(Tables 1-3) Silicon dioxide, Corg and trace element concentrations in sediments of the outer Eckernfoerder Bay, Western Baltic Sea

The main question, posed in the work scheme before laboratory analysis was started, was expressed as follows: Do marked seasonal fluctuations occur in trace element content of the sediment surface, and what are the probable influences of factors such as changing hydrographical parameters, plankton sequence etc. ? Special attention was paid to elements known as pollutants, for example mercury. Within this framework samples have been analysed for their contents of manganese, iron, zinc, lead, and mercury. The amounts of silica and organically-bound carbon serve in most cases as reference values for the trace element content. On sand temporary conditions of increased C org content raise the concentrations of all determined elements. Especially the values reached for mercury in July are worth nothing. It is concluded that Zn, Pb, and Hg tend to enrich with respect to C org as the decomposition of organic matter progresses. On mud-sand flocculation and precipitation of Mn/Fe-hydroxides probably represent an additional concentrating factor for the other elements as the relationship of the results for zinc and manganese shows. Manganese may indicate a seasonally related concentrating cycle at the sediment surface.

Composition of sedimentary rocks from the Burun-Tas Formation, Bol'shoi Lyakhov Island (New Siberian Islands)

Graywackes and shales of the Bol'shoi Lyakhov Island originally attributed to Mesozoic were subsequently considered based on microfossils as Late Proterozoic in age. At present, these sediments in the greater part of the island are dated back to Permian based on palynological assemblages. In the examined area of the island, this siliciclastic complex is intensely deformed and tectonically juxtaposed with blocks of oceanic and island-arc rocks exhumed along the South Anyui suture. The complex is largely composed of turbidites with members displaying hummocky cross-stratification. Studied mineral and geochemical charac¬teristics of the rocks defined three provenances of clastic material: volcanic island arc, sedimentary cover and/or basement of an ancient platform, and exotic blocks of oceanic and island-arc rocks such as serpentinites and amphibolites. All rock associations represent elements of an orogenic structure that originated by collision of the New Siberian continental block with the Anyui-Svyatoi Nos island arc. Flyschoid sediments accumu¬lated in a foredeep in front of the latter structure in the course of collision. Late Jurassic volcanics belonging to the Anyui-Svyatoi Nos island arc determine the lower age limit of syncollision siliciclastic rocks. Presence of Late Jurassic zircons in sandstones of the flyschoid sequence in the Bol'shoi Lyakhov Island is confirmed by fission-track dating. The upper age limit is determined by Aptian-Albian postcollision granites and diorites intruding the siliciclastic complex. Consequently, the flyschoid sequence is within stratigraphic range from the terminal Late Jurassic to Neocomian. It appears that Permian age of sediments suggested earlier is based on redeposited organic remains. The same Late Jurassic-Neocomian age and lithology are characteristic of fossiliferous siliciclastic sequences of the Stolbovoi and Malyi Lyakhov islands, the New Siberian Archipelago, and of graywackes in the South Anyui area in the Chukchi Peninsula. All these sediments accumulated in a spacious foredeep that formed in the course the late Cimmerian orogeny along the southern margin of the Arctic conti¬nental block.

Diatom oxygen and silicon isotopes data from IODP Hole 323-U1341B in the Bering Sea through the late Pliocene and over the onset of major Northern Hemisphere Glaciation

The Bering Sea is one of the most biologically productive regions in the marine system and plays a key role in regulating the flow of waters to the Arctic Ocean and into the subarctic North Pacific Ocean. Cores from Integrated Ocean Drilling Program (IODP) Expedition 323 to the Bering Sea provide the first opportunity to obtain reconstructions from the region that extend back to the Pliocene. Previous research at Bowers Ridge, south Bering Sea, has revealed stable levels of siliceous productivity over the onset of major Northern Hemisphere Glaciation (NHG) (circa 2.85-2.73 Ma). However, diatom silica isotope records of oxygen (d18Odiatom) and silicon (d30Sidiatom) presented here demonstrate that this interval was associated with a progressive increase in the supply of silicic acid to the region, superimposed on shift to a more dynamic environment characterized by colder temperatures and increased sea ice. This concluded at 2.58 Ma with a sharp increase in diatom productivity, further increases in photic zone nutrient availability and a permanent shift to colder sea surface conditions. These transitions are suggested to reflect a gradually more intense nutrient leakage from the subarctic northwest Pacific Ocean, with increases in productivity further aided by increased sea ice- and wind-driven mixing in the Bering Sea. In suggesting a linkage in biogeochemical cycling between the south Bering Sea and subarctic Northwest Pacific Ocean, mainly via the Kamchatka Strait, this work highlights the need to consider the interconnectivity of these two systems when future reconstructions are carried out in the region.