(Table 1) Vertical fluxes of sediment matter and organic carbon in the Kara Sea and in the Yenisey and Ob estuaries

Sedimentary particle fluxes in the Kara Sea and in the Ob and Yenisey estuaries were first estimated and particulate matter composition was studied in September 1993 during Cruise 49 of R/V Dmitry Mendeleev. Twenty three bottom stations with sediment traps were deployed, and samples were collected from 13 stations. Particle fluxes ranged from 9.0 to 62.6 mg/m**2/day to the north of the Ob and Yenisey estuaries and were 18.7 to 62.0 mg/m**2/day in the southwestern part of the Kara Sea. Fluxes were up to 1321 mg/m**2/day in the Ob estuary and up to 22156 mg/m**2/day in the Yenisey estuary. Organic matter fluxes were estimated as 0.71-3.29, 4.28-9.04, 26.7, and 368 mg/m**2/day, respectively. Particulate matter is largely represented by pellets of planktic Crustacea and by "sea snow" flakes mainly composed of diatoms. Rapidly settling particles are extensively inhabited by bacterial flora.

Speciation of metals in bottom sediments from the south Kara Sea and Ob and Yenisei estuarine zones

Speciation of Fe, Mn, Zn, Cu, Co, Ni, Cr, Pb, and Cd was studied in 52 samples of bottom sediments collected during Cruise 49 of the R/V "Dmitry Mendeleev" to the estuaries of the Ob and Yenisei rivers and to the southwest Kara Sea. Immediately after sampling the samples were subjected to on-board consecutive extraction to separate metal species according to their modes of occurrence in the sediments: (1) adsorbed, (2) amorphous Fe-Mn hydroxides and related metals, (3) organic + sulfide, and (4) residual, or lithogenic. Atomic absorption spectroscopy of the extracts was carried out at a stationary laboratory. Distribution of Fe, Zn, Cu, Co, Ni, Cr, Pb, and Cd species is characterized by predominance of lithogenic or geochemically inert modes (70-95% of bulk contents), in which the metals are bound in terrigenous and clastic mineral particles and organic detritus. About half of total Mn amount and 15-30% of Zn and Cu are contained in geochemically mobile modes. Spatiotemporal variations in proportions of the metal species in the surface layer of sediments along sub-meridional sections and through vertical sections of bottom sediment cores testify that Mn and, to a lesser extent, Cu are the most sensitive to changes in sedimentation environment. The role of their geochemically mobile species notably increases under reducing conditions.

Ages and two-way travel times of ODP Sites 180-1109, 180-1115 and 180-1118

Synthetic seismograms are constructed from check shot-corrected velocity and density measurements collected during Ocean Drilling Program (ODP) Leg 180 at Sites 1109, 1115, and 1118. The synthetic seismograms facilitate direct correlation of a coincident multichannel seismic (MCS) profile with borehole data collected at the three sites. The MCS data and the synthetic seismograms correlate very well, with most major reflectors successfully reproduced in the synthetics. Our results enable a direct calibration of the MCS data in terms of age, paleoenvironment, and subsidence history. Seismic reflectors are time correlative within stratigraphic resolution but are often observed to result from different lithologies across strike. Our results facilitate the extrapolation of the sedimentation history into an unsampled section of Site 1118 and enable a full correlation between the three sites using all the data collected during ODP Leg 180. This study forms the foundation for regionalizing the site data to the northern margin of the Woodlark Basin, where the transition from continental rifting to seafloor spreading is taking place.