Speciation of metals in bottom sediments from the south Kara Sea and Ob and Yenisei estuarine zones

Speciation of Fe, Mn, Zn, Cu, Co, Ni, Cr, Pb, and Cd was studied in 52 samples of bottom sediments collected during Cruise 49 of the R/V "Dmitry Mendeleev" to the estuaries of the Ob and Yenisei rivers and to the southwest Kara Sea. Immediately after sampling the samples were subjected to on-board consecutive extraction to separate metal species according to their modes of occurrence in the sediments: (1) adsorbed, (2) amorphous Fe-Mn hydroxides and related metals, (3) organic + sulfide, and (4) residual, or lithogenic. Atomic absorption spectroscopy of the extracts was carried out at a stationary laboratory. Distribution of Fe, Zn, Cu, Co, Ni, Cr, Pb, and Cd species is characterized by predominance of lithogenic or geochemically inert modes (70-95% of bulk contents), in which the metals are bound in terrigenous and clastic mineral particles and organic detritus. About half of total Mn amount and 15-30% of Zn and Cu are contained in geochemically mobile modes. Spatiotemporal variations in proportions of the metal species in the surface layer of sediments along sub-meridional sections and through vertical sections of bottom sediment cores testify that Mn and, to a lesser extent, Cu are the most sensitive to changes in sedimentation environment. The role of their geochemically mobile species notably increases under reducing conditions.

Mineralogy, grain size composition, bulk carbonate isotopic ratios and ages of ODP Site 182-1128 sediments

This report presents mineralogic and geochemical data from Ocean Drilling Program Leg 182 Site 1128 in the Great Australian Bight. Clay mineralogy is dominated by mixed-layer illite-smectite, followed by minor amounts of kaolinite and illite, with intervals of pure smectite. Carbonate mineralogy is exclusively low-Mg calcite, except for one interval of dolomite in lower Oligocene sediments. Carbonate increases significantly in upper Eocene sediments, decreases through the lower Oligocene, then increases again in the Neogene. Quartz is present as a minor component that covaries inversely with carbonate. High-resolution sampling associated with Chron 13 normal (early Oligocene) reveals high-frequency (~23 k.y.) fluctuations in clay mineralogy and carbonate abundance and a positive oxygen and carbon isotope excursion (in bulk carbonates) related to Antarctic glaciation.

Calcium carbonate mineralogy and stable isotopic composition of Leg 182 sites, Great Australian Bight

An intensive stable isotopic investigation was conducted on sediments recovered from the Great Australian Bight during Ocean Drilling Program Leg 182 at Sites 1127, 1129, and 1131. The sites comprise a transect from the shelf edge to upper slope through a thick sequence of predominately Quaternary cool-water carbonate sediments. Detailed mineralogic and stable isotopic (d18O and d13C) analyses of sediments from a total of 306 samples are presented from all three sites.