(Table 1) Carbon and isotopic composition of organic carbon in sediments from DSDP Leg 56 Holes

We have analyzed inorganic and organic carbons and determined the isotopic composition of both sedimentary organic carbon and inorganic carbon in carbonates contained in sediments recovered from Holes 434, 434A, 434B, 435, and 435A in the landward slope of Japan and from Hole 436 in the oceanic slope of the Japan Trench. Both inorganic and organic carbons were assayed at the P. P. Shirshov Institute of Oceanology, in the same sample, using the Knopp technique and measuring evolved CO2 gravimetrically. Each sample was analyzed twice in parallel. Measurements were of a ±0.05 per cent accuracy and a probability level of 0.95. Carbon isotopic analysis was carried out on a MI-1305 mass spectrometer at the I. M. Gubkin Institute of Petrochemical and Gas Industry and the results presented as dC13 values related to the PDB standard. The procedure for preparing samples for organic carbon isotopic analysis involved (1) drying damp sediments at 60°C; (2) treating samples, while heating, with 10 N HCl to remove carbonate carbon; and (3) evaporating surplus HCl at 60°C. The organic substance was turned to CO2 by oxidizing it in an oxygen atmosphere. To prepare samples for inorganic carbon isotopic analysis we decomposed the carbonates with orthophosphoric acid and refined the gas evolved. The dC13 measurements, including a full cycle of sample preparation, were of a ±0.5 per cent accuracy and a probability level of 0.95.

Calcium carbonate and organic carbon content, and stable isotope composition of sediment core Y71-3-2

Planktic stable isotopes by Mix for this paper and Pisias and Mix (1997)

(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.

(Table 1) Composition of organic matter in bottom sediments from the Kuril-Kamchatka Trench

From results of analyses of sediment samples collected on a profile crossing the Kuril-Kamchatka Trench distribution of organic D, N. carbohydrates, lipids and humic substances was established, as well as nature of their relationship with amorphous silica and clay fraction. Sum of the main biochemical groups of organic matter in the surface layer of sediments (0-1 cm) from the Kuril-Kamchatka Trench amounts to about 15%; neogenetic forms not encountered in living organisms make up 85% of organic matter. Among such forms 26% comprise humic substances formed during initial stages of polymerization of decomposition products of biochemical macromolecules.