Living benthic foraminiferal assemblages in surface samples of the Arabian Sea

The distribution, biomass, and diversity of living (Rose Bengal stained) deep-sea benthic foraminifera (>30 µm) were investigated with multicorer samples from seven stations in the Arabian Sea during the intermonsoonal periods in March and in September/October, 1995. Water depths of the stations ranged between 1916 and 4425 m. The distribution of benthic foraminifera was compared with dissolved oxygen, % organic carbon, % calcium carbonate, ammonium, % silica, chloroplastic pigment equivalents, sand content, pore water content of the sediment, and organic carbon flux to explain the foraminiferal patterns and depositional environments. A total of six species-communities comprising 178 living species were identified by principal component analysis. The seasonal comparison shows that at the western stations foraminiferal abundance and biomass were higher during the Spring Intermonsoon than during the Fall Intermonsoon. The regional comparison indicates a distinct gradient in abundance, biomass, and diversity from west to east, and for biomass from north to south. Highest values are recorded in the western part of the Arabian Sea, where the influence of coastal and offshore upwelling are responsible for high carbon fluxes. Estimated total biomass of living benthic foraminifera integrated for the upper 5 cm of the sediment ranged between 11 mg Corg m**-2 at the southern station and 420 mg Corg m**-2 at the western station. Foraminifera in the size range from 30 to 125 ?m, the so-called microforaminifera, contributed between 20 and 65% to the abundance, but only 3% to 28% to the biomass of the fauna. Highest values were found in the central and southern Arabian Sea, indicating their importance in oligotrophic deep-sea areas. The overall abundance of benthic foraminifera is positively correlated with oxygen content and pore volume, and partly with carbon content and chloroplastic pigment equivalents of the sediment. The distributional patterns of the communities seem to be controlled by sand fraction, dissolved oxygen, calcium carbonate and organic carbon content of the sediment, but the critical variables are of different significance for each community.

The Global Plankton Database: an inventory and data from the Former Soviet Union expeditions

At present time, there is a lack of knowledge on the interannual climate-related variability of zooplankton communities of the tropical Atlantic, central Mediterranean Sea, Caspian Sea, and Aral Sea, due to the absence of appropriate databases. In the mid latitudes, the North Atlantic Oscillation (NAO) is the dominant mode of atmospheric fluctuations over eastern North America, the northern Atlantic Ocean and Europe. Therefore, one of the issues that need to be addressed through data synthesis is the evaluation of interannual patterns in species abundance and species diversity over these regions in regard to the NAO. The database has been used to investigate the ecological role of the NAO in interannual variations of mesozooplankton abundance and biomass along the zonal array of the NAO influence. Basic approach to the proposed research involved: (1) development of co-operation between experts and data holders in Ukraine, Russia, Kazakhstan, Azerbaijan, UK, and USA to rescue and compile the oceanographic data sets and release them on CD-ROM, (2) organization and compilation of a database based on FSU cruises to the above regions, (3) analysis of the basin-scale interannual variability of the zooplankton species abundance, biomass, and species diversity.

Stratigraphic distribution of marine palynomorph species recorded for the Miocene of ODP Hole 105-645E (Table 1)

