Cretaceous calcareous nannofossils of ODP Leg 103 holes

Ocean Drilling Program Leg 103 recovered Lower Cretaceous sediments from the Galicia margin off the coast of Iberia. The high diversity and abundance of assemblages makes this excellent material for the study of Early Cretaceous calcareous nannofossils. With the exception of a hiatus between the upper Hauterivian and lower Barremian, nannofossil distributions form a continuous composite section from the lower Valanginian to lower Cenomanian sediments recovered at the four sites. The sedimentation history of this rifted continental margin is complex, and careful examination of the nannofossil content and lithology is necessary in order to obtain optimum biostratigraphic resolution. The Lower Cretaceous sequence consists of a lower Valanginian calpionellid marlstone overlain by terrigenous sandstone turbidites deposited in the Valanginian and Hauterivian during initial rifting of this part of the margin. Interbedded calcareous marl and claystone microturbidites overlie the sandstone turbidites. Rifting processes culminated in the late Aptian-early Albian, resulting in the deposition of a calcareous, clastic turbidite sequence. The subsequent deposition of dark carbonaceous claystones (black shales) represents the beginning of seafloor spreading, as the margin continued to subside to depths near or below the CCD. The diversity, abundance, and preservation of nannofossils within these varied lithologies differ, and an attempt to distinguish between near shore and open-marine assemblages is made. Genera used for this purpose include Nannoconus, Micrantholithus, Pickelhaube, and Lithraphidites. In this study, six new species and one new subspecies are described and documented. Ranges of other species are extended, and an attempt is made to clarify existing, yet poorly understood, taxonomic concepts. A technique in which a single specimen is viewed with both light and scanning electron microscopes was used extensively to aid in this task. In addition, further subdivisions of the Sissingh (1977) zonation are suggested in order to increase biostratigraphic resolution.

Planktic foraminiferal turnover across the Paleocene-Eocene transition in the Bay of Biscay, North Atlantic

Planktic foraminifera across the Paleocene-Eocene transition at DSDP Site 401 indicate that the benthic foraminiferal mass extinction occurred within Subzone P 6a of Berggren and Miller (1988), or PS of Berggren et al. (1995) and coincident with a sudden 2.0? excursion in 6r3C values. The benthic foraminiferal extinction event (BFEE) and Sr3C excursion was accompanied by a planktic foraminiferal turnover marked by an influx of warm water species (Morozovella and Acarinina), a decrease in cooler water species (Subbotina), a sudden short-term increase in low oxygen tolerant taxa (Chiloguembelina), and no significant species extinctions. These faunal changes suggest climatic warming, expansion of the oxygen minimum zone, and a well stratified ocean water column. Oxygen isotope data of the surface dweller M. subbotina suggest climate warming beginning with a gradual 0.5? decrease in delta180 in the 175 cm preceding the benthic foraminiferal extinction event followed by a sudden decrease of 1? (4°C) at the BFEE. The delta13C excursion occurred over 27 cm of sediment and, assuming constant sediment accumulation rates, represents a maximum of 23 ka. Recovery to pre-excursion delta13C values occurs within 172 cm, or about 144 ka. Climate cooling begins in Subzone P 6c as indicated by an increase in cooler water subbotinids and acarininids with rounded chambers and a decrease in warm water morozovellids.

Abundance of mesozooplankton collected in October and November 1991 at 20 stations in the South Aegean Sea during O91

The O91- Mesozooplankton dataset is based on samples collected in mid October-mid November 1991 at 20 stations in the South Aegean, the SE.Ionian Sea and in NW Levantine. Samples were collected at discrete layers (from the surface till 300m. These data are published. Sampling volume was estimated by multiplying the mouth area with the wire length. The entire sample (for deep layers) or aliquot of Taxon-specific mesozooplankton abundance (1/4) (for the upper layer) was analyzed under the binocular microscope. Copepod and cladoceran species were identified and enumerated; the other zooplankters were identified and enumerated at higher taxonomic level (commonly named as zooplankton groups). Taxonomic identification was done by I.Siokou-Frangou, E.Christou, and N.Fragopoulu, using the relevant taxonomic literature. The entire sample (for deep layers) or aliquot of Mesozooplankton total abundance (1/4) (for the upper layer) was analyzed under the binocular microscope. All zooplankters were enumerated.

