Total organic carbon, metal concentrations and metal and aluminium ratios in bulk sediment from the ODP sample 169-1033B-4H-4,54-74

Holocene laminated sediments in Saanich Inlet, British Columbia, are interrupted by frequent, non-laminated, massive layers. These layers may be debris flows released by earthquakes or bioturbated sediments deposited during periods of relatively high bottom water oxygen concentration and/or low surface productivity, or both. We determined the organic carbon content and the concentration of a suite of redox-sensitive metals in bulk sediments at approximately 1-cm resolution across a laminated-massive-laminated interval (ODP Leg 169S Sample 1033B-4H-4,54-74), to determine the redox conditions under which the massive layer was deposited. Our results indicate that this massive interval was deposited under anoxic bottom waters. Manganese/Al ratios are consistently low throughout the massive section, while Mo/Al, Cd/Al, Re/Al, and U/Al ratios are enriched relative to their metal/Al ratios in detrital material (represented by Cowichan River suspended sediments). The concentration of organic carbon in the lower portion of the massive layer is higher than in the upper portion, which has a concentration similar to that in the overlying and underlying laminated sediments. Well-defined peaks in Mo/Al, Cd/Al, and Re/Al and a broad peak in U/Al occur in the lower portion of the massive layer. The positions of the Cd/Al, Re/Al, and Mo/Al peaks, as well as the increase in organic carbon content with depth in the massive layer, are best explained by a process of diagenetic redistribution of metals that occurred after the massive layer was emplaced.

Palynology from surface sediment samples of the Arctic Ocean

Freshwater chlorophycean algae are characteristic organic-walled microfossils in recent coastal and shelf sediments from the Beaufort, Laptev and Kara seas (Arctic Ocean). The persistent occurrence of the chlorophycean algae Pediastrum spp. and Botryococcus cf. braunii in marine palynomorph assemblages is related to the discharge of freshwater and suspended matter from the large Siberian and North American rivers into the Arctic shelf seas. The distribution patterns of these algae in the marine environments reflect the predominant deposition of riverine sediments and organic matter along the salinity gradient from the outer estuaries and prodeltas to the shelf break. Sedimentary processes overprint the primary distribution of these algae. Resuspension of sediments by waves and bottom currents may transport sediments in the bottom nepheloid layer along the submarine channels to the shelf break. Bottom sediments and microfossils may be incorporated into sea ice during freeze-up in autumn and winter leading to an export from the shelves into the deep sea. The presence of these freshwater algae in sea-ice and bottom sediments in the central Arctic Ocean confirm that transport in sea ice is an important process which leads to a redistribution of shallow water microfossils.

Nd, Sr and Pb isotopes and clay minerals in sediment cores from the Gulf of Cadiz and the Portuguese margin

The assemblages of marine sediments on the SW Iberian shelf have been controlled by contributions from distinct sources, which have varied in response to environmental changes since the Last Glacial Maximum (LGM). The rapid, decadal scale Mediterranean overturning circulation permits mixing of suspended particles from the entire Mediterranean Sea. They are entrained into the suspended particulate matter (SPM) carried by Mediterranean Outflow Water (MOW), which enters the eastern North Atlantic through the Strait of Gibraltar and spreads at intermediate depths in the Gulf of Cadiz and along the Portuguese continental margin. Other major sediment sources that have contributed to the characteristics and budget of SPM along the flow path of MOW on the SW Iberian shelf are North African dust and river-transported particles from the Iberian Peninsula. To reconstruct climate- and circulation-driven changes in the supply of sediments over the past ~23000 cal yr B.P., radiogenic Nd, Sr and Pb isotope records of the clay-size sediment fraction were obtained from one gravity core in the Gulf of Cadiz (577 m water depth) and from two gravity cores on the Portuguese shelf (1745 m, 1974 m water depth). These records are supplemented by time series analyses of clay mineral abundances from the same set of samples. Contrary to expectations, the transition from the LGM to the Holocene was not accompanied by strong changes in sediment provenance or transport, whereas Heinrich Event 1 (H1) and the African Humid Period (AHP) were marked by significantly different isotopic signatures reflecting changes in source contributions caused by supply of ice rafted material originating from the North American craton during H1 and diminished supply of Saharan dust during the AHP. The data also reveal that the timing of variations in the clay mineral abundances was decoupled from that of the radiogenic isotope signatures.

Mineralogy of northern Indian Ocean surface sediments and of suspended sediments of Indian rivers (Table 2 and 5)

The solid phases from surface sediments, atmospheric dusts, and rivers of the Indian Ocean environment have been analyzed for their clay minerals and quartz. Such data have been used to delimit the transport paths and sources of the detrital minerals in the oceanic deposits. Diagnostic in distinguishing fluvial and eolian inputs to the northern Indian Ocean is a combination of the clay mineral assemblages and of their geographic distributions. River borne solids are the primary components of the Bay of Bengal deposits. The eastern part receives its continental input through the Ganges-Brahmaputra river system, while drainage of the Indian Peninsula by rivers introduces solids to the western part. The former materials are characterized by high illite and chlorite in the clay mineral assemblages; the latter by montmorillonite. The winds over the Bay bear distinctive dust burdens based upon their directions. However, their contributions to the sediments are insignificant. The eastern sector of the Arabian Sea receives major contributions of continental debris from the rivers and the high montmorillonite levels clearly indicate a source in the Indian Peninsula. The rest of the Sea appears to receive most of its land-derived materials from the north, perhaps the desert regions of northern India and West Pakistan, and they are wind-borne. These materials are also transported to the equatorial regions of the Indian Ocean. A gradient in attapulgite, just north of the equator, may indicate an eolian contribution to the Arabian Sea from the African continent. The halogenated hydrocarbon pesticides were assayed in the southwest monsoon winds and enter the Bay of Bengal at levels of a half ton per month, an amount comparable to those introduced by other wind and river systems to the marine environment.

Geochemical and biogeochemical parameters of Black Sea waters and suspended matter

The monograph focuses on the analysis of data addressing the problem of H2S contamination and oxic-anoxic interface in the Black Sea. Regularities of the fine structure of vertical distribution of oxygen, hydrogen sulfide, biogenic elements, organic substances, suspended matter, and metals of the iron-manganese group in the area of contact of aerobic and anaerobic waters have been revealed. Also effects of biochemical, physico-chemical and dynamic processes on their vertical distribution have been examined. Sulfate reduction in seawater and bottom sediments has been studied. Quantitative estimates of H2S fluxes at the water - bottom sediment and O2-H2S interfaces have been done. Features of H2S oxidation have been studied, its budget in the Black Sea has been calculated. Multiyear spatial-temporal variability of the oxic-anoxic interface has been investigated.