Distribution of trace fossils and ichnofabric indices in ODP holes of Leg 119

Trace fossils and ichnofabric were examined from cores of Late Cretaceous to Quaternary age recovered from the Kerguelen Plateau, Indian Ocean. Nearly all of the strata are completely bioturbated, with ichnofabric index 6 most commonly recorded. Preserved discrete trace fossils include Chondrites, Planolites, Zoophycos, and Thalassinoides. A continuous Cretaceous/Tertiary boundary section preserved at ODP Site 738 occurs within a 15-cm-thick interval of laminated sediments. The lack of bioturbation indicates the disappearance of bioturbating organisms from the seafloor, possibly as a result of the same factors that caused the mass extinction or changes in other environmental conditions - most probably, bottom-water oxygen concentrations.

Vertical distribution of large particulate matter in the Western Mediterranean Sea

The relationship between mesoscale hydrodynamics and the distribution of large particulate matter (LPM, particles larger than 200 ?m) in the first 1000 m of the Western Mediterranean basin was studied with a microprocessor-driven CTD-video package, the Underwater Video Profiler (UVP). Observations made during the last decade showed that, in late spring and summer, LPM concentration was high in the coastal part of the Western Mediterranean basin at the shelf break and near the continental slope (computed maximum: 149 ?g C/l between 0 and 100 m near the Spanish coast of the Gibraltar Strait). LPM concentration decreased further offshore into the central Mediterranean Sea where, below 100 m, it remained uniformly low, ranging from 2 to 4 ?g C/l. However, a strong variability was observed in the different mesoscale structures such as the Almeria-Oran jet in the Alboran Sea or the Algerian eddies. LPM concentration was up to one order of magnitude higher in fronts and eddies than in the adjacent oligotrophic Mediterranean waters (i.e. 35 vs. 8 ?g C/l in the Alboran Sea or 16 vs. 3 ?g C/l in a small shear cyclonic eddy). Our observations suggest that LPM spatial heterogeneity generated by the upper layer mesoscale hydrodynamics extends into deeper layers. Consequently, the superficial mesoscale dynamics may significantly contribute to the biogeochemical cycling between the upper and meso-pelagic layers.

Aragonite distribution and preservation of sediment cores from the Brazilian Continental Slope

We present late Quaternary records of aragonite preservation determined for sediment cores recovered on the Brazilian Continental Slope (1790-2585 m water depth) where North Atlantic Deep Water (NADW) dominates at present. We have used various indirect dissolution proxies (carbonate content, aragonite/calcite contents, and sand percentages) as well as gastropodal abundances and fragmentation of Limacina inflata to determine the state of aragonite preservation. In addition, microscopic investigations of the dissolution susceptibility of three Limacina species yielded the Limacina Dissolution Index which correlates well with most of the other proxies. Excellent preservation of aragonite was found in the Holocene section, whereas aragonite dissolution gradually increases downcore. This general pattern is attributed to an overall increase in aragonite corrosiveness of pore waters. Overprinted on this early diagenetic trend are high-frequency fluctuations of aragonite preservation, which may be related to climatically induced variations of intermediate water masses.