Dinoflagellate cysts of the Early Cretaceous North Atlantic Ocean

Early Cretaceous dinoflagellate cysts were reinvestigated from nine deep-sea sites of the North and Central Atlantic. In general the zonation scheme developed for the western Central Atlantic (Habib, 1977; Habib and Drugg, 1983 ) can also be applied to the eastern Central Atlantic. Comparison with the probabilistic zonation of Gradstein et al. (1992) show, however, that the first occurrences of the important marker species Druggidium apicopaucicure, Druggidium deflandrei, Druggidium rhabdoreticulatum and Odontochitina operculata appear to occur slightly later in the eastern Central Atlantic in respect to nannofossils and benthic foraminifers. Muderongia neocomica has a shorter stratigraphic range in the eastern Central Atlantic than in the western Central Atlantic.

Hydrocarbons in surface waters of the Atlantic and Indian Oceans

Results of investigation of various forms of oil pollution, i.e. oil films, tar, and hydrocarbons in the Northeast Atlantic Ocean and North Indian Ocean during October-December 1980 and February-May 1981 are presented. Oil pollution was found only in regions of the heaviest ship traffic and was somewhat less than in 1976-1977. Background concentration of non-polar hydrocarbons was 8-10 ?g/l in surface waters and 14 ?g/l in the shelf zone. Infrared spectroscopy and gas-liquid chromatography indicate that hydrocarbons occurring at concentrations exceeding 50 ?g/l have composition differing from background hydrocarbons. There is considerable accumulation of hydrocarbons in the thin surface layer, and they exist in different forms close to pollution sources.

Distribution of benthic foraminifera in lower Cretaceous sediments of the Cuvuer Abyssal Plain in the Indian Ocean

Analysis of 66 samples from DSDP Site 263 (Cores 263-4R-4 to 263-29R-4) reveals a unique faunal composition with a predominance of agglutinated taxa, many of them previously unrecorded from any other DSDP and ODP Indian Ocean sites. A total of 66 agglutinated and 31 calcareous taxa are documented and five new species are described: Hippocrepina gracilis n.sp., "Textuluriopsis" elegans n.sp., Aaptotoichus challengeri n.sp., "Gaudryinopsis" pseudobettenstaedti n.sp. and "Gaudryina" cuvierensis n.sp. Three assemblages are recognized based on changes in the composition of dominant taxa and occurrences of stratigraphically important species: (1) a high-diversity Valanginian to Barremian Bulbobaculites-Recurvoides Assemblage (Cores 263-29R to - 18R), comprised of numerous elongate agglutinated forms, rare nodosariids, and variable numbers of tubes and ammodiscids; (2) a moderately diverse Aptian to Albian Rhizammina-Ammodiscus-Glomospira Assemblage (Cores 263-18R to -7R) with highly fluctuating numbers of the nominate taxa and Haplophragmoides, Trochammina, Verneuilinoides spp., and Verneuilina howchini; (3) a very low diversity Albian or younger Assemblage (Cores 263-6R to -4R) containing sparse agglutinated foraminifera, rare nodosariids and rotaliids. We interpret the assemblages as shelf to lower slope and consider them to reflect a deepening palaeobathymetry as the Cuvier margin subsided after the initial breakup of East Gondwana during the Valanginian. Our interpretation is in sharp contrast with initial palaeodepth estimates of less than 100 m, as well as with original chronostratigraphic interpretations based on foraminifera and nannofossils which correlated the base of the recovered interval with the Aptian. The absence of many cosmoplitan forms, despite high diversity suggests strong faunal differentiation in the Austral realm or endemisn within the Cuvier Basin during the Early Cretaceous.

Phosphorus in bottom sediments and micronodules from Core VITYAZ7414, Central Indian Ocean

Study of phosphorus distribution in grain size fractions of eupelagic clays showed high (up to 3%) content of P in Fe-Mn micronodules that can contain up to 20-30% of total P. Mineral P associated with Fe in ocean sediments is an analog of manganese in ocean sedimentogenesis. Sharp decrease of P contents in ocean Fe-Mn nodules compared to ones from seas results from decrease of Fe contents and partial neutralization of Fe activity by Mn.

Investigation of the seasonality of N. pachyderma in the North Atlantic Ocean during Heinrich Stadial 1 using an ecosystem modeling approach

Fossil shells of planktonic foraminifera serve as the prime source of information on past changes in surface ocean conditions. Because the population size of planktonic foraminifera species changes throughout the year, the signal preserved in fossil shells is biased towards the conditions when species production was at its maximum. The amplitude of the potential seasonal bias is a function of the magnitude of the seasonal cycle in production. Here we use a planktonic foraminifera model coupled to an ecosystem model to investigate to what degree seasonal variations in production of the species Neogloboquadrina pachyderma may affect paleoceanographic reconstructions during Heinrich Stadial 1 (~18-15 cal. ka B.P.) in the North Atlantic Ocean. The model implies that during Heinrich Stadial 1 the maximum seasonal production occurred later in the year compared to the Last Glacial Maximum (~21-19 cal. ka B.P.) and the pre-industrial era north of 30 ºN. A diagnosis of the model output indicates that this change reflects the sensitivity of the species to the seasonal cycle of sea-ice cover and food supply, which collectively lead to shifts in the modeled maximum production from the Last Glacial Maximum to Heinrich Stadial 1 by up to six months. Assuming equilibrium oxygen isotopic incorporation in the shells of N. pachyderma, the modeled changes in seasonality would result in an underestimation of the actual magnitude of the meltwater isotopic signal recorded by fossil assemblages of N. pachyderma wherever calcification is likely to take place.