(Table 1) Lithological and organic-geochemical compositions of bottom sediments from the Southwestern Indian Ocean (Mozambique Basin)

Geochemical changes in organic matter of bottom sediments from the Mozambique Basin at the river-sea barrier from the mouths of the Zambezi and Limpopo rivers toward the pelagic zone are discussed. Changes in bitumen, hydrolyzable material, humic acids, amino acids, n-alkanes, and polycyclic aromatic compounds resulting from genetic and diagenetic factors are described. This information is significant for paleoceanology reconstructions and for knowing ways of organic matter transformation into fossil forms.

Water temperature, salinity, DOC content and THNS concentration in samples taken during POLARSTERN cruise to the Fram Strait and Greenland Sea

Dissolved organic matter (DOM) was isolated with XAD-2 and 4 resins from different water masses of the Greenland Sea and Fram Strait. The contribution of XAD-extractable dissolved organic carbon (DOC), operationally defined as 'recalcitrant' or humic substances, to total DOC was in the range of 45 ± 9% in surface waters and 60 ± 6% in deep waters. The carbohydrate concentration and composition were determined using the l-tryptophan/sulfuric acid method (for the bulk carbohydrate concentration, TCHO) and high performance anion-exchange chromatography after sulfuric acid hydrolysis (for the distribution of total hydrolysable neutral sugars, THNS). Carbohydrates contributed up to 6.8% to both total and recalcitrant DOC. TCHO contribution to total DOC decreased with depth from on average 4.1 ± 1.2% in surface waters to 2.2 ± 1.0% in deep waters, whereas the THNS contribution was similar in both layers, accounting for 2.5 ± 1.6% (surface) and 2.4 ± 0.2% (at depth). TCHO contribution to XAD-extractable DOC also decreased with depth from 4.5 ± 1.7% to 2.1 ± 1.0%, whereas THNS contribution was almost constant, with yields of 0.5 ± 0.3% for surface samples and 0.6 ± 0.1% at depth. The molecular size distribution of the recalcitrant DOM showed for all fractions a clear trend towards small molecules in the deep sea. More than half of the XAD-extractable carbohydrates of surface samples and more than 70% of deep sea samples were found in the nonpolar fraction from XAD, which was eluted with methanol. Glucose was the dominant carbohydrate in the surface water samples, whereas in the deep sea the composition was more uniform. In the XAD extracts, the compositions were less variable than in the original samples. The neutral sugar composition, in particular glucose and the deoxysugars, is indicative of the diagenetic state of the extracted DOM. The molar ratio (fucose + rhamnose)/(arabinose + xylose) was lowest for deep sea extractable DOM, indicating a high contribution of material modified by microorganisms. The THNS composition and distribution reveal that "recalcitrant" carbohydrates are heteropolysaccharides, carbohydrate units incorporated into a framework of a highly nonpolar structure with a lack of functional groups.

(Table T1) Kerogen and organic constituents in ODP Hole 183-1138A, Kerguelen Plateau

Mid-Cretaceous sediments recovered during Ocean Drilling Program Leg 183 (Cores 183-1138A-69R to 73R) on the central Kerguelen Plateau have been analyzed palynologically and paleobotanically to determine the age of the strata and to reconstruct vegetational development and paleoecology. The lower strata (Cores 183-1138A-71R to 73R), a dark, organic-rich silty claystone with many wood fragments and fern remains (sedimentary Unit VI), certainly of terrestrial origin, directly overlies the volcanic basement, which is dated as latest Albian (~95 to 103 Ma) to earliest Cenomanian. The age of the terrestrial strata can be determined by sporomorphs as late Albian to earliest Cenomanian as well. This shows that parts of the central Kerguelen Plateau must have been subaerial at least until the late Albian and were covered with a diverse high-latitude flora, probably dense conifer forest with various fern taxa in the undergrowth. Early angiosperms are also present. The vegetational character represented in Unit VI did not change significantly through time. However, varying percentages of several sporomorph groups seem to show recurring abundance variations, which might possibly be cyclic, caused by Milankovitch-type cyclic events. Cores 183-1138A-67R through 69R, of open marine origin, contain medium- to high-diversity dinocyst assemblages. Based on previous stratigraphic zonation schemes, the ages of these strata range within the Heterosphaeridium Superzone, from the Palaeohystrichophora infusorioides Zone to the Conosphaeridium striatoconus Zone, which correlates to the latest Cenomanian to Coniacian.