Upper Maestrichtian to Eocene benthic foraminifera in ODP Leg 121 holes

Late Maestrichtian to late Eocene bathyal benthic foraminiferal faunas at Sites 752,753, and 754 on Broken Ridge in the eastern Indian Ocean were analyzed as to their stratigraphic distribution of species to clarify the relation between faunal turnovers and paleoceanographic changes. Based on Q-mode factor analysis, eight varimax assemblages were distinguished: the Stensioina beccariiformis assemblage in the upper Maestrichtian to upper Paleocene; the Cibicidoides hyphalus assemblage in the upper Maestrichtian; the Cibicidoides cf. pseudoperlucidus assemblage in the upper Paleocene; the Anomalinoides capitatusldanicus assemblage in the uppermost Paleocene to lower Eocene; the Cibicidoides subspiratus assemblage in the lower Eocene; the Nuttallides truempyi assemblage in the lower and middle Eocene; the Osangularia sp. 1 - Hanzawaia ammophila assemblage in the upper Eocene; and the Lenticulina spp. assemblage in the uppermost Eocene, Oligocene, and lower Miocene. The presence of the Osangularia sp. 1 - Hanzawaia ammophila assemblage is related to the shallowing episode on Broken Ridge (upper bathyal), as a result of the rifting event that occurred in the middle Eocene. The most distinct faunal change (the disappearance of about 37% of the species) occurred between the S. beccariiformis assemblage and the A. capitatusldanicus assemblage, at the end of the upper Paleocene. A. capitatusldanicus, Lenticulina spp., and varied forms of Cibicidoides replaced the Velasco-type fauna at this time. The timing of this event is well correlated with the known age at South Atlantic sites (Thomas, 1990 doi:10.2973/odp.proc.sr.113.123.1990; Kennett and Stott, 1990 doi:10.2973/odp.proc.sr.113.188.1990; Katz and Miller, 1990 doi:10.2973/odp.proc.sr.114.147.1991). The primary cause of the extinction of the Stensioina beccariiformis assemblage is elusive, but may have resulted from the cessation of deep-water formation in the Antarctic (Katz and Miller, 1990), and subsequent arrival of warm saline deep water (Thomas, 1990; Kennett and Stott, 1990). Another possibility may be a weakened influence of high-salinity water formed at the low latitudes such as the Tethys Sea. The extinction event corresponds to the change from higher delta13C values in benthic foraminifers to lower ones. An interpretation of delta13C values is that the eastern Indian deep water, characterized by young and nutrient-depleted water, became old water which was devoid of a supply of new water during the latest Paleocene to early Eocene. Prior to this benthic event, signals of related faunal change were detected in the following short periods: early and late Paleocene, near the boundary of nannofossil Zone CP4, and Zone CP5 of the late Paleocene at Site 752. Among common taxa in the upper Maestrichtian, only seven species disappeared or became extinct at the Cretaceous/ Tertiary boundary at Site 752. The benthic foraminiferal population did not change for up to 2 m above the boundary, in contrast to the rapid decrease of the plankt onic foraminiferal population at the boundary. A decrease in the number of benthic foraminifers occurs after that level, corresponding to an interval of decreased numbers of planktonic foraminifers and higher abundance of volcanic ash. Reduced species diversity (H') suggests a secondary effect attributable to the dissolution of foraminiferal tests. The different responses of planktonic and benthic foraminifers to the event just above the boundary suggest that the Cretaceous/Tertiary event was a surface event as also suggested by Thomas (1990). In addition, a positive shift of delta13C in benthic foraminifers after the event indicates nutrient-depleted bottom water at Site 752.

