Total number of benthic foraminifera in sediments below the K/T boundary in the Atlantic and Pacific Ocean

Most species of Late Cretaceous deep-sea benthic foraminifera are believed to be cosmopolitan and therefore to exhibit only minor biogeographical differences. In this preliminary report, six Deep Sea Drilling Project (DSDP) sites from different oceans, paleolatitudes, and paleodepths were analyzed for terminal Cretaceous abyssal-bathyal benthic foraminifera in order to investigate their assumed cosmopolitan distribution and the question of whether different faunal compositions are related to time, different paleolatitudes, and/or different paleodepths. The material studied was obtained from the low-latitude Site 465 (Pacific Ocean), and the intermediate-latitude Sites 384 (North Atlantic) and 356, 516, 525, and 527 (South Atlantic). The material analyzed represents a time slice encompassing the last 20-50 k.y. of the Cretaceous. The faunas contain numerous "Velasco-type" species, such as Gavelinella beccariiformis (White), Cibicidoides velascoensis (Cushman), Nuttallides truempyi (Nuttall), Gaudryina pyramidata Cushman, and various gyroidinoids and buliminids. The results contradict the general assumption of the cosmopolitan nature of Late Cretaceous deep-sea benthic foraminifera advocated in the literature. Only about 9% of the taxa identified were found to be truly "cosmopolitan" through their occurrence at all the sites analyzed. On the basis of correspondence analysis and relative abundance data, three assemblages and three subassemblages were recognized: (1) a bathyal-abyssal assemblage [Nuttallinella sp. A, Cibicidoides hyphalus (Fisher), Valvalabamina sp. evolute form, and Gyroidinoides spp.] at the South Atlantic Sites 356, 516, 525, and 527, divided into three subassemblages, namely (a) a middle bathyal subassemblage [Eouvigerina subsculptura McNeil and Caldwell, Truaxia aspera (Cushman), and G. pyramidata] at Sites 516 and 525, (b) a lower bathyal subassemblage [Osangularia? sp., Pyramidina rudita (Cushman and Parker), and Quadrimorphina camerata (Brotzen)] at Site 356, and (c) an abyssal subassemblage [Gyroidinoides sp. C, Hyperammina-Bathysiphon, Gyroidinoides beisseli (White), and Globorotalites sp. B] at Site 527; (2) an abyssal assemblage [Buliminella cf. plana (Cushman and Parker) and Bulimina incisa Cushman] at the North Atlantic Site 384; and (3) a middle bathyal assemblage [Vulvulina sp. A, Osangularia navarroana (Cushman), Alabamina? sp., Bulimina velascoensis (Cushman), Spiroplectammina spp. calcareous forms, and Bulimina trinitatensis Cushman and Jarvis] at the Pacific Site 465.

Paleocene-Eocene calcareous nannofossils of onshore wells from the Coastal Plain of New Jersey and Maryland, USA

Paleogene calcareous nannofossils from split spoon cores recovered from five wells along the Coastal Plain of New Jersey and Maryland have been analyzed in order to provide onshore information complementary to that derived from the offshore DSDP Site 605 (upper continental rise off New Jersey). Hiatuses are more numerous and of greater extent in the onshore sections, but the major ones correlate well with those noted in the offshore section. At one site at least (Leggett Well), sedimentation may well have been continuous across the Cretaceous/Tertiary boundary, as it is believed to have been at DSDP Site 605. These various correlations are discussed elsewhere in a companion paper (Olsson and Wise, this volume). Important differences in nannofossil assemblages are noted between the onshore (shelf paleoenvironment) and offshore (slope-rise paleoenvironment) sections. Lithostromation simplex, not present offshore, is consistently present onshore and seems to be confined to the Eocene shelf sediments of this region. The same relationship holds for the zonal marker, Rhabdosphaera gladius Locker. The Rhomboaster-Tribrachiatus plexus is more diverse and better preserved in the onshore sections, where the lowermost Eocene Zone CP9 is well represented. Differential preservation is postulated to account for two morphotypes of Tribrachiatus bramlettei (Brönnimann and Stradner). Type A is represented at DSDP Site 605 by individuals with short, stubby arms, but these forms are not present in the equivalent onshore sections. There they are replaced by the Type B morphotypes, which exhibit a similar basic construction but possess much longer, more delicate arms.

