Age determination of sediments of Site LO09-14 (Table 1)

A composite record (LO09-14) of three sediment cores from the subpolar North Atlantic (Reykjanes Ridge) was investigated in order to assess surface ocean variability during the last 11 kyr. The core site is today partly under the influence of the Irminger Current (IC), a branch of the North Atlantic Drift continuing northwestward around Iceland. However, it is also proximal to the Sub-Arctic Front (SAF) that may cause extra dynamic hydrographic conditions. We used statistical methods applied to the fossil assemblages of diatoms to reconstruct quantitative sea surface temperatures (SSTs). Our investigations give evidence for different regional signatures of Holocene surface oceanographic changes in the North Atlantic. Core LO09-14 reveal relatively low and highly variable SSTs during the early Holocene, indicating a weak IC and increased advection of subpolar water over the site. A mid-Holocene thermal optimum with a strong IC occurs from 7.5 to 5 kyr and is followed by cooler and more stable late Holocene surface conditions. Several intervals throughout the Holocene are dominated by the diatom species Rhizosolenia borealis, which we suggest indicates proximity to a strongly defined convergence front, most likely the SAF. Several coolings, reflecting southeastward advection of cold and ice-bearing waters, occur at 10.4, 9.8, 8.3, 7.9, 6.4, 4.7, 4.3 and 2.8 kyr. The cooling events recorded in the LO09-14 SSTs correlate well with both other surface records from the area and the NADW reductions observed at ODP Site 980 indicating a surface-deepwater linkage through the Holocene.

(Table 1) Petrological description and consolidation properties of ODP Site 186-1150 and Hole 186-1151A

In order to determine the shear parameters of the forearc sedimentary strata drilled during Ocean Drilling Program Leg 186, West Pacific Seismic Network, Japan Trench, eight whole-round samples were selected from different depths in the drilled sections of Sites 1150 and 1151. Whereas Site 1150 lays above the seismically active part of the subduction zone, Site 1151 is situated in an aseismic zone. The aim of the triaxial tests was, apart from determination of the static stress strain behavior of the sediments, to test the hypothesis that the static stress strain parameter could differ for each sites. In order to simulate undrained deformation conditions according to the high clay mineral content of the strata, consolidated undrained shear tests were performed in a triaxial testing setup. Measurements of water content, grain density, organic content, and microtextural investigations under the scanning electron microscope (SEM) accompanied the compression experiments. After the saturation and consolidation stages were completed, failure occurred in the compression stage of the experiments at peak strengths of 280-7278 kPa. The stiffness moduli calculated for each sample from differential stress vs. strain curves show a linear relationship with depth and range between 181 and 5827 kPa. Under the SEM, the artificial fault planes of the tested specimen only show partial alignment of clay minerals because of the high content of microfossils.

(Table 1) Porosity, particle diameter, ATP content and carbon and nitrogen composition of ODP Site 164-994 sediments

Sediment samples were obtained for detailed Adenosine 5'-Triphosphate (ATP) analysis down to 57.8 m below the seafloor (mbsf). The samples were also analyzed for particle-size distribution, calcium carbonate (CaCO3), organic carbon, and total nitrogen. The concentrations of ATP ranged between 360 and 7050 pg/g (dry weight sediment), which agree well with a limited number of direct bacteria counts. Principal component analyses show that 63% of the total variance can be accounted for by the first two principal components. The concentration of ATP (bacterial numbers by inference) is virtually independent of the concentration of sedimentary organic carbon, but correlates with CaCO3 and coarse particles.