Abundance and biomass of mesozooplankton from the S-R01 cruise in the western part of the Black Sea in April 2008

The SESAME dataset contains mesozooplankton data collected during April 2008 in the North-West Black Sea (between 44°46' N and 42°29'N latitude and 28°64'E and 30°59'E longitude). Mesozooplankton sampling was undertaken at 9 stations where samples were collected using a Nansen closing net in the 0-10, 10-25, 25-50, 50-100, 100-150, 150-180 m layer. The dataset includes 28 samples analysed for mesozooplankton species composition, species abundance and total biomass. The Taxon-specific mesozooplankton abundance sample or aliquots were analyzed under the binocular microscope. Taxonomic identification was done according to Morduhai-Boltovskii et al. 1968. Total biomass was estimated using a tabel with wet weight for each species an stage (Petipa method).

Neogene planktonic foraminifera of DSDP Leg 41 holes

During Leg 41 Neogene sediments were recovered from five sites off northwest Africa. On the Sierra Leone Rise (Site 366), Neogene sediments consist of nanno oozes, nanno chalk, and calcareous clays 230 meters thick, resting conformably on the late Oligocene sediments. The common succession of zones occurs with two hiatuses. The lower gap corresponds to an interval around the lower/middle Miocene boundary (the Praeorbulina glomerosa and Orbulina suturalis-Globorotalia peri-pheroronda zones are absent) and the upper gap coincides with an interval around the middle/upper Miocene boundary (the Sphaeroidinellopsis sub-dehiscens-GIobigerina druryi, Globigerina nepenthes-Globorotalia siakensis and Globorotalia conlinuosa zones are missing). In the Cape Verde Basin (Site 367) deep-water Neogene turbidites (about 200-250 m thick) contain poor fauna of redeposited and sorted Cretaceous, Eocene, Oligocene, and Neogene species. On the Cape Verde Rise (Site 368) the Neogene section starts with slightly calcareous and non-calcareous clays with poor planktonic foraminifers of the lower Miocene. Later on this area was uplifted and clayey sediments have been replaced upsection in order by more shallow-water clayey nanno and nanno-foraminifer oozes and marls and pure calcareous oozes. In the middle Miocene, planktonic foraminifers are still not diverse, but since the level of the Globigerina nepenthes-Globorotalia siakensis Zone, almost all Neogene zones have been traced. The minimum thickness of the Neogene sediments is about 230 meters. On the continental slope off Spanish Sahara (Site 369) monotonous calcareous pelagic sediments of Neogene age (164 m thick) overlie the late Oligocene comformably, or with a small time gap. A set of zones beginning from the Globigerinoides primordis-Globorotaiia kugleri Zone up to the Globorotalia fohsi fohsi Zone has been revealed with a gap corresponding to the Globigerinita stainforthi and the Globigerinatella insueta-Globigerinoides irilobus zones. Above that follow sediments with heterogeneous microfauna which result from redeposition or mixing of sediments during drilling. The section ends with sediments of the late Miocene and lower Pliocene with abundant planktonic foraminifers. The latter are unconformably overlain by the Quaternary ooze. In the Morocco basin (Site 370) deep-water marls and calcareous clays of the lower Miocene contain poor assemblages of planktonic foraminifers. The middle and upper Miocene are represented by turbidites (alternation of nanno oozes, clays, siltstones, and sands) with heterogeneous microfauna. Total thickness of Neogene is up to 200 meters. In general the Neogene foraminifer microfauna of the area studied includes the majority of species which developed within the tropical-subtropical belt. The entire succession of the Miocene and Pliocene foraminifer zones occurs. The only exclusion is the Sphaeroidinellopsis subdehiscens-Globigerina druryi Zone of the middle Miocene. The distribution of species is shown on three tables. Comments are given for 47 species and subspecies of foraminifers (stratigraphic ranges, peculiarities of morphology, and ultrastructure of the shell wall).