Paleogene calcareous nannofossil biostratigraphy of DSDP Hole 21-210

The major objectives of Leg 133 were (1) to define the evolution of the carbonate platforms on the northeastern Australian margin, including their relationship to adjoining basins; and (2) to understand the effects of climate and sea level on their development in space and time (Davies, McKenzie, Palmer-Julson, et al., 1991, doi:10.2973/odp.proc.ir.133.1991). Sixteen sites were drilled, and more than 5.5 km of Neogene core was recovered during Leg 133. However, recovery of Paleogene sediments was unexpectedly poor (a total of a few meters), and the sediments were poorly dated because of strong diagenesis. On the other hand, Site 210 drilled in this region during Leg 21 yielded an expanded Paleogene section, which contains abundant calcareous microfossils. Biostratigraphic information for this section given in Burns, Andrews, et al. (1973, doi:10.2973/dsdp.proc.21.1973) was based primarily on shipboard results. Detailed calcareous nannofossil and planktonic foraminifer biostratigraphies have not been published. Here we provide a detailed documentation of the calcareous nannofossil distribution in the section, biostratigraphically date the section using the modern nannofossil zonation of Okada and Bukry (1980. doi:10.1016/0377-8398(80)90016-X), and construct an age-depth curve based on current knowledge of nannofossil magnetobiochronology. This should provide a useful Paleogene biostratigraphic reference in the northeastern Australian sea, as Site 210 has apparently yielded the most complete Paleogene record in the region. The detailed biostratigraphy should provide a better age constraint for the regional Eocene-Oligocene hiatus recognized previously (e.g., Jenkins and Srinivasan, 1986, doi:10.2973/dsdp.proc.90.113.1986) and should be useful for future studies on various aspects of Paleogene history of the northeastern Australian sea.

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.

Tertiary and Quaternary calcareous nannoplankton biostratigraphy of ODP Leg 112 holes

Positions of all cores recovered during Ocean Drilling Program (ODP) Leg 112 off Peru are shown in the standard calcareous nannoplankton zonation. Stratigraphic and regional occurrences and preservation of calcareous nannoplankton are discussed for all sites, and fossil lists are presented for selected samples. Late Miocene to Holocene nannoplankton assemblages in the upwelling systems off Peru and scattered blooms, especially of Gephyrocapsa species and Helicosphaera carteri, are described. Scyphosphaera assemblages found in late Miocene Zone NN9 {Discoaster hamatus Zone) at Site 684 are compared with similar assemblages from Gabon on the west coast of Africa. Remarkable subsidence is indicated by early and middle Eocene nearshore and shallow-water nannoplankton assemblages for Sites 682, 683, and 688. Besides several local hiatuses, major regional hiatuses were noted at Site 682 (upper Eocene, uppermost middle Eocene, and part of the lower and middle Oligocene missing), Site 683 (uppermost middle Eocene to lower part of the middle Miocene missing), and Site 688 (part of the middle Eocene, uppermost middle Eocene to upper Oligocene, and parts of the lower and middle Miocene missing).

Siliceous microplankton in surface sediments and the water column of the Red Sea

We studied the siliceous microplankton assemblages (mainly diatoms) from plankton tows (mesh size 20 µm) and surface sediment samples collected along a N-S transect in the northern Red Sea (28-21°N). In addition, we analyzed differences/similarities between plankton and sediment assemblages within a brine-filled basin (the southern basin) of the Shaban Deep and compared these assemblages with those from outside the brine. Plankton samples revealed the overwhelming dominance of diatoms over other siliceous groups. Diatoms accounted for ca. 97% of all biosiliceous particles at 120-20 m (vs. 2.9% silicoflagellates and 0.4% radiolarians), and ca. 94% at 200-120 m (vs. 4.5% silicoflagellates and 1.6% radiolarians). In general, a marine, warm-water (tropical/subtropical) diatom assemblage characterizes the plankton samples. Representatives of the Nitzschia bicapitata group are by far the most abundant contributors at both depth intervals (average=43%), ranging from ca. 30% in the North to ca. 60% in the South. Biogenic opal content in non-brine surface sediments is very low, (below 0.2 wt.% SiO2); and concentration of siliceous microorganisms is also low and of the order of 5*10**3-10**4 microorganisms/g dry sediment. Diatoms are the main contributors to the opal signal in the 20-40 µm fraction, while they share dominance with radiolarians in the >40 µm fraction. Total diatom concentrations average 1.2*10**4 valves/g in the 20-40 µm fraction and 4*10**3 valves/g in the >40 µm fraction. Robust taxa of warm water affinity (Alveus marinus, Azpeitia neocrenulata, Azpeitia nodulifera and Roperia tesselata) characterize the surface sediments. In contrast, biogenic opal content in brine surface sediment samples is much higher than in the non-brine samples, ranging from 2.8 to 3.8 wt.% SiO2, and concentration of siliceous microorganisms is 3-4 orders of magnitude higher. In addition here, diatoms dominate the opal signal. The taxa found in these samples are a mixture of non-brine and plankton samples, and fragile forms (e.g., N. bicapitata group, Neodelphineis indica) are well preserved in these sediments. Thus, brine sediments in this region seem to offer a great potential for palaeoenvironmental studies.