A total of 145 samples were analyzed for palynology, and all were found to be productive. Residues are dominated by pollen, terrestrial spores, and land plant tissues. Marine palynomorphs occur in all samples, which allowed us to recognize five Miocene dinocyst assemblage zones. Dinocyst assemblages indicate cool-water conditions and suggest a neritic rather than fully oceanic environment, with not only North Atlantic and Norwegian Sea affinities, but also containing both notable protoperidiniacean and possible endemic elements. Dinocyst assemblages indicate an early Miocene age for the bottom of Hole 645E and an age no younger than early late Miocene (Sample 105-645E-24R, CC) near the top of the interval studied. These age assignments provide an estimated initiation of ice rafting in Baffin Bay at between 7.4 and 9.5 Ma. Increased terrigenous influx and apparent disappearance of certain dinocyst taxa occur in the middle to late Miocene and may be related to oceanographic changes or climatic deterioration. Spores and pollen indicate a climate that varied within a temperate regime during the early and middle to early late Miocene, followed by climatic deterioration. Four new dinocyst species are described: Batiacasphaera gemmata, Impletosphaeridium prolatum, Operculodinium vacuolatum, and Selenopemphix brevispinosa. The acritarch genus Cyclopsiella Drugg and Loeblich is emended, and two new combinations have been created: Cyclopsiella granosa (Matsuoka) and Cyclopsiella? laevigata (Chateauneuf). Cyclopsiella granosa (Matsuoka) n. comb. is considered a subjective junior synonym of Cyclopsiella granulata He and Li. Ascostomocystis granulatus Chateauneuf has been provisionally allocated to Cyclopsiella and renamed Cyclopsiella? chateauneufii. Two new acritarch species are described: Cyclopsiella spiculosa and Cymatiosphaera! baffinensis.

Miocene through Pleistocene dinoflagellates from ODP Site 170-1039

Palynological data from offshore Costa Rica, allow us to investigate the relationship between dinoflagellate cyst assemblages and changes in regional oceanic primary productivity. From Miocene to Pleistocene, productivity at ODP Site 1039 was influenced by tectonic drift, as Site 1039 approached the continent, from the Equator to its current position at ~10°N. In addition, dinoflagellate abundance is modulated by regional productivity events, which modified primary productivity, as also indicated by available data on calcareous nannofossils, diatoms, TOC, and CaCO3 content. Five palynomorph intervals are defined. The early-late Miocene one, dominated by Batiacasphaera, represents relatively stable, productive oceanic conditions before the closure of the Indonesian and Panama Seaways. The late Miocene decrease in palynomorph recovery is related to the Carbonate Crash Event. The high abundance and diversity of the assemblages at the end of the late Miocene to early Pliocene indicate increased productivity related to the Global Biogenic Bloom, and a change in dominance from Batiacasphaera to Impagidinium to Nematosphaeropsis. The low abundance of the late Pliocene interval is related to El Niño-like conditions, and there is another change related to the disappearance of Batiacasphaera and dominance of Impagidinium, Nematosphaeropsis, and Operculodinium. The abundant Pleistocene assemblages represent increased marine productivity, and a high influx of continental palynomorphs and bissacate pollen, associated with the proximity of the Costa Rica Dome. Pleistocene dinoflagellates are characterized by Spiniferites and Selenopemphix, together with rare Impagidinium and Nematosphaeropsis.

Distribution of foraminifera and other components in ODP Leg 188 sites

During Leg 188 of the Ocean Drilling Program (ODP), employing JOIDES Resolution, we drilled holes at three sites in the southern Indian Ocean in and near Prydz Bay, East Antarctica, between 28 January and 29 February 2000. The objectives of the voyage were to: - Core through sediments deposited when Antarctica underwent the transition from "greenhouse" to the modern "icehouse" state late in the Eocene or early in the Oligocene, at sites obtaining their sediment from the currently subglacial Gamburtsev Mountains that probably were the site of nucleation of the ice sheet (principally Site 1166); - Obtain a sediment record from times at which major changes in the ice sheet volume and characteristics took place as judged from oxygen isotope records, especially at ~23.7 Ma (Oligocene/Miocene boundary), 12-16 Ma (middle Miocene), and 2.7 Ma (late Pliocene) (mainly Site 1165); and - Sample through the upper Pliocene and Quaternary in an attempt to document fluctuations in the extent of the ice sheet over the continental shelf during the Quaternary (especially Site 1167). Paleogene foraminifer-bearing marine sections were not intersected, and thus discussion of marine sections is restricted to the Neogene. Foraminifers are not major contributors to Leg 188 chronostratigraphy but contribute to paleoenvironmental interpretation, to issues such as carbonate compensation depth (CCD) effects and source and history of sediment, and provide a basis for Sr and d18O studies. Chronostratigraphy for the various sections was compiled from diatoms, radiolarians, and paleomagnetism (Shipboard Scientific Party, 2001, doi:10.2973/odp.proc.ir.188.101.2001). Foraminifers were sporadic rather than continuous except in short intervals; however, the Neogene foraminifers from the region are very poorly known and the new records proved to be of significant value in paleoenvironmental interpretation. Only at Site 1167 did drilling intersect a section that yielded foraminifers virtually throughout. Other than for the very young section at each site, there is virtually no continuity of assemblages between sites and thus each section is treated here as separate and unrelated.

