(Tables 1, 3) Component composition of organic particles in samples from ODP Site 131-808

Analysis of the palynofacies and miospore thermal alteration indices (TAI) of sediments from ODP Site 808 in the Nankai Trough was undertaken to determine (1) the source, depositional environment, and diagenesis of organic matter in the accreted sediments, and (2) the thermal structure and history of the prism and its relationship to fluid flow. Using the Hartax classification system, two palynofacies were recognized in the sedimentary sequence. Facies 1 occurs within the upper 600 m of trench-wedge turbidites (sedimentation rate > 1 km/m.y.) and contains >50% inertite particles. The rest of the assemblage is dominated by well-preserved phytoclasts and contains small amounts of poorly preserved phytoclasts and well-preserved scleratoclasts. Facies 2 occurs within the Shikoku Basin hemipelagites (600-1300 m below seafloor; sedimentation rate <150 m/m.y.) and contains over two-thirds inertite particles. The rest of the assemblage is dominated by poorly preserved phytoclasts. Miospores and marine phytoplankton compose only a small percentage of both palynofacies. Degraded organic matter is most noticeable in Facies 2, whereas its presence in Facies 1 is overshadowed by the high influx of well-preserved primary organic matter. Most of the degraded organic matter and inertite is interpreted to be reworked. Some of the degraded organic matter may be primary, and may have experienced more biodegradation and thermal alteration in Facies 2 than in Facies 1. TAI values indicate an immature stage of organic maturation (< 2) down to about 900 mbsf. Below this, samples show an increase with depth to a mature stage, reaching peak levels of about 3 just above basement. Samples from within the thrust fault and decollement zones do not show levels of maturity significantly greater than those of surrounding samples, leaving uncertain whether hot fluids have migrated along these fault boundaries in the past.

(Tables 1-3) Amphipod species observed under Antarctic pack ice during POLARSTERN cruises ANT-XXI/4, ANT-XXII/2 and ANT-XXIII/6

During three Antarctic expeditions (2004, ANT XXI-4 and XXII-2; 2006, ANT XXIII-6) with the German research icebreaker R/V Polarstern, six different amphipod species were recorded under the pack ice of the Weddell Sea and the Lazarev Sea. These cruises covered Austral autumn (April), summer (December) and winter (August) situations, respectively. Five of the amphipod species recorded here belong to the family Eusiridae (Eusirus antarcticus, E. laticarpus, E. microps, E. perdentatus and E. tridentatus), while the last belongs to the Lysianassidea, genus Cheirimedon (cf. femoratus). Sampling was performed by a specially designed under-ice trawl in the Lazarev Sea, whereas in the Weddell Sea sampling was done by scuba divers and deployment of baited traps. In the Weddell Sea, individuals of E. antarcticus and E. tridentatus were repeatedly observed in situ during under-ice dives, and single individuals were even found in the infiltration layer. Also in aquarium observations, individuals of E. antarcticus and E. tridentatus attached themselves readily to sea ice. Feeding experiments on E. antarcticus and E. tridentatus indicated a carnivorous diet. Individuals of the Lysianassoid Cheirimedon were only collected in baited traps there. Repeated conventional zooplankton hauls performed in parallel to this study did not record any of these amphipods from the water column. In the Lazarev Sea, E. microps, E. perdentatus and E. laticarpus were regularly found in under-ice trawls. We discuss the origin and possible sympagic life style of these amphipods.

Description of recent sediments of Nile Delta, Red Sea and Gulf of Aden (Table 1-3)

The study of textural, structural, chemical, and physical properties of fine-grained recent marine sediments leads to the conclusion that only a few compositional factors are responsible for significant changes in mass physical characteristics in the upper meters below sea bottom. Fossil-induced porosity increases water content and liquid limit. It also seems to have partially influenced the plastic limit and plasticity index of calcareous sandy silts from the Red Sea and the western Gulf of Aden so that they become similar to the montmorillonite rich prodelta clays from the Nile Delta. Diagrams based on liquid limit and plasticity loose their original meaning in these cases. Activity of sediments rich in microorganisms can be higher than that of montmorillonitic clay. The shear strength-depth relationship of normally consolidated sediments is surprisingly little influenced by changes in sand or clay content and clay mineralogy. Only high lime content, submarine erosion and beginning cementation increase the strength considerably. Erosional disconformities near the present surface can be deduced from the strength-depth curve when as little as 1 or 2 m sediment have been removed. Flat or irregular strength-depth curves indicate beginning cementation and probably discontinuous sedimentation, provided the composition of the material remains in some degree constant. In our samples diagenetic pyrite, but no recristallisation of carbonates could be detected under the microscope. Underconsolidation and excess pore-water pressure, factors which tend to foster submarine slides, mud lumps, and diapiric folding, seem to be restricted Varito areas with mainly rapidly deposited, homogeneous or layered sediments. But where an abundance of burrowing organisms increases the vertical permeability of the sediment, normal consolidation and stable deposits are to be expected, at least in the upper meters below the present surface. According to 14C-determinations on calcareous microorganisms the rate of deposition of the investigated sediments seems to range from 26 to 167 cm per 1000 years.