Neogene benthic foraminifers from the Kerguelen Plateau

Benthic foraminifers were studied quantitatively in 120 lower Miocene through upper Pleistocene samples from Ocean Drilling Program Site 747 (Central Kerguelen Plateau) and Sites 748 and 751 (Southern Kerguelen Plateau). These sites are situated on an 450-km-long, north-south transect between 54°49'S and 58°26'S at present water depths between 1696 and 1288 m. Principal component analysis on the census data of the most abundant 92 taxa helped to identify 8 benthic foraminifer assemblages. These benthic foraminifer assemblages were compared with Holocene faunas from southern high latitudes to reconstruct paleoenvironmental conditions. Middle lower Miocene sediments are characterized by a Uvigerina hispidocostata assemblage, indicating high paleoproductivity and/or not well-ventilated bottom water. From late early to late middle Miocene time, the Southern Kerguelen Plateau was bathed by a young, well-oxygenated, and carbonate-aggressive water mass, as indicated by a Nuttallides umbonifer-dominated benthic foraminifer assemblage. During late middle Miocene time, an Astrononion pusillum assemblage took over for only about 1 m.y., probably indicating the first injection of an aged water mass, similar to the North Atlantic Deep Water (NADW), into a developing circumpolar current system. Around the middle to late Miocene boundary, the fauna again became dominated by N. umbonifer. After the last appearance of N. umbonifer, reestablishment of the A. pusillum assemblage from the early late through at least the late late Miocene, indicated the established influence of a NADW-like water mass. The latest Miocene through middle late Pliocene benthic foraminifer assemblage was characterized by Epistominella exigua and strong carbonate dissolution, indicating very high biosiliceous production, and this in turn may indicate the formation and paleoposition of an Antarctic Polar Frontal Zone. From the late late Pliocene, a Trifarina angulosa assemblage (indicative today of sandy substrate and vigorous bottom currents) strongly dominated the fauna up to the late Pleistocene, when Bulimina aculeata (indicative today of calm sedimentation with high organic matter fluxes) became an important and partly dominating constituent of the fauna. This is interpreted as the faunal response to the decreased winnowing force (bottom current velocities) of the Antarctic Circumpolar Current during periods of global climatic amelioration and raised sea level.

Cenozoic benthic foraminifers from ODP Leg 134 holes

This paper discusses the Paleobathymetric and paleoenvironmental history of the New Hebrides Island Arc and North d'Entrecasteaux Ridge during Cenozoic time based on benthic foraminiferal and sedimentological data. Oligocene and Pliocene to Pleistocene benthic foraminiferal assemblages from Sites 827, 828, 829, and 832 of Ocean Drilling Program (ODP) Leg 134 (Vanuatu) are examined by means of Q-mode factor analysis. The results of this analysis recognize the following bathymetrically significant benthic foraminiferal biofacies: (1) Globocassidulina subglobosa biofacies and Bulimina aculeata-Bolivinita quadrilatera biofacies representing the upper bathyal zone (600-1500 m); (2) Gavelinopsis praegeri-Cibicides wuellerstorfi biofacies, indicating the Pacific Intermediate Water (water depth between 1500 and 2400 m); (3) Tosaia hanzawai-Globocassidulina muloccensis biofacies, Valvulineria gunjii biofacies, and the Melonis barleeanus-Melonis sphaeroides biofacies, which characterize the lower bathyal zone; (4) the Nuttallides umbonifera biofacies, which characterizes the interval between the lysocline (approximately 3500 m) and the carbonate compensation depth (approximately 4500 m); and (5) the Rhabdammina abyssorum biofacies representing the abyssal zone below the carbonate compensation depth. Benthic foraminiferal patterns are used to construct Paleobathymetric and paleogeographic profiles of the New Hebrides Island Arc and North d'Entrecasteaux Ridge for the following age boundaries: late Miocene/Pliocene, early/late Pliocene, Pliocene/Pleistocene, and Pleistocene/Holocene.

