Composition of bottom sediments from the Isfjord, Western Svalbard

Lithology, heavy mineral associations, and chemical composition of bottom sediments studied in two gravity cores from Isfjord, Western Spitsbergen (Svalbard) accompanied by high-frequency seismic records, provide a new insight on provenance and glaciomarine sedimentation in the fjord from the last deglaciation through Holocene.

Composition of sediments, rocks, and ores from the Northern and Equatorial Indian Ocean

The monograph has been written on the base of data obtained from samples and materials collected during the 19-th cruise of RV ''Akademik Vernadsky'' to the Northern and Equatorial Indian Ocean. Geological features of the region (stratigraphy, tectonic structure, lithology, distribution of ore-forming components in bottom sediments, petrography of igneous rocks, etc.) are under consideration. Regularities of trace element concentration in Fe-Mn nodules, nodule distribution in bottom sediments, and engineering-geological properties of sediments within the nodule fields have been studied. Much attention is paid to ocean crust rocks. The wide range of ore mineralization (magnetite, chromite, chalcopyrite, pyrite, pentlandite, and other minerals) has been ascertained.

Major nannofossils, carbon and oxygen isotopes and carbon composition of ODP leg 194 site survey gravity cores

Biostratigraphic, sedimentologic, and geochemical analyses of hemipelagic periplatform sediments from shallow gravity cores taken during the Ocean Drilling Program Leg 194 site survey reveal that, despite the strong currents and almost infilled intraplatform bathymetric depressions, recent sedimentation at the location of the Leg 194 drill sites recorded glacial-interglacial cycles. Sediment analyses included determination of sediment type, carbonate content, bulk stable oxygen isotope composition, and calcareous nannofossil zones. Glacial periods, identified by elevated bulk d18O, are characterized by darker sediment color, coarser grain size, and lower carbonate content, whereas interglacial periods yield lighter-colored, finer, and carbonate-rich sediments. These data from the shallowmost few meters of Marion Plateau sediments complement the subsurface information of Leg 194 holes, in which the top few meters have not been analyzed in such a high-resolution fashion. In addition, these gravity cores are more likely to have recovered the sediments closest to the sediment/water interface as compared to the hydraulic piston cores collected during Leg 194.

Organic compounds in snow, ice, and sub-ice waters from the mouth of the Severnaya Dvina River and the Kandalaksha Gulf (White Sea)

The paper reports data on concentrations of organic compounds (organic carbon, lipids; aliphatic hydrocarbons, and polycyclic aromatic hydrocarbons) in snow, ice, and sub-ice waters from the mouth of the Severnaya Dvina River in March 2005-2007 and the Kandalaksha Gulf (Chupa Bay) in March 2004. It was established that organic compounds are accumulated in snow and the upper ice layer near Archangelsk city. Distribution of molecular markers indicates that pollutions were mainly caused by local fallouts. In the Chupa Bay organic compounds are concentrated in the lower ice layer; it is typical for Arctic snow-ice cover. High contents of organic compounds in the snow-ice cover of the White Sea are caused by pollution of air and water during the winter season.

Calcium carbonate, isotopes and Rock-Eval pyrolysis at DSDP Holes 77-535 and 77-540

At DSDP Sites 534 (Central Atlantic) and 535 and 540 (Gulf of Mexico), and in the Vocontian Basin (France), Lower Cretaceous deposits show a very pronounced alternation of limestone and marl. This rhythm characterizes the pelagic background sedimentation and is independent of detritic intercalations related to contour and turbidity currents. Bed-scale cycles, estimated to be 6000-26,000 yr. long, comprise major and minor units. Their biological and mineralogic components, burrowing, heavy isotopes C and O, and some geochemical indicators, vary in close correlation with CaCO3 content. Vertical changes of frequency and asymmetry of the cycles are connected with fluctuations of the sedimentation rate. Plots of cycle thickness ("cyclograms") permit detailed correlations of the three areas and improve the stratigraphic subdivision of Neocomian deposits at the DSDP sites. Small-scale alternations, only observed in DSDP cores, comprise centimetric to millimetric banding and millimetric to micrometric lamination, here interpreted as varvelike alternations between laminae that are rich in calcareous plankton and others rich in clay. The laminations are estimated to correspond to cycles approximately 1,3, and 13 yr. in duration. The cyclic patterns appear to be governed by an interplay of continental and oceanic processes. Oceanic controls express themselves in variations of the biogenic carbonate flux, which depends on variations of such elements as temperature, oxygenation, salinity, and nutrient content. Continental controls modulate the influxes of terrigenous material, organic matter, and nutrients derived from cyclic erosion on land. Among the possible causes of cyclic sedimentation, episodic carbonate dissolution has been ruled out in favor of climatic fluctuations with a large range of periods. Such fluctuations are consistent with the great geographic extension shown by alternation controls and with the continuous spectrum of scales that characterizes limestone-marl cycles. The climatic variations induced by the Earth's orbital parameters (Milankovitch cycles) could be connected to bed-interbed alternations.

Concentration of organic compounds in slush, under-ice water, and the snow-ice fast-ice cover of the southeast sector of the Antarctic in April 2008

Data are presented on concentration of hydrocarbons (HC) relative to concentrations of suspended matter, lipids, organic carbon, and chlorophyll a in surface waters and snow-ice cover of the East Antarctic coastal areas. It was shown that growth of concentrations of aliphatic HC (AHC) to 30 µg/l in surface waters takes place in frontal zones and under young ice formation. AHC concentration in snow increases with growth of aerosol concentration in the atmosphere. In the lower part of ice, at the boundary with seawater, despite low temperatures, autochthonous processes may provide high AHC concentrations (up to 289 µg/l). Within the snow-ice cover on fast ice, concentration co-variations of all the compounds considered take place.

