Phytoplankton fluxes and biomass in the White Sea in 2007 and 2008

Vertical fluxes of phytoplankton (VF_phyto) and particulate organic carbon (VF_POC) in the White Sea were determined using seven long-term (292 to 296 days) sediment traps moored at five stations at depths 67 to 255 m. Annual VF_phyto and VF_POC ranged from 0.55 to 24.64 g C/m**2 and from 3.7 to 93.9 g C/m**2, respectively. The highest VF_phyto was observed in the Basin region located close to the Gorlo along the Tersk coast. Algal biomass accounted for 15-43% of VF_pOC. Diatoms comprised the most important group accounting for 83-100% in sinking biomass. Thalassiosira nordenskioeldii dominated in VF_phyto at all trap stations except for one in the Basin close to the Onega Bay, where Ditylum brightwellii was the most abundant.

Composition of Lower Cretaceous sandstones of the Galicia margin

The composition of 31 samples of Lower Cretaceous (Valanginian to Aptian) sandstone from ODP Sites 638 through 641 was analyzed using the Gazzi-Dickinson point-counting method. The results show that the source of the Valanginian to Hauterivian sand was a continental block, dominated by granitic and/or high-grade-metamorphic rocks. Although these petrologic results do not allow discrimination between various potential continental block provinces, they suggest, in conjunction with seismic profiles and regional considerations, that the source was the Galicia margin or western Iberia. In contrast, the Barremian and Aptian sand is dominated by carbonate grains that were derived from a carbonate platform, probably on Galicia Bank.

Occurrence of mammalia relicts at site Nörre-Lyngby

Investigations at a Late Weichselian freshwater basin in northwestern Jutland, Denmark, yielded a fairly rich assemblage of vertebrate remains, mostly bones and teeth of small mammals. The remains are primarily allochthonous and the bones have been subjected to different taphonomic pathways and agents. AMS 14C-dates on terrestrial organic remains provided ages of Middle to Late Allerød time. Identifications revealed the first fossil record in Scandinavia of Rana arvalis, Sorex minutus, Ochotona cf. pusilla, Microtus gregalis, Microtus oeconomus, and Sicista cf. betulinu. Spermophilus cf. major and Desmana moschata, previously found only once and twice respectively, were retrieved, and Sorex araneus and Arvicola terrestris were recovered for the first time beyond the Atlantic chronozone. Ecologically, the Nørre Lyngby small mammal fauna can be characterized by its very high and almost equal proportions of boreal forest and steppe elements followed by a relatively high proportion of tundra elements. The fossil species share a modern area of sympatry north of the Caspian Sea from the river Volga in the west to the southern and western slopes of the Urals. If, however, the large Allerød mammals are added, the fauna is without modern analogues. The Nørre Lyngby fauna can be seen as a last expansion of the North European glacial fauna. Provided that an absolute chronology and a differentiated sea-level curve for the area can be established, the Nørre Lyngby fauna could become important for studies in mammalian dispersal and migration rates.

(Table 1) Concentrations of particulate organic carbon in the South Atlantic in February-March 1989

On the basis of 332 analyses of dissolved (DOC) and particulate organic carbon (POC) in samples collected from the surface to 4785 m depth at 10 stations in the atlantic part of the Antarctic Ocean the following regularities were observed: low DOC concentration, a sharp decrease in upper 40-120 m, small changes deeper in the water column, decrease in concentrations in the Antarctic divergence zone, absence of a correlation between DOC and primary production of plankton. Decrease in POC concentrations with depth when there is a small gradient in the 0-200 m water layer, increase in POC concentrations in the pycnocline and during phytoplankton bloom were found. As a whole the Antarctic Ocean is characterized by small POC concentrations close to average values for the world ocean. The nature of DOC and POC concentrations changes in the surface layers of the Indian and Atlantic oceans along the ship's route was considered.