Foraminifer faunas in the Tagus Prodelta

Pluri-annual proxy records of marine sediment cores from the Tagus Prodelta off Lisbon, Portugal, have been generated to gain insight into the climatic and hydrographic changes in the area during the twentieth century. The study includes benthic and planktonic foraminiferal faunas and the stable isotopic composition of one benthic (Uvigerina celtica) and two planktonic (Globigerina bulloides and Globorotalia inflata) foraminiferal species. Sea bottom and surface water temperatures were estimated based on the d18O values of these species and compared with instrumental data. The foraminiferal fauna and the isotope-based temperature record indicate increasing temperatures throughout the last century. The immigration of a new species, Saidovina karreriana, to the area around 100 years ago indicates changes in the trophic conditions and water mass properties, which are probably at least partly due to anthropogenic pollution.

Neogene benthic foraminiferal community and organic carbon at DSDP Holes 95-612 and 95-613

Quantitative study of benthic foraminifers from the upper Miocene to lower Pliocene section at Site 612 (1404 m present water depth) and the Pliocene section at Site 613 (2323 m present water depth) shows no evidence of widespread downslope transport of shallow-water biofacies or reworking of older material in the greater than 150 µm size fraction. In contrast, upper Miocene sediments from Site 604 (2364 m present water depth) show extensive reworking and downslope transport. At Site 612, benthic foraminifers show a succession from an upper Miocene Bolivina alata-Nonionella sp. biofacies, to an uppermost Miocene Bulimina alazanensis biofacies, to a lower Pliocene Cassidulina reflexa biofacies, to an upper Pliocene Melonis barleeanum-Islandiella laevigata biofacies. Evidence suggests that the Pliocene biofacies are in situ, although they could have been transported downslope from the upper-middle bathyal zone. At Site 613, Uvigerina peregrina dominated the "middle" Pliocene, while Globocassidulina subglobosa was dominant in the early and late Pliocene. High abundances of U. peregrina at Site 613 are associated with high values of sedimentary organic carbon.

Benthic foraminifers in Mesozoic and Cenozoic sediments of the southwestern Atlantic

Benthic foraminiferal assemblages in Mesozoic and Cenozoic sediments were studied at Sites 511, 512, 513, and 514 drilled during Leg 71 in the southwestern Atlantic on the Maurice Ewing Bank and in the Argentine Basin. Benthic foraminifers in almost all stratigraphic subdivisions of Sites 511 and 512 reflect the gradual subsidence of the Falkland Plateau from shelf depths in the Barremian-Albian, when a semiclosed basin with restricted circulation of water masses and anaerobic conditions existed, to lower bathyal depths in the Late Cretaceous and Cenozoic, with an abrupt acceleration at the boundary of Lower and Upper Cretaceous. The composition, distribution, and preservation of Late Cretaceous assemblages of benthic foraminifers suggest considerable fluctuations of the foraminiferal lysocline and the CCD. This is evidenced by dissolution facies and foraminiferal assemblages in which agglutinated and resistant calcareous forms predominated during high stands of the CCD and by calcareous facies in which rich assemblages of calcareous species predominated during low stands. The highest position of the CCD on the Plateau (less than 1500-2000 m) was in the late Cenomanian, Turonian, and Coniacian. In the Santonian and Campanian the CCD was at depths below 1500-2000 meters. At the end of the Campanian the CCD shifted again to depths comparable with those of Cenomanian and Turonian time. In the latest Campanian and the Maestrichtian the CCD was low and nanno-foraminiferal oozes with a rich assemblage of benthic foraminifers accumulated. Foraminiferal assemblages at Sites 513 and 514 in the Argentine Basin also testify to oceanic subsidence from lower bathyal depths in the Oligocene to abyssal ones at present. This process was complicated by the influence of geographical migrations of the Polar Front caused by extensions of the ice sheet in the Antarctic after the opening of the Drake Passage during the Oligocene. In Mesozoic and Cenozoic deposits of the Falkland Plateau and the Argentine Basin seven assemblages of benthic foraminifers were distinguished by age: early-middle Albian, middle-late Albian, Late Cretaceous (including four groups), middle Eocene, late Eocene-early Miocene, middle-late Miocene, and Pliocene-Quaternary. The Albian assemblages contain many species common to the foraminiferal fauna of the Austral Biogeographical Province. The Late Cretaceous assemblage contains, along with Austral species, species common to foraminifers of North America, Western Europe, the Russian platform, and the south of the U.S.S.R. Deep-sea cosmopolitan species prevail in Cenozoic assemblages.