Composition of organic matter from water, suspended matter, and bottom sediments of Nha Trang Bay, South China Sea

This research has been carried out in the Nha Trang Bay (Southern Vietnam, South China Sea) at a section from the estuary of the Cai River to the marine part of the bay, as well as in the area of coral reefs. River- and sea waters, suspended matter, and bottom sediments are studies. Data on dissolved organic carbon and total nitrogen in water are obtained. Organic carbon concentration is estimated in suspended matter; organic carbon and molecular and group compositions of n-alkanes are determined in bottom sediments. Molecular and group compositions of n-alkanes in bottom sediments of the landfill made it possible to identify three types of organic matter (OM): marine, mixed, and mainly of terrigenous origin. All these types of OM are closely related to specificity of sedimentation and hydrodynamics of waters in this area.

Organic-geochemical and petrographical composition of sediments from ODP Leg 164 sites

Sediments from Holes 994C, 995A, 997A, and 997B have been investigated for "combined" gases (adsorbed gas and that portion of free gas that has not escaped from the pore volume during core recovery and sample collection and storage), solvent-extractable organic compounds, and microscopically identifiable organic matter. The soluble materials mainly consist of polar compounds. The saturated hydrocarbons are dominated by n-alkanes with a pronounced odd-even predominance pattern that is derived from higher plant remains. Unsaturated triterpenoids and 17ß, 21ß-pentacyclic triterpenoids are characteristic for a low maturity stage of the organic matter. The low maturity is confirmed by vitrinite reflectance values of 0.3%. The proportion of terrestrial remains (vitrinite) increases with sub-bottom depth. Within the liptinite fraction, marine algae plays a major role in the sections below 180 mbsf, whereas above this depth sporinites and pollen from conifers are dominant. These facies changes are confirmed by the downhole variations of isoprenoid and triterpenoid ratios in the soluble organic matter. The combined gases contain methane, ethane, and propane, which is a mixture of microbial methane and thermal hydrocarbon gases. The variations in the gas ratios C1/(C2+C3) reflect the depth range of the hydrate stability zone. The carbon isotopic contents of ethane and propane indicate an origin from marine organic matter that is in the maturity stage of the oil window.

Methane and microbiological processes in the Barents Sea

Biogeochemical cycle of methane in the Barents Sea was studied using isotope geochemistry to determine rates of microbial methane oxidation. It was established that microbiological processes (glucose consumption, 14CO2 assimilation, sulfate reduction, and slow methane oxidation) in oxidized surface and weakly reduced sediments are marked by only insignificant change in SO4 concentration and absence of notable increase of total alkalinity and N/NH4 downward sediment cores. Microbial methane productivity was 0.111x10**6 mol/day. Taking into account volume of the water column, microbial methane consumption therein can be as much as 1.8x10**6 mol/day.

Organic matter, isotopic composition of calcite veins in basement basalt and pore water at DSDP Leg 78A Holes

Sediments of the Barbados Ridge complex, cored on DSDP Leg 78A, contain low concentrations of acid-insoluble carbon (0.05-0.25%) and nitrogen (C/N 1.5-5) and dispersed C1-C6 hydrocarbons (100-800 ppb). The concentrations of organic carbon and 13C in organic carbon decrease with depth, whereas the concentration of dispersed hydrocarbons increases slightly with depth. These trends may reflect the slow oxidation of organic matter, with selective removal of 13C and slow conversion of the residual organic matter to hydrocarbons. Very minor indications of nitrogen gas were observed at about 250 meters sub-bottom at two of the drilling sites. Basement basalts have calcite veins with d13C values in the range of 2.0 to 3.2 per mil and d18O-SMOW values ranging from 28.5 to +30.6 per mil. Interstitial waters have d18O-SMOW of 0.2 to -3.5 per mil and dD-SMOW of -2 to -15 per mil. The oxygen isotopic composition of the calcite veins in the basement basalts gives estimated equilibrium fractionation temperatures in the range of 11 to 24°C, assuming precipitation from water with d18O-SMOW in the range of +0.1 to -1.0 per mil. This suggests that basalt alteration and precipitation of vein calcite occurred in contact either with warmer Campanian seawater or, later, with pore water, after burial to depths of 200- 300 meters. Pore waters from all three sites are depleted in deuterium and 18O, and dissolved sulfate is enriched in 34S at Sites 541 and 542, but not at Site 543.

Distribution, origin, and hydrocarbon-potential of organic matter in sediments from DSDP Leg 66 Holes

As part of an ongoing program of organic geochemical studies of sediments recovered by the Deep Sea Drilling Project, we have analyzed the types, amounts, and thermal alteration indices of organic matter collected from the Pacific continental margin of southern Mexico on Leg 66. The samples were pieces of core frozen aboard ship. Some of them were analyzed by pyrolysis, heavy C15+ hydrocarbons, and nonhydrocarbons to help determine their origin and hydrocarbon potential. Our main objectives were to find out how much organic matter was being deposited; to establish whether it derived from marine or terrestrial sources; to determine the controls of deposition of organic matter; to estimate the hydrocarbon potential of the drilled section; and to compare and contrast organic sedimentation here with that on other margins.