Chemical composition of sediments from the Indian Ocean

Intensive reduction processes within bottom sediments from the Bay of Bengal lead to marked enrichment of the oxidized layer in iron and manganese. This is not observed in sediments from the Arabian Sea. Oxidized bottom sediments in central areas of the Indian Ocean show high iron concentrations, but fraction of reactive Fe in total Fe is lower. Manganese concentration increases steadily with distance from the shore to the pelagic region of the ocean, and fraction of reactive manganese also increases in the same direction. There is close correlation between total Mn and Mn(4+) in these sediments.

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.

Chemical and mineral compositions of basalts from the Pacific Ocean, DSDP data

Mineral and chemical alterations of basalts were studied in the upper part of the ocean crust using data of deep-sea drilling from D/S Glomar Challenger in the main structures of the Pacific floor. Extraction of majority of chemical elements (including heavy metals) from basalts results mainly from their interaction with heated sea water. As a result mineralized hydrothermal solutions are formed. On entering the ocean they influence greatly on ocean sedimentation and ore formation.