Composition of bottom sediments from the Central Basin of the Indian Ocean

A study of petrographic and mineral compositions of 26 sediment cores from the western part of the Central Basin of the Indian Ocean has identified biogenic, terrigenous, volcanogenic, and authigenic sediment types formed in certain facies conditions. On the basis of bio- and paleomagnetic stratigraphy data from the cores sedimentation rates of different sediment types have been calculated. Modern and Pliocene-Pleistocene positions of the main facies boundaries (the critical depth of carbonate accumulation, the geochemical boundary between hemi- and miopelagic zones, the frontal boundaries of the equatorial belt of biogenic silica accumulation) have been determined. It has been shown that the sedimentary process during Pliocene-Quaternary had cycle variations characterized by successive changes of different sedimentation types - hemipelagic, miopelagic, and biogenic.

Planktonic foraminiferas in bottom sediments and Late Quaternary paleotemperatures of surface waters in the North Tropical Atlantic

Distribution of planktonic foraminiferal tests was studied in 15 Upper Quaternary sediment cores from the continental slope of Africa, the Canary and Cape Verde basins, and slopes of the Mid-Atlantic Ridge. In all the cores substantial variations were found in relationship between foraminiferal planktonic species reflecting fluctuations of mean annual temperatures of surface waters. Temperature difference in temperatures between present time and that of the maximum of the stadial of the last continental glaciation glacial stadial (about 18,000 yrs ago) ranges from 8.5°C in the Canary upwelling region to minimum values of 2.0°C in the central part of the ocean, i.e. the southern part of the subtropical gyre. Temperature difference the Holocene optimum and 18,000 yrs ago ranges from 10°C to 3°C. Age estimates are supported by radiocarbon dates.

Chemical composition of bottom sediments and rocks from DSDP Holes 3-14 through 64-477

Data on analyses of chemical composition of DSDP samples of bottom sediments and rocks carried out in P.P. Shirshov Institute of Oceanology are reported. Basal sediments and sedimentary rocks prevail in the sample set.

Chemical composition of basalts from coarse debris of the Kara Sea bottom sediments

Study of basaltic debris from the Kara Sea bottom has shown its similarity to traps of the Eastern Siberia in mineralogy, structures and chemical composition. In comparison with oceanic tholeiites, the source of traps and Kara Sea basin basaltic melts was enriched in REE and some other incompatible elements. K-Ar dating of two samples of supposed autochtonous location from the eastern part of the Kara Sea basin has shown 209 and 218 Ma - younger than traps (247-248 Ma). Origin of Siberian traps used to connect with action of the mantle plume (Iceland plume, according to geodinamic reconstruction). Our new age data may be interpreted as an evidence of the Siberian plate moving over the head of plume.

Microfossils and chemical elements in bottom sediments of the Ashadze-1 Hydrothermal Field (tropical Mid-Atlantic Ridge)

The first thorough analysis of microfossils from ore-bearing sediments of the Ashadze-1 Hydrothermal Field in the Mid-Atlantic Ridge sampled during Cruise 26 of R/V Professor Logachev in 2005 revealed substantial influence of hydrothermal processes on preservation of planktonic calcareous organisms as well as on preservation and composition of benthic foraminifera. From lateral and vertical distribution patterns and secondary alterations of microfossils it is inferred that the main phase of hydrothermal mineralization occurred in Holocene. Heavy metals (Cu, Co, Cr, and Ag) were accumulated by foraminiferal tests and in their enveloping Fe-Mn crusts. Distribution of authigenic minerals replacing foraminiferal tests demonstrates local zoning related to hydrothermal activity. There are three mineral-geochemical zones defined: sulfide zone, zone with elevated Mg content, and zone of Fe-Mn crusts.

Chemical element contents and speciations in bottom sediments from the Transpacific profile

The paper deals with regularities of distribution of iron, manganese, copper, nickel, and vanadium in interstitial waters from different lithofacies types of bottom sediments on the profile from the coast of Mexico to the Wake Atoll in the Pacific Ocean. With increasing distance from the shore and with transition from reduced coastal sediments to oxidized deep-sea red clays concentration of iron and manganese in the interstitial waters greatly decreases. Elevated concentration of dissolved iron (0.34 mg/l) was observed only in highly reduced terrigenous sediments from the shelf and continental slope of Mexico. The highest concentrations of manganese (13.2 mg/l) were measured in hemipelagic carbonate-siliceous-clayey sediments. Compared to Pacific seawater interstitial waters are enriched in Fe, Mn, Cu, Ni, V. Interstitial waters contain only from 0.000004 to 1.2% of total contents of these elements in bottom sediments.

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.