Tab. 1: Ar40/Ar39 results from Kuyul terrane, northeastern Russia

The Kamchatka Peninsula of northeastern Russia is located along the northwestern margin of the Bering Sea and consists of zones of complexly deformed accreted terranes. Along the northern portion of the peninsula, progressing from then orthwestem Bering Sea inland the Olyutorskiy, Ukelayat, and Koryak superterranes area acreted to the Okhotsk-Chukotsk volcanic-plutonic bell in northern-most Kamchatka. A sedimentary sequence of Albian to Maastrichtian age overlap terranes and units of the Koryak superterrane and constrains their accretion time with this region of the North America plate. Ophiolite complexes, widespread within the Koryak superterrane, are associated with serpentinite melanges and some of the ophiolite terranes include large portions of weakly serpentinized hyperbasites, layered gabbro, sheeted dikes, and pillow basalts outcropping as internally coherent blocks within a sheared melange matrix. Interpretation of magnetic anomalies allow the correlation of the Ukelayat with the West Kamchatka and Sredinny Range superterranes. The Olyutorskiy composite terrane may be correlated with the central and southern Kamchatka Peninsula Litke, Eastern Ranges and Vetlov composite terranes. The most "out-board" of the central and southern Kamchatka Peninsula terranes is the Kronotsky composite terrane, weil exposed along the Kamchatka, Kronotsky and Shipunsky Capes. Using regional geological constraints, paleomagnetism, and plate kinematic models for the Pacific basin a regional model can be proposed in which accretion of the Koryak composite terrane to the North America plate occurs during the Campanian-Maastrichtian, followed by the accretion of the Olyutorskiy composite terrane in the Middle Eocene, and the Late Oligocene-Early Miocene collision of the Kronotsky composite terrane. A revised age estimate of a key overlapping sedirnentary sequence of the Koryak superterrane, calibrated with new Ar40/Ar39 data, supports its Late Cretaceous accretion age.

Heat flow values in the Sea of Okhotsk region

Tectonic structure and anomalous distributions of geophysical fields of the Sea of Okhotsk region are considered; the lack of reliable data on age of the lithosphere beneath basins of various origin in the Sea of Okhotsk is noted. Model calculations based on geological and geophysical data yielded 65 Ma (Cretaceous-Paleocene boundary) age for the Central Okhotsk rise underlain by the continental lithosphere. This estimate agrees with the age (the end of Cretaceous) derived from seismostratigraphic data. A comparative analysis of theoretical and measured heat flows in the Akademii Nauk Rise, underlain by the thinned continental crust, is performed. The analysis points to a higher (by 20%) value of the measured thermal background of the rise, which is consistent with high negative gradient of gravity anomalies in this area. Calculations yielded 36 Ma (Early Oligocene) age and lithosphere thickness of 50 km for the South Okhotsk depression, whose seafloor was formed by processes of back-arc spreading. The estimated age of the depression is supported by kinematic data on the region; the calculated thickness of the lithosphere coincides with the value estimated from data of magnetotelluric sounding here. This indicates that formation time (36 Ma) of the South Okhotsk depression was estimated correctly. Numerical modeling performed for determination of the basement age of rifting basins in the Sea of Okhotsk gave the following estimates: 18 Ma (Early Miocene) for the Deryugin Basin, 12 Ma (Middle Miocene) for the TINRO Basin, and 23 Ma (Late Oligocene) for the West Kamchatka Trough. These estimates agree with formation time (Oligocene-Quaternary) of the sedimentary cover in rifting basins of the Sea of Okhotsk derived from geological and geophysical data. Model temperature estimates are obtained for lithologic and stratigraphic boundaries of the sedimentary cover in the Deryugin and TINRO Basins and the West Kamchatka Trough; the temperature analysis indicates that the latter two structures are promising for oil and hydrocarbon gas generation; the West Kamchatka Trough possesses better reservoir properties compared to the TINRO and Deryugin Basins. The latter is promising for generation of hydrocarbon gas. Paleogeodynamic reconstructions of the Sea of Okhotsk region evolution are obtained for times of 90, 66, and 36 Ma on the base of kinematic, geomagnetic, structural, tectonic, geothermal, and other geological and geophysical data.