Bolboforma abundance in ODP Hole 162-982A and DSDP Hole 12-116 sediments

Although they are fossils of uncertain origin, bolboforms are the best calcareous microfossil group for Neogene biostratigraphy in the North Atlantic. Fifty-two Bolboforma species were observed at the Hatton-Rockall Basin in Ocean Drilling Program Holes 982A (26 samples) and 982B (301 samples) and in Deep Sea Drilling Project Hole 116 (71 samples). The sequence investigated spans the interval from lower Miocene to upper Pliocene. Fourteen zones/subzones were identified and correlated with the calcareous nannoplankton zones, the planktonic foraminifer biostratigraphy, and the time (Ma). The last occurrence of the genus Bolboforma can be dated to 2.84 Ma. Different Bolboforma specimens of middle Miocene age, observed in upper Miocene and upper middle Miocene sediments at Site 982, document redeposition of sediment from the Rockall Bank into the Hatton-Rockall Basin during the latest middle Miocene and late Miocene.

Miocene foraminiferal, bolboformid, dinoflagellate and diatom age calibrations for the northeastern North Atlantic

This study presents a new Miocene biostratigraphic synthesis for the high-latitude northeastern North Atlantic region. Via correlations to the bio-magnetostratigraphy and oxygen isotope records of Ocean Drilling Program and Deep Sea Drilling Project Sites, the ages of shallower North Sea deposits have been better constrained. The result has been an improved precision and documentation of the age designations of the existing North Sea foraminiferal zonal boundaries of King (1989) and Gradstein and Bäckström (1996). All calibrations have been updated to the Astronomically Tuned Neogene Time Scale (ATNTS) of Lourens et al. (2004). This improved Miocene biozonation has been achieved through: the updating of age calibrations for key microfossil bioevents, identification of new events, and integration of new biostratigraphic data from a foraminiferal analysis of commercial wells in the North Sea and Norwegian Sea. The new zonation has been successfully applied to two commercial wells and an onshore research borehole. At these high latitudes, where standard zonal markers are often absent, integration of microfossil groups significantly improves temporal resolution. The new zonation comprises 11 Nordic Miocene (NM) Zones with an average duration of 1 to 2 million years. This multi-group combination of a total of 92 bioevents (70 foraminifers and bolboformids; 16 dinoflagellate cysts and acritarchs; 6 marine diatoms) facilitates zonal identification throughout the Nordic Atlantic region. With the highest proportion of events being of calcareous walled microfossils, this zonation is primarily suited to micropaleontologists. A correlation of this Miocene biostratigraphy with a re-calibrated oxygen isotope record for DSDP Site 608 suggests a strong correlation between Miocene planktonic microfossil turnover rates and the inferred paleoclimatic trends. Benthic foraminifera zonal boundaries appear to often coincide with Miocene global sequence boundaries. The biostratigraphic record is punctuated by four main stratigraphic hiati which show variation in their geographic and temporal extent. These are related to the following regional unconformities: basal Neogene, Lower/Middle Miocene ("mid-Miocene unconformity"), basal Upper Miocene and basal Messinian unconformities. Further coring of Neogene sections in the North Sea and Norwegian Sea may better constrain their extent and their effect on the biostratigraphic record.

Composition and age of bottom sediments from the Southern Ocean

Geomorphology, geology, stratigraphy, lithology and geochemistry of bottom sediments in the South Ocean are under consideration. Regularities of distribution of iron-manganese nodules, features of occurrence of ore components in the nodules, nodule abundance in bottom sediments have been studied.