Pyrolyzable carbon, temperature maximum, production index and lithology for DSDP Leg 96 holes

Sediments from Deep Sea Drilling Project Sites 615, 617, 618, 619, and 620-623 were subjected to pyrolysis. The sediments are immature with respect to petroleum generation as determined by production index values of less than 0.1 and Tmax values of 460-480°C. The amount of pyrolyzable organic matter was moderately low as compared to typical petroleum source rocks. The immature organic matter present does not appear to contain a significant proportion of woody material as shown by the low gas-generating potential. Typical overbank sediments from Sites 617 and 620 generally show higher P2 values (500-800 µg hydrocarbon per g dry weight sediment) than typical channel-fill sediments from Sites 621 and 622 (P2 = 450-560 µg/g). Tmax for both types of sediment remained very constant (462-468 °C) with a slight elevation (+ 15°C) occurring in samples containing lignite. The highest P2 values occurred in sections described as turbidites. Very low P2 values (about 50 µg/g) occurred in sands. P2 values for shallower sections of basin Sites 618 and 619 tended to be higher (900-1000 µg/g) and decreased in deeper, more terrigenous sections of Site 619. Preliminary experiments indicate that microbiological degradation of sediment organic matter causes a decrease in P2. Pyrolyzable organic matter from lower fan Site 623 appears to increase with depth in two different sediment sequences (40-85 and 95-125 m sub-bottom). Organic matter type, as shown by pyrolysis capillary gas chromatography (GC) patterns, was generally the same throughout the well, with much more scatter occurring in the deepest sections (130-155 m sub-bottom). One major and two minor organic matter types could be recognized in both fan and basin sites drilled on Leg 96.

Distribution of late Quaternary calcareous nannofossils in DSDP Leg 96 sites

Sediments from holes drilled at 11 sites in the northern Gulf of Mexico during Deep Sea Drilling Project Leg 96 were analyzed for calcareous nannofossil content. All sediments recovered are Holocene and late Pleistocene in age and are within the Emiliania huxleyi Zone. The datum level represented by the lowest stratigraphic occurrence of dominant E. huxleyi occurs at two sites (Sites 615 and 619) and can be dated at approximately 84,000 yr. ago at Site 619. Reworked Cretaceous nannofossils are generally common or abundant and dominate the floral assemblages of the late Wisconsin glacial sediments. When present, indigenous late Quaternary species are rare or few in abundance. Slight increases in the contemporaneous Quaternary component of the floral assemblages can be documented by the use of a calculated in s/fu/reworked ratio. This ratio, based on the relative abundances of the indigenous Quaternary taxa and reworked taxa, shows potential both for local correlations between drill sites and for correlation with glacio-eustatic fluctuations during the late Pleistocene.

Turbidity measurements in 96-wells microplates to determine the densities of copiotrophic and oligotrophic bacteria with the Most-Probable-Number-method during POLARSTERN cruise ANT-XI/2

A new microtiter-plate dilution method was applied during the expedition ANTARKTIS-XI/2 with RV Polarstern to determine the distribution of copiotrophic and oligotrophic bacteria in the water columns at polar fronts. Twofold serial dilutions were performed with an eight-channel Electrapette in 96-wells plates by mixing 150 µl of seawater with 150 µl of copiotrophic or olitrophic Trypticase-Broth, three times per well. After incubation of about 6 month at 2 °C, turbidities were measured with an eight-channel photometer at 405 nm and combinations of positive test results for three consecutive dilutions chosen and compared with a Most Probable Number table, calculated for 8 replicates and twofold serial dilutions. Densities of 12 to 661 cells/ml for copiotrophs, and 1 to 39 cells/ml for oligotrophs were found. Colony Forming Units on copiotrophic Trypticase-Agar were between 6 and 847 cells/ml, which is in the same range as determined with the MPN method.