Palynology and dinoflagellate counts of surface sediments, and sea surface conditions, of sites in the North Pacific

Palynological analyses were performed on 53 surface sediment samples from the North Pacific Ocean, including the Bering and Okhotsk Seas (37-64°N, 144°E-148°W), in order to document the relationships between the dinocyst distribution and sea-surface conditions (temperatures, salinities, primary productivity and sea-ice cover). Samples are characterized by concentrations ranging from 18 to 143816 cysts/cm**3 and the occurrence of 32 species. A canonical correspondence analysis (CCA) was carried out to determine the relationship between environmental variables and the distribution of dinocyst taxa. The first and second axes represent, respectively, 47% and 17.8% of the canonical variance. Axis 1 is positively correlated with all parameters except to the sea-ice and primary productivity in August, which are on the negative side. Results indicate that the composition of dinocyst assemblages is mostly controlled by temperature and that all environmental variables are correlated together. The CCA distinguishes 3 groups of dinocysts: the heterotrophic taxa, the genera Impagidinium and Spiniferites as well as the cyst of Pentapharsodinium dalei and Operculodinium centrocarpum. Five assemblage zones can be distinguished: 1) the Okhotsk Sea zone, which is associated to temperate and eutrophic conditions, seasonal upwellings and Amur River discharges. It is characterized by the dominance of O. centrocarpum, Brigantedinium spp. and Islandinium minutum; 2) the Western Subarctic Gyre zone with subpolar and mesotrophic conditions due to the Kamchatka Current and Alaska Stream inflows. Assemblages are dominated by Nematosphaeropsis labyrinthus, Pyxidinopsis reticulata and Brigantedinium spp.; 3) the Bering Sea zone, depicting a subpolar environment, influenced by seasonal upwellings and inputs from the Anadyr and Yukon Rivers. It is characterized by the dominance of I. minutum and Brigantedinium spp.; 4) the Alaska Gyre zone with temperate conditions and nutrient-enriched surface waters, which is dominated by N. labyrinthus and Brigantedinium spp. and 5) the Kuroshio Extension-North Pacific-Subarctic Current zone characterized by a subtropical and oligotrophic environment, which is dominated by O. centrocarpum, N. labyrinthus and warm taxa of the genus Impagidinium. Transfer functions were tested using the modern analog technique (MAT) on the North Pacific Ocean (= 359 sites) and the entire Northern Hemisphere databases ( = 1419 sites). Results confirm that the updated Northern Hemisphere database is suitable for further paleoenvironmental reconstructions, and the best results are obtained for temperatures with an accuracy of +/-1.7 °C.

Paleogene planktonic foraminifera of DSDP Hole 29-277

Stratigraphy of Paleogene deposits from high latitudes of the Pacific region (Koryak Highland, Kamchatka Peninsula, Karaginsky Island - in the northern hemisphere, Australian-Antarctic region - in the southern hemisphere) on planktonic foraminifera are under consideration in the book. Correlation with Paleogene of the warm Pacific belt is given. On the basis of geographic and stratigraphic distributions of planktonic foraminifera climatic zonation and the Paleogene climatic curve are analyzed. Description and photos of 115 species and varieties of planktonic foraminifera are given in the palaeontological part of the book.

Distribution and biomass of seston in the East Atlantic

Biomass of seston in the surface layers of coastal waters off Namibia reaches 1 g/m**2 and decreases with distance from the shore. Two regions of high seston biomass, one northern and one southern, are distinguished. A subsurface maximum of seston biomass, presumably coinciding with the stream of compensating countercurrent, is identified in the 200-500 m layer. Similar vertical distribution of plankton is known in upwelling areas of the eastern shores of the Atlantic and Pacific Oceans and in several other ocean areas, such as the area of the Kuril-Kamchatka Trench. This fact probably indicates that life cycles of pelagic animal forms of various taxonomic groups that inhabit them and phases of their ontogenic migrations are similar.

Activity of ETS enzymes and phosphatase in the Sea of Okhotsk and Kuril region in summer 1992 and 1993

An estimate of rate of transformation of organic matter and regeneration of nutrients (in particular phosphorus) was calculated for different regions of the Sea of Okhotsk. The rate was estimated by means of rate of complete oxidation of organic matter to CO2 and H2O catalyzed by enzymes of the electron transport system (ETS) and rate of hydrolytic splitting of phosphate from organic phosphorus compounds catalyzed by alkaline phosphatase. Organic matter destruction rate was at its maximum on the shelf of Kamchatka and Sakhalin, as well as in the layer of maximum oxygen gradients in deep waters. It was found that zones of intensive primary production were characterized by high rates of phosphorus regeneration, which provided for 80% of primary production when concentration of mineral phosphorus was low.