Distribution of benthic foraminifera in surface sediments on the continental margin off North-West Africa

The benthic foraminiferal populations along three traverses across the Northwest African continental margin were analyzed on the base of ca. 60 surface sediment samples. Depth ranges of 213 species were established and the main trends of vertical distribution are compared with those known from adjacent regions. Main faunal breaks occure at 100/200 m and 1000/1500 m depth of water. Some species show latitudinal distribution boundaries and the same applies to population density (standing stock), reflecting the regional distribution of nutrients supply by river discharge and upwelling processes. - High proportions of Bolivina test at the lower slope indicate extended downslope transport.

Foraminifers from DSDP Leg 87 holes

Leg 87 investigated two sites in the Nankai Trough, off southeastern Japan, and one in the Japan Trench, off northeastern Japan. Several holes at the Nankai Trough sites penetrated mostly Quaternary interbedded sandy turbidites and hemipelagic mud. Foraminifers are common only in certain turbidite sands because both sites are at or just below the carbonate compensation depth. The planktonic assemblages from these sandy layers consist of mixed cool-temperate and warm-water species, and include both solution-resistant and solution-prone species. The benthic assemblages from these same layers are composed of mixtures of shelf to abyssal species. The northward-flowing Kuroshio is important in producing the mixed planktonic faunas, whereas turbidity currents are the primary agents in mixing benthic faunas and in the rapid burial of both planktonic and benthic foraminifers, which protects them from solution. Interbedded hemipelagic muds are barren or contain sparse faunas. Hole 582B penetrated through the trench-fill deposits into hemipelagic sediments that originated in the Shikoku Basin. These muds contain a dissolution facies of solution-resistant planktonic species, partially dissolved tests, and deep bathyal benthic species. Drilling at Site 584, on the landward midslope of the Japan Trench, penetrated a section of dominantly diatomaceous mudstone. This section contains a meager Pliocene calcareous fauna in its upper third and a nearly monospecific assemblage of Martinottiella communis in the lower two-thirds. Diatom biostratigraphy indicates that this change in assemblages occurs near the Miocene/Pliocene boundary. Similar biofacies changes are observed in neighboring sections drilled during Legs 56 and 57. The change from agglutinated to calcareous faunas is probably related to a relative drop in the carbonate compensation depth at the end of the Miocene.

Paleogene benthic foraminifera from the Kerguelen Plateau

Benthic foraminifers were studied from lower Paleocene through upper Oligocene sections from Sites 747 and 748. The composition of the benthic foraminifer species suggests a middle to lower bathyal (600-2000 m) paleodepth during the Neogene and a probable upper abyssal (2000-3000 m) paleodepth during the Paleocene at Site 747. Site 748 is thought to have remained at middle to lower bathyal paleodepths throughout the Cenozoic. Principal component analysis distinguished four major benthic foraminifer assemblages: (1) a Paleocene Stensioina beccariiformis assemblage at Sites 747 and 748, (2) an early Eocene Nuttallides truempyi assemblage at lower bathyal Site 747, (3) an early through middle Eocene Stilostomella-Lenticulina assemblage at middle bathyal Site 748, and (4) a latest Eocene through Oligocene Cibicidoides-Astrononion pusillum assemblage at both sites. Major benthic foraminifer changes, as indicated by the principal components and first and last appearances, occurred at or close to the Paleocene/Eocene boundary, and in the late Eocene close to the middle/late Eocene boundary.

