Description: Three long sediment cores from the Makarov Basin have been subjected to detailed paleomagnetic and rock magnetic analyses. Investigated sediments are dominated by normal polarity including short reversal excursions, indicating that most of the sediments are of Brunhes age. In general, the recovered sediments show only low to moderate variability in concentration and grain size of the remanence-carrying minerals. Estimations of relative paleointensity variations yielded a well-documented succession of pronounced lows and highs that could be correlated to published reference curves. However, together with five accelerator mass spectrometry C-14 ages and an incomplete Be-10 record, still two different interpretations of the paleomagnetic data are possible, with long-term sedimentation rates of either 1.3 or 4 cm kyr(-1) However, both models implicate highly variable sedimentation rates of up to 10 cm kyr(-1), and abrupt changes in rock magnetic parameters might even indicate several hiatuses.

Description: High-resolution seismic profiles (PARASOUND, 4 kHz) of the western Laptev Sea continental margin and the adjacent Vilkitsky Strait were studied in order to gain new evidence about the Weichselian glaciations in Central Siberia and to test reconstructions of maximum ice sheet extents. Four regionally correlatable seismic units, named I (youngest) to IV, were identified in the upper Quaternary sedimentary succession: (I) a thin drape; (II) prograding wedge-shaped deposits along the shelf edge; (III) layered sediments of draping and infilling character with increasing thickness towards the western Laptev Sea shelf edge and the Vilkitsky Strait; (IV) stacked debris-flow deposits. The thin drape of unit I is radiocarbon-dated to Holocene and mainly deposited during the transgression of the Laptev Sea. The wedge-shaped deposits of unit II are interpreted as river deltas, referring to point sources along the shelf edge during the Late Weichselian sea-level lowstand. This indicates that the river input across the Laptev Sea shelf was continuous during marine isotope stage (MIS) 2. The layered sediments of unit III suggest hemipelagic conditions indicative of a sea-level highstand. The pronounced thickening of unit III towards the shelf edge of the western Laptev Sea reflects the lowering of the global sea level during MIS 3. This is associated with increased riverine input due to the northward shift of the Siberian coastline. The stacked debris-flow deposits of unit IV extend continuously from the shelf edge in the Vilkitsky Strait to the continental rise of the western Laptev Sea continental margin. They indicate that large quantities of sediments were deposited directly on the upper continental slope during advances of the Kara Sea ice sheet to the shelf break. These ice-proximal conditions are presumably linked to the Middle Weichselian glaciation (MIS 4). Our evidence confirm earlier reconstructions, suggesting that in central Siberia, the Middle Weichselian glaciation (MIS 4) was of larger extent than the Late Weichselian glaciation (MIS 2).

Description: During the expeditions ARK IX/4 (1993) and ARK XI/1 (1995) by RV "Polarstern" glaciomarine deposits were discovered east off Severnaya Zemlya, in the Vilkitsky Strait and Vilkitsky-Khatanga Channel using PARASOUND subbottom profiling. For reconstruction of the palaeoenvironment and glacial history of the Severnaya Zemlya archipelago the geophysical properties (magnetic susceptibility, wet bulk density, pwave velocity, porosity and water content) of gravity cores taken in this area were studied using a high resolution multi-sensor core logger (MSCL). Additional investigations included the determination of fine lithological structures and ice rafted debris (IRD) by x-ray photographs, grain-size (sand, silt, clay), grain-size distribution of silt, and clay mineral distribution by x-ray diffraction of four sediment cores in key positions. The comparison of the results with PARASOUND-profiles and AMS 14C datings allowed the identification of 5 seismic units and their stratigraphical correlation from the Vilkitsky-Khatanga Channel into the Vilkitsky Strait.The results can be summarized as follows:Morainic ridges were identified along the north eastern continental slope of Severnaya Zemlya and in the Vilkitsky Strait (seismic unit 5). They were produced by a former glaciation of the archipelago of unkown age. Large debris flow deposits (seismic unit 4) in the Vilkitsky Strait indicating ice-proximal conditions are presumably linked to the glaciation of Severnaya Zemlya and the Taymyr Peninsula during marine isotope stage 4. In the Vilkitsky Strait and Vilkitsky-Khatanga Channel, clayey sediments (seismic unit 3) reflect hemipelagic accumulation under a possibly frequently closed sea-ice cover showing no evidence of ice-proximal conditions at stage 3. Stage 2 is characterized by a global sea-Ievel lowering of approximately 120 m resulting in the formation of a sediment fan (seismic unit 2) belonging to the river Khatanga at the shelf break of the Laptev Sea close to the Vilkitsky-Khatanga Channel and possible fjord-like conditions in the Vilkitsky Strait. The appearance of a diamicton in the Schokalsky Channel suggests, that presumably during stage 2 the Schokalsky Strait was closed by a grounded ice-shield. Massive meltwater sediments occurring in the western Vilkitsky Strait could be related to an existing ice-shield in the Kara Sea during stage 2. An increased input of smectite and magnetite by the Khatanga during termination 1 a could be interpreted as deglaciation of the Putoran-Plateau which was ice-covered at stage 2. The asymmetrie accumulation of Holocene Sediments (seismic unit 1) in the Vilkitsky Strait and Vilkitsky-Khatanga Channel may have depended on the formation of dense and cold water bottom currents caused by sea-ice production on the Kara shelf. The local appearance of the Holocene at the continental slope of Severnaya Zemlya could have been produced by conturites.

Description: This paper is devoted to studies of clay minerals from two cores collected in the northern and central regions of the St. Anna Trough, the largest trough of the Kara Sea. Upper Quaternary glacial, glaciomarine, and marine deposits are characterized by various contents of kaolinite, chlorite, illite, and smectite. It is established that, from older to younger deposits, amounts of kaolinite and chlorite generally decrease, while those of illite and smectite, on the contrary, increase. A joint analysis of distributions of clay and heavy minerals over the section allowed us to refine position of sources for terrigenous matter and their temporal variability. It is shown changes in sources of supply were directly related to climate changes that occurred when passing from glacial to marine sedimentation environments.

Description: During summer periods of 2003-2005, spatial and vertical distributions of suspended particulate matter and bacteria in stratified and homogeneous waters of the White Sea was studied. Results of the study of various quantitative characteristics of the suspended particulate matter (first of all, area of surface and volumetric and mass concentrations) and abundance of microorganisms in water are discussed. A direct correlation between the value of the surface area of the suspended particulate matter and the total number of bacteria in water is revealed. However, it was manifested only during the early summer period of observations and was not expressed at the end of summer. Enhanced surface area of the suspended particulate matter can indicate the higher biochemical activity of its particles. Influence of pelitic (〈0.01 mm) size fraction on bacteria abundance in different parts of the sea during summer is estimated.