Organic and carbonate carbon in permafrost and thawed deposits from Buor-Khaya Bay (Laptev Sea)

Doklady Earth Sciences - The distribution of organic and carbonate carbon in core samples from holes drilled in the shallow part of the Laptev Sea, in the region of Buor-Khaya Bay and Bykovskii...     

Particle size composition of Holocene–Pleistocene deposits of the Laptev Sea (Buor-Khaya Bay)

New data on the particle size composition of the Laptev Sea shelf deposits were obtained on the basis of results of low-angle laser light-scattering of core samples from the columns studied. It was revealed that the sand fraction dominates. The results of comparative analysis of the particle size composition of deposits show that the Laptev Sea shelf zone was characterized by highly variable spatial–temporal conditions and settings of sedimentation in the Quaternary, a polygenic character of deposits, and a pulsating influence of fluvial and slope processes on the conditions of sedimentation. A tendency of coarsening in the vertical sequence that contributes to thawing of the permafrost was revealed in the Ivashkina lagoon.     

Genesis of organic matter in the Kara Sea bottom sediments

Based on simultaneous use of organic and geochemical indicators (δ¹³C, C/N, and n-alkanes), the genesis of organic matter (OM) in recent bottom sediments of the Kara Sea was characterized. Maps for percentages and absolute masses of marine and terrigenous OM were drawn. The masses of buried marine and terrigenous OM were compared to its supply to the sea and onto the sea bottom.     

Carbohydrates as indicators of biogeochemical processes

A method is presented to study the carbohydrate composition of marine objects involved into sedimento- and diagenesis (plankton, particulate matter, benthos, and bottom sediments). The analysis of the carbohydrates is based upon the consecutive separation of their fractions with different solvents (water, alkali, and acid). The ratio of the carbohydrate fractions allows one to evaluate the lability of the carbohydrate complex. It is also usable as an indicator of the biogeochemical processes in the ocean, as well of the genesis and the degree of conversion of organic matter in the bottom sediments and nodules. The similarity in the monosaccharide composition is shown for dissolved organic matter and aqueous and alkaline fractions of seston and particulate matter.     

Alkanes in Quaternary deposits of the Laptev Sea

The distribution and genesis of n-alkanes in sediments from the 38-m sequence obtained during core boring in the Ivashkina lagoon were studied. Sediments were formed in the Holocene as a result of thermokarst and penetration of seawater. The sequence mostly includes permafrost rocks partially molten in the upper horizons and covered by Quaternary deposits, which are mostly the products of thermoabrasion.     

Organic matter of the World Ocean

Available data on synthesis, input, and decomposition of organic matter (OM) in the water column and recent bottom sediments of the World Ocean are generalized. The most reliable values of OM production and masses in the ocean, the total supply of organic carbon, and the input of terrigenous OM with coastal erosion, river runoff, and eolian matter are estimated. Maps of fossilization coefficients, distribution, and accumulation of OM in recent bottom sediments of the World Ocean are presented. A numerical expression is proposed for the main circumcontinental pattern of OM accumulation in the ocean. The group and elemental compositions of living matter of the ocean, land, and the Earth as a whole and the organic composition of bottom sediments are briefly considered.     

Lignin as an indicator of the sedimentation conditions on the Arctic shelf

It is shown for the first time that the proportion of lignin in shelf deposits may range from 1/3 to the total concentration of organic carbon. The distribution of wood residues and lignin in the studied sedimentary formation is very uneven, which reflects the dynamic flux environment of sedimentation and OM supply. The calculated molecular indexes showed that most of the OM in deposits underwent insignificant diagenetic alterations.     

Polycyclic aromatic hydrocarbons in Holocene–Pleistocene sediments of the Laptev Sea

The distribution and genesis of polycyclic aromatic hydrocarbons (PAHs) were studied in a 40-m core from a lagoon of the Laptev Sea that appeared during the Holocene resulting from the flooding of seawater into a freshwater lake in the area of the Buor-Khaya Gulf. The bulk of the core is constituted of permafrost rocks, thawed partially in their upper layers and covered with recent sediments (mainly by the products of intense thermoabrasion). The ratio of petrogenic and pyrogenic PAHs was evaluated.