Compositional and isotopic data on core MD84641

The organic carbon isotopic record of the sapropels(S1 and S3-S10) and intercalated marl oozes has been determined in a 12-m piston core from the eastern Mediterranean. The d13C_organic values are systematically lighter (mean=-21.0±0.82 per mil) in all sapropels and heavier (mean=-18.8±1.07 per mil) in the marl oozes. These differences are not due to variable marine and terrestrial organic matter mixtures because all values are heavier than modern plankton in the Mediterranean, there is no relationship between the C_organic/N ratios and the isotopic values, and published information on the abundance and distribution of organic biomarkers shows that terrestrial material constitutes a minor fraction of the total organic matter. Temperature effects on isotope fractionation are also discounted because the change in d13C_organic values between glacial and interglacial horizons is in the opposite sense. Diagenesis, which can produce relatively small changes in the carbon isotopic composition of sedimentary organic matter under certain circumstances, is unlikely to have caused the observed differences because this mechanism would cause an enrichmet in 12C, implying that all values were even heavier originally, and there is no secular trend in the d13C_organic record. The observed differences in d13C_organic between the two lithologies are probably produced by changes in the isotopic composition and the concentration of dissolved CO2. First, freshwater flooding during the formation of the sapropels caused the isotopic composition of the dissolved inorganic carbon in the surface waters of the Mediterranean to become lighter because of the 13C deficiency in fresh waters. Hence photosynthesis would have produced isotopically lighter organic material. Second, changes in atmospheric pCO2 between glacial and interglacial periods, as shown by the Vostok ice core, caused marked changes in the concentration of free dissolved CO2 in the mixed layer; lower values during glacial maxima caused a smaller fractionation of the carbon isotopes by phytoplankton, whereas levels were less limiting during the interglacials. Concentrations of dissolved CO2 could also have been much higher during the deposition of the sapropels because of the supply of regenerated CO2 to the mixed layer by upwelling, and this could have further lightened the d13C_organic values in the sapropels themselves. Carbon isotope records may provide an alternative method for estimating atmospheric pCO2 levels over longer time periods than can be obtained from ice cores.

Organic geochemistry records from two Palaeocene-Eocene Thermal Maximum sections in Denmark

Analysis of sediments deposited at different latitudes around the world during the Palaeocene-Eocene Thermal Maximum (PETM; ~56 Ma) have revealed a globally profound warming phase, regionally varying from 5-8 °C. Such records from Europe have not yet been obtained. We studied the variations in sea surface and continental mean annual air temperatures (SST and MAT, respectively) and the distribution patterns and stable carbon isotopes of higher plant derived n-alkanes in two proximal PETM sections (Fur and Store Bælt, Denmark) from the epicontinental North Sea Basin. A negative carbon isotope excursion (CIE) of 4-7 per mil was recorded in land plant derived n-alkanes, similar to what has been observed for other PETM sections. However, differences observed between the two proximal sites suggest that local factors, such as regional vegetation and precipitation patterns, also influenced the CIE. The presence of S-bound isorenieratene derivatives at the onset of the PETM and increased organic carbon contents points to a rapid shift in depositional environment; from well oxygenated to anoxic and sulfidic. These euxinic conditions are comparable with those during the PETM in the Arctic Ocean. SSTs inferred from TEX86 show relatively low temperatures followed by an increase of ~7 °C across the PETM. At the Fur section, a remarkably similar temperature record was obtained for MAT using the MBT'/CBT proxy. However, the MAT record of the Store Bælt section did not reveal this warming.

Organic geochemistry of Cretaceous black shales

Organic-carbon-rich 'black shales' and adjacent organic-carbon-poor rocks from three different Cretaceous settings encountered during ODP Leg 103 have been studied by organic geochemical methods. Rock-Eval analysis, carbon isotope data, and lipid biomarkers show organic matter to contain varying proportions of marine and continental materials. In Hauterivian-Barremian organic-carbon-rich marlstone turbidites, large amounts of land-derived organic matter are found. Aptian-Albian black-colored shales are interspersed within green claystones, from which they differ by containing more marine organic matter. An abbreviated layer of black shale from the Cenomanian/Turonian boundary is dominated by well-preserved marine organic matter. Downslope transport and rapid reburial within a predominantly oxygenated deep-water setting created most of these examples of black shales, except for the Cenomanian-Turonian deposits in which deep-water anoxia may have been involved.