Water, bottom deposits, and macrobenthos in the south part of the East Siberian Sea in September 2003

Macrobenthos biomass and bottom biocoenoses were studied in the sublittoral zone of the southern East Siberian Sea. The macrobenthos is characterized by relatively high abundance (from 30 to 2680 #/m**2), biomass (from 0.25 to 578.8 g/m**2), and diversity (83 species in total). Lateral distribution of macrobenthos biomass correlates with a substrate type and salinity and is substantially higher in areas washed by the Arctic water mass than in estuaries with mixed fresh and Arctic waters and shows a tendency to decreasing in the convergence zone of different water masses. The highest macrobenthos biomass is observed in cores of water masses in the Long Strait area and in the eastern part of the sea.

Nannofossil datums and abundance in sediments from ODP Leg 164 sites

Twenty routinely used nannofossil datums in the late Neogene and Quaternary were identified at three Blake Ridge sites drilled during Leg 164. The quantitative investigation of the nannofossil assemblages in 236 samples selected from Hole 994C provide new biostratigraphic and paleoceanographic information. Although mostly overlooked previously, Umbilicosphaera aequiscutum is an abundant component of the late Neogene flora, and its last occurrence at ~2.3 Ma is a useful new biostratigraphic event. Small Gephyrocapsa evolved within the upper part of Subzone CN11a (~4.3 Ma), and after an initial acme, it temporarily disappeared for 400 k.y., between 2.9 and 2.5 Ma. Medium-sized Gephyrocapsa evolved in the latest Pliocene ~2.2 Ma), and after two short temporary disappearances, common specimens occurred continuously just above the Pliocene/Pleistocene boundary. The base of Subzone CN13b should be recognized as the beginning of the continuous occurrence of medium-sized (>4 µm) Gephyrocapsa. Stratigraphic variation in abundance of the very small placoliths and Florisphaera profunda alternated, indicating potential of the former as a proxy for the paleoproductivity. At this site, it is likely that upwelling took place during three time periods in the late Neogene (6.0-4.6 Ma, 2.3-2.1 Ma, and 2.0-1.8 Ma) and also in the early Pleistocene (1.4-0.9 Ma). Weak upwelling is also likely to have occurred intermittently through the late Pliocene. Due to the sharp and abrupt turnover of the nannofossils, which resulted from an evolution of very competitive species, the paleoproductivity of the late Pleistocene is not clear. The site was mostly in an oligotrophic central gyre setting during the 4.6- to 2.3-Ma interval, intermittently between 2.1 and 1.4 Ma, and continuously for the last several tens of thousand years.

Lecturas y escrituras : La literatura como metatexto

Fil: Brunelli, Anahí Adelaida. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Literatura y TICs : Dos herramientas valiosas para estimular la producción oral y escrita

Fil: Gargiulo, Sandra Beatriz. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Age determination, planktic foraminifera and stable istopes of sediment core MSM05/5_712-2

A sediment core from the West Spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last ~9 ka in the eastern Fram Strait. Our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern Fram Strait occurred stepwise, in response to the postglacial sea-level rise and the related onset of modern sea-ice production on the shallow Siberian shelves. The late Early and Mid Holocene interval (9 to 5 ka) was generally characterized by relatively unstable conditions. High abundance of the subpolar planktic foraminifer species Turborotalita quinqueloba implies strong intensity of Atlantic Water (AW) inflow with high productivity and/or high AW temperatures, resulting in a strong heat flux to the Arctic. A series of short-lived cooling events (8.2, 6.9. and 6.1 ka) occurred superimposed on the warm late Early and Mid Holocene conditions. Our proxy data imply that simultaneous to the complete postglacial flooding of Arctic shallow shelves and the initiation of modern sea-ice production, strong advance of polar waters initiated modern oceanographic conditions in the eastern Fram Strait at ~5.2 ka. The Late Holocene was marked by the dominance of the polar planktic foraminifer species Neogloboquadrina pachyderma, a significant expansion of sea ice/icebergs, and strong stratification of the water column. Although planktic foraminiferal assemblages as well as sea surface and subsurface temperatures suggest a return of slightly strengthened advection of subsurface Atlantic Water after 3 ka, a relatively stable cold-water layer prevailed at the sea surface and the study site was probably located within the seasonally fluctuating marginal ice zone during the Neoglacial period.

Lecturas y escrituras : La literatura como metatexto

Fil: Brunelli, Anahí Adelaida. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Literatura y TICs : Dos herramientas valiosas para estimular la producción oral y escrita

Fil: Gargiulo, Sandra Beatriz. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Sedimentology and Lead and Strontium isotope ratios of Miocene sediments from the Kerguelen Plateau

Characterization of sediment from Ocean Drilling Program Site 745, representing the East Kerguelen Ridge sediment drift, addresses important issues surrounding the timing of Miocene to present East Antarctic ice sheet stability and oceanic environmental change. Our results show three periods of greatly enhanced accumulation of Antarctic-derived sediment, at 6.4-5.9 Ma, 4.9-4.4 Ma and 1.1-0.8 Ma, potentially indicative of warmer, less stable ice sheets at these times. Conversely, the accumulation of Antarctic-derived material is comparatively less during the middle of the Pliocene warm epoch (4.8-3.2 Ma). The deep flow forming the Kerguelen drift was stronger during the latest Miocene and earliest Pliocene and has decreased in intensity continuously since then.

Production characteristics and water parameters of the Kola Bay in 2004-2005

Data on chlorophyll a concentration and phytoplankton primary production in the south Kola Bay in 2004-2005 are given.

Lecturas y escrituras : La literatura como metatexto

Fil: Brunelli, Anahí Adelaida. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.