Benthic foraminiferal response to the emergence of the Isthmus of Panama and coincident paleoceanographic changes

Late Cenozoic benthic foraminiferal faunas from the Caribbean Deep Sea Drilling Project (DSDP) Site 502 (3052 m) and East Pacific DSDP Site 503 (3572 m) were analyzed to interpret bottom-water masses and paleoceanographic changes occurring as the Isthmus of Panama emerged. Major changes during the past 7 Myr occur at 6.7-6.2, 3.4, 2.0, and 1.1 Ma in the Caribbean and 6.7-6.4, 4.0-3.2, 2.1, 1.4, and 0.7 Ma in the Pacific. Prior to 6.7 Ma, benthic foraminiferal faunas at both sites indicate the presence of Antarctic Bottom Water (AABW). After 6.7 Ma benthic foraminiferal faunas indicate a shift to warmer water masses: North Atlantic Deep Water (NADW) in the Caribbean and Pacific Deep Water (PDW) in the Pacific. Flow of NADW may have continued across the rising sill between the Caribbean and Pacific until 5.6 Ma when the Pacific benthic foraminiferal faunas suggest a decrease in bottom-water temperatures. After 5.6 Ma deep-water to intermediate-water flow across the sill appears to have stopped as the bottom-water masses on either side of the sill diverge. The second change recorded by benthic foraminiferal faunas occurs at 3.4 Ma in the Caribbean and 4.0-3.2 Ma in the Pacific. At this time the Caribbean is flooded with cold AABW, which is either gradually warmed or is replaced by Glacial Bottom Water (GBW) at 2.0 Ma and by NADW at 1.1 Ma. These changes are related to global climatic events and to the depth of the sill between the Caribbean and Atlantic rather than the rising Isthmus of Panama. Benthic foraminiferal faunas at East Pacific Site 503 indicate a gradual change from cold PDW to warmer PDW between 4.0 and 3.2 Ma. The PDW is replaced by the warmer, poorly oxygenated PIW at 2.1 Ma. Although the PDW affects the faunas during colder intervals between 1.4 and 0.7 Ma, the PIW remains the principal bottom-water mass in the Guatemala Basin of the East Pacific.

Oliogocene to Pleistocene benthic foraminifera in ODP Leg 121 sites

Oligocene to Pleistocene bathyal benthic foraminifers at Broken Ridge (Site 754) and Ninetyeast Ridge (Site 756), eastern Indian Ocean, were investigated for then- stratigraphic distribution and their response to paleoceanographic changes. Q-mode factor analysis was applied to relative abundance data of the most abundant benthic foraminifers. At Site 754, seven varimax assemblages were recognized from the upper Oligocene to the Pleistocene: the Gyroidina orbicularis-Rectuvigerina striata Assemblage in the uppermost Oligocene; the Lenticulina spp. Assemblage in the upper Oligocene to lower Miocene, and in lower Miocene to lowermost middle Miocene; the Burseolina cf. pacifica-Cibicidoides mundulus Assemblage in the lower Miocene; the Planulina wuellerstorfi Assemblage in the upper middle Miocene; the Globocassidulina spp. Assemblage in the upper Miocene; the Gavelinopsis lobatulus-Uvigerina proboscidea Assemblage in the Pliocene; and the Ehrenbergina spp. Assemblage in the Pleistocene. The major faunal changes are complex, but exist between the Lenticulina spp. Assemblage and the P. wuellerstorfi Assemblage at ~13.8 Ma, and between the Ehrenbergina spp. Assemblage and the G. lobatulus Assemblage at ~5 Ma. The development of the P. wuellerstorfi and Globocassidulina spp. Assemblages after 13.8 Ma is correlated with the decrease in temperature of the intermediate waters of the ocean, in turn related to Antarctic glacial expansion. The faunal changes at ~5 Ma are related to the development of low oxygen intermediate water, formed in the presence of a strong thermocline. At Site 756, six varimax assemblages are distributed as follows: the Cibicidoides cf. mundulus-Oridorsalis umbonatus Assemblage in the lower Oligocene; the Epistominella umbonifera-Cibicidoides mundulus Assemblage from the upper Oligocene to the lower Miocene; the Cibicidoides mundulus-Burseolinapacifica Assemblage from lower Miocene to the lower middle Miocene; the Globocassidulina spp. Assemblage from the upper lower Miocene to the Pliocene; the Uvigerina proboscidea Assemblage in the upper Miocene and the Pliocene; and the Globocassidulina sp. D Assemblage in the Pliocene. The main faunal change at this site is between the E. umbonifera Assemblage and the Globocassidulina spp. Assemblage, at ~17.1 Ma. The timing of this faunal change is coeval with faunal changes in the North Atlantic and the Pacific. The change is related to a change in bottom water characteristics caused by an increased influence of carbonate corrosive water from the Antarctic source region, and a change in surface productivity. A low oxygen event at Site 756, which started at about 7.3 Ma, occurred about 2.3 m.y. before that at Site 754. The different response to global paleoceanographic changes is not yet explained, but may be due to the difference of marine topography and the degree of upwelling

