Age marks in bottom sediments of the Pacific Ocean

Distribution of K-Ar age marks in Pacific bottom sediments is shown on the base of large analytical material. Dependence of K-Ar age marks on abundance of potassium-bearing authigenic diagenetic minerals (glauconite, phillipsite) widely spread in the studied part of the World Oceans.

Composition of suspended matter and bottom sediments from the Atlantic Ocean and its seas

The book summarizes data on distribution and composition of sedimentary material suspended in waters of the Atlantic Ocean and its seas. Results of observations of Soviet and foreign expeditions are given. Distribution of suspended matter in sections across the ocean, as well as in the most studied seas are shown. New data on grain size, mineral and chemical composition of suspended matter are published. Summary of history of investigation of bottom sediments from the Atlantic Ocean from the first scientific cruises to the present is done. A brief description of sediment types in the ocean and a detailed description of Mediterranean Sea sediments are given.

Sulfur speciation in bottom sediments from deep-sea basins of the Atlantic Ocean

Distribution of reduced sulfur forms in vertical sediment sections in deep-sea basins of the Atlantic Ocean is under study. Presence of weak sulfate reduction process resulted from low concentrations of reactive organic matter and differing by characteristic features of the initial stage of development. Interpretation of results is given on the base of consideration of dynamic redox equilibrium in the system: reduced sulfur - dissolved oxygen.

Organic matter in bottom sediments of the Northeast Pacific

The book is devoted to study of diagenetic changes of organic matter and mineral part of sediments and interstitial waters of the Pacific Ocean due to physical-chemical and microbiological processes. Microbiological studies deal with different groups of bacteria. Regularities of quantitative distribution and the role of microorganisms in geochemical processes are under consideration. Geochemical studies highlight redox processes of the early stages of sediment diagenesis, alterations of interstitial waters, regularities of variations in chemical composition of iron-manganese nodules.

Composition and accumulation rates of bottom sediments from Core ASV16-1372, Voring Plateau

Based on sedimentological, mineralogical, geochemical, and micropaleontological data on comprehensively investigated Core ASV16-1372, Late Pleistocene - Holocene sedimentation history is reconstructed for the Voring marginal plateau (continental margin of the Norwegian Sea). An age model constructed is based on correlation with several adjacent cores, for which AMS radiocarbon datings are available. Lithostratigraphic correlation made it possible to compare stratigraphic division of Core ASV16-1372 with other cores sampled on the Voring Plateau and the shelf and continental slope off Central Norway. It is concluded that compositional and structural features of bottom sediments are correlated with paleoclimatic and paleoceanographic changes, variations in provenances, as well as agents and pathways of sedimentary material transport.

Composition of bottom sediments from the Campeche Bank

A complete section of an unconsolidated sedimentary sequence about 5 m thick was sampled in the western margin of the Campeche Bank with use of gravity cores. The sequence forms a flat sea bottom at depth of 51-53 m and rests on a consolidated basement composed of coral limestones and carbonate sandstones. Initiation of deposition of unconsolidated sediments in this area is related to a sea transgression caused by sea level rise that followed the Würm glaciation stage about 10-11 ky ago. Analysis of grain size and chemical compositions of sediments and study of biogenic carbonate remains made it possible to outline environmental changes in this region during the last 10 ky.

Chemical composition of Black Sea bottom sediments

Concentrations of major-, trace- and rare earth elements in recent and Old Black Sea bottom sediments are reported in the paper. Data presented suggest that accumulation of black shale deposits was not constrained to a certain time span but proceeds in certain modern basins and generates sediments with metal contents close to those in their ancients analogues in hydrogen sulfide contaminated environments. If REE are involved in the process, their composition can vary depending on such factors as variations in redox conditions and occurrence of phosphate and barite nodules, which can induce development of either positive or negative Eu anomalies.

Composition of bottom sediments from Core SO201-2-101, Shirshov Ridge, Bering Sea

Analysis of lithology, grain-size composition, clay minerals, and geochemistry of Upper Pleistocene bottom sediments from the submarine Shirshov Ridge (Bering Sea) showed that the Yukon-Tanana terrane of the Central Alaska was main source area of the sediments. Sedimentary material was transported by the Yukon River through Beringia up to the shelf break, where they were entrained by a strong north-west sea current. Lithological data revealed several pulses of ice-rafted debris deposition roughly synchronous with Heinrich events and periods of weaker bottom current intensity. Based on geochemical results we distinguished intervals of an increase in paleoproductivity and extension of the oxygen minimum zone. Our results suggest that there were three stages of deposition driven by glacioeustatic sea-level fluctuations and glacial cycles in Alaska.

Radiocarbon age and sedimentation rates of bottom sediments in the Obskaya Gube (Ob River estuary

Complex geological-geochemical studies of water column and bottom sediments were carried out during Cruise 49 of R/V "Dmitry Mendeleev" in the Kara Sea shelf zone along the Obskaya Guba (Ob River estuary) from the Pur River and Taz River mouths to 76°N. Carbon-14 concentrations in organic matter from bottom sediments were determined at 5 stations. Constant initial 14C concentration model was used to determine sedimentation rates that were taken as a basis for calculating ages of sediment cores and their separate parts and for inferring location of a depocenter, i.e. a region of maximal discharge of fine-dispersed fraction of suspended matter of river run-off. Sedimentation rate in the depocenter is 170 cm/ka. Southward moves of the depocenter were recorded for periods of sea-level rises 2 and 5 thousand years ago. Bottom sediments in the depocenter contain 45% of organic matter primary produced in the Obskaya Guba. This organic matter is an energetic basis for bottom fauna life. About 55% of organic matter comes with river run-off.