Conditions of the accumulation of organic matter and metals in the bottom sediments of the Chukchi Sea

Abstract

The chemical composition of bottom sediments in the Chukchi and, partly, East Siberian Seas was studied. In the south and west of the Chukchi Sea, a zone has been detected with the accumulation of sediments rich in organic carbon, an increased background content and anomalies of sulfophile metals (Mo, Zn, Hg, Ag, Au), iron-group metals (V, Ni, Co), and some PGE (Ru, Pt). This zone is confined to the neotectonic active system of rift troughs extending from the Bering Strait and eastern Chukchi Peninsula to the continental slope, where it is bounded by the Cenozoic Charlie rift basin of the Canadian hollow. The geochemical features of the carbon-enriched sediments evidence that they formed under oxygen-deficient conditions and, sometimes, in suboxic and anoxic environments near endogenic water and gas sources. The high carbon and metal contents suggest that the very fine-grained sediments in the rift troughs of the Chukchi Sea are a possible analog of some types of ancient highly carbonaceous sediments belonging to black shales.

Source, Origin, and Spatial Distribution of Shallow Sediment Methane in the Chukchi Sea

“…The average organic carbon content in the surficial sediments from the northern site is estimated to be 1.8%, with maximum values up to 2.38% in its southern and northern parts (Kolesnik and Mar'yash, 2011;Astakhov et al, 2013). Organic matter concentrations are related to sediment grain size and range from 0.05% in coarse-grained deposits to 2% in fine-grained sediments (Lysitsin, 1969;Walsh, 1989).…”

Chalcophile elements in black shales of the Bazhenov Formation, West Siberian sea basin

“…Thus, the low sedimentation rate determined not only the elevated total content of trace elements in the argillaceous-siliceous mudstones but also their contents with respect to their concentrators. Also, we might underestimate the role of organic matter in the concentration of trace elements, which might have been substantial (Astakhov et al, 2013;and others), and the more reducing regime of sedimentation and, then, diagenesis;…”

Sediment Geochemistry and Diatom Distribution in the Chukchi Sea: Application for Bioproductivity and Paleoceanography

“…The geochemistry of recent sediments in the Chukchi Sea has much in common with those in the other Arctic seas owing to their predominantly terrigenous origin under conditions of low runoff and low sedimentation rates (Kosheleva and Yashin, 1999;Viscosi-Shirley et al, 2003;Astakhov et al, 2013a). Unlike the other marginal seas of the Arctic Ocean, the Chukchi Sea is characterized by locally high primary productivity.…”

“…Preservation of biogenic elements and microfossils in shelf sediments depends not only on phytoplankton and benthic productivity but also on conditions that include sediment composition, seafloor relief, sedimentation rate, and geological structure ( Figure 1). Local depressions and gas and hydrothermal fluxes on the seafloor are common in areas with active geological processes, and they lead to increased anoxic bottom conditions that better preserve organic remains in sediments (Pedersen and Calvert, 1990;McKay and Pedersen, 2008;Astakhov et al, 2010Astakhov et al, , 2013a.…”

“…The Chukchi Sea's graben-rift system is bounded to the north by the Cenozoic Charlie rift basin ( Figure 1). Their geological relationships are unknown due to a lack of knowledge of the regional geology (Astakhov et al, 2013a).…”