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.

Macrofauna abundance and sediment characteristics during R/V Senckenberg cruise west of Sylt in september 2010

The continuously influence of human impacts on the seafloor and benthic habitats demands the knowledge of clearly defined habitats to assess recent conditions and to monitor future changes. In this study, a benthic habitat dominated by sorted bedforms was mapped in 2010 using biological, sedimentological and acoustic data. This approach reveals the first interdisciplinary analysis of macrofauna communities in sorted bedforms in the German Bight. The study area covered 4 km², and was located ca. 3.5 km west of island of Sylt. Sorted bedforms formed as sinuous depressions with an east west orientation. Inside these depressions coarse sand covers the seafloor, while outside predominantly fine to medium sand was found. Based on the hydroacoustic data, two seafloor classes were identified. Acoustic class 1 was linked to coarse sand (type A) found inside these sorted bedforms, whereas acoustic class 2 was related to mainly fine to medium sands (type B). The two acoustic classes and sediment types corresponded with the macrofauna communities 1 and 2. The Aoinides paucibranchiata-Goniadella bobretzkii community on coarse sand and the Spiophanes bombyx - Magelona johnstonii community on fine sand. A transitional community 3 (Scoloplos armiger - Ophelia community), with species found in communities 1 and 2, could not be detected by hydroacoustic methods. This study showed the limits of the used acoustic methods, which were unable to detect insignificant differences in the fauna composition of sandy areas.

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.

Planktonic foraminifera in Core ML2_66, North Atlantic

Evolution of approaches and methods for reconstruction of paleoenvironmental conditions from microfossils contained in bottom sediments is assessed. Authors elaborated a new actualistic basis for such reconstructions, consisting of a database on contents of tests of planktonic foraminifers in the surface layer of Atlantic sediments and a package of mathematical tools for computer data processing. Structure of the database is described. It contains data on test contents for 29 species and varieties of planktonic foraminifers in 381 samples. A mathematical model designed for reconstructions is based on factor analysis and multidimensional spline interpolation. The model allows one to deduce Quaternary hydrological parameters (paleotemperature, paleosalinity) for standard hydrological levels down to depth of 250 m for the four seasons of the year. Reconstructions are illustrated by an example of a sedimentary core from the North Atlantic representing a period of 300 ky. During the next to last and the last maxima of continental glaciation (oxygen isotope stages 8, 6, 4, and 2), the subarctic water mass was spread here. Winter and summer surface water temperatures comprised 1-5° and 5-7°C, respectively. During interglacials and in Holocene the conditions were close to present ones: winter and summer surface water temperatures comprised 10-12 and 15-17°C, respectively. Vertical paleohydrological profiles compiled for peaks of climatostratigraphic intervals suggest that during cold intervals water stratification was stronger than during the warm ones. At depth 50 m seasonal salinity oscillations did not exceed 0.4 per mil and commonly salinity was minimum in winter and maximum in summer.