epidote with varying amounts of the following heavy minerals: andalusite, apatite, garnet, kyanite, monazite, rutile, sphene, staurolite, tourmaline, zircon, zoisite, and opaque minerals. The typical clay mineral assemblage consists of varying amounts of illite, discrete smectite, mixed layer illite/smectite, kaolinite, chlorite, quartz and feldspar. These heavy mineral and clay mineral assemblages reflect, and are a direct product of the climate and intense fluvial transportation. These sedimentary and environmental factors enable heavy mineral and clay mineral analyses to provide valuable information as to the source and provenance lithologies of mainland Siberia as well as establish a set of baseline data for future investigations.