Live benthic foraminifera in surface sediments of the Indo-Pakistan continental margin

The Indo-Pakistan Continental Margin represents an extreme habitat for benthic foraminifera since (1) high fluxes of organic matter offer a high food supply, (2) an intensified oxygen minimum Zone (OMZ) develops from the base of the euphotic Zone to water depths over 1000 m and (3) the monsoon causes seasonal oscillations within the biogeochemical cycle. At three stations from the uppermost (233 m), the central (658 m) and the deeper part (902 m) of the OMZ, living benthic foraminiferal assemblages were analyzed within the uppermost 10 cm of the sediment column. The ecologic structure of foraminiferal faunas is characterized by high abundances at the sediment surface and a rapid decrease within the uppermost 2 cm of the sediment column. Despite dysoxic to suboxic bottom-water conditions, stained benthic foraminifera occurred in all cores down to the base of the sampled interval. High surface abundances, a high dominance by few endobenthic calcareous taxa and a low diversity, which may result from specific physiological adaptations to almost anoxic conditions and the absence of predators, are recognized in the central part of the OMZ. The upper and lower margins of the OMZ are characterized by higher diversities and lower abundances. The shallowest part of the OMZ is dominated by calcareous foraminifera, whereas agglutinated species are the most common taxa in the deeper part. Comparisons with previous studies show that benthic foraminiferal assemblages, that are influenced by seasonal oscillations controlling food supply and/or the availability of oxygen, show variations in faunal density and species composition. Since there is strong evidence that oxygen is not a limiting factor for some taxa, it seems more likely that the distribution pattern of benthic foraminifera is preferentially controlled by trophic conditions.

Distribution of biological, anthropogenic, and volcanic constituents in the San Francisco Bay Coastal System

Although conventional sediment parameters (mean grain size, sorting, and skewness) and provenance have typically been used to infer sediment transport pathways, most freshwater, brackish, and marine environments are also characterized by abundant sediment constituents of biological, and possibly anthropogenic and volcanic, origin that can provide additional insight into local sedimentary processes. The biota will be spatially distributed according to its response to environmental parameters such as water temperature, salinity, dissolved oxygen, organic carbon content, grain size, and intensity of currents and tidal flow, whereas the presence of anthropogenic and volcanic constituents will reflect proximity to source areas and whether they are fluvially- or aerially-transported. Because each of these constituents have a unique environmental signature, they are a more precise proxy for that source area than the conventional sedimentary process indicators. This San Francisco Bay Coastal System study demonstrates that by applying a multi-proxy approach, the primary sites of sediment transport can be identified. Many of these sites are far from where the constituents originated, showing that sediment transport is widespread in the region. Although not often used, identifying and interpreting the distribution of naturally-occurring and allochthonous biologic, anthropogenic, and volcanic sediment constituents is a powerful tool to aid in the investigation of sediment transport pathways in other coastal systems.

Stable Isotope composition of particulate organic matter and fauna in a deep Mediterranean cold-water coral bank

Cold-water corals (CWC) are frequently reported from deep sites with locally accelerated currents that enhance seabed food particle supply. Moreover, zooplankton likely account for ecologically important prey items, but their contribution to CWC diet remains unquantified. We investigated the benthic food web structure of the recently discovered Santa Maria di Leuca (SML) CWC province (300 to 1100 m depth) located in the oligotrophic northern Ionian Sea. We analyzed stable isotopes (delta13C and delta15N) of the main consumers (including ubiquitous CWC species) exhibiting different feeding strategies, zooplankton, suspended particulate organic matter (POM) and sedimented organic matter (SOM). Zooplankton and POM were collected 3 m above the coral colonies in order to assess their relative contributions to CWC diet. The delta15N of the scleractinians Desmophyllum dianthus, Madrepora oculata and Lophelia pertusa and the gorgonian Paramuricea cf. macrospinawere consistent with a diet mainly composed of zooplankton. The antipatharian Leiopathes glaberrima was more 15N- depletedthan other cnidarians, suggesting a lower contribution of zooplankton to its diet. Our delta13C data clearly indicate that the benthic food web of SML is exclusively fuelled by carbon of phytoplanktonic origin. Nevertheless, consumers feeding at the water sediment interface were more 13C-enriched than consumers feeding above the bottom (i.e. living corals and their epifauna). This pattern suggests that carbon is assimilated via 2 trophic pathways: relatively fresh phytoplanktonic production for 13C-depleted consumers and more decayed organic matter for 13C-enriched consumers. When the delta13C values of consumers were corrected for the influence of lipids (which are significantly 13C-depleted relative to other tissue components), our conclusions remained unchanged, except in the case of L. glaberrima which could assimilate a mixture of zooplankton and resuspended decayed organic matter.

Iberian Margin 420 kyr geochemical and color variations record

Here we report 420 kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from these cores. Iberian Margin sediments contain strong precession power. Sediment "redness" (a* and 570-560 nm) and the ratio of long-chain alcohols to n-alkanes (C26OH/(C26OH + C29)) are highly coherent and in-phase with precession. Redder layers and more oxidizing conditions (low alcohol ratio) occur near precession minima (summer insolation maxima). We suggest these proxies respond rapidly to low-latitude insolation forcing by wind-driven processes (e.g., dust transport, upwelling, precipitation). Most Iberian Margin sediment parameters lag obliquity maxima by 7-8 ka, indicating a consistent linear response to insolation forcing at obliquity frequencies driven mainly by high-latitude processes. Although the lengths of the time series are short (420 ka) for detecting 100 kyr eccentricity cycles, the phase relationships support those obtained by Shackleton []. Antarctic temperature and the Iberian Margin alcohol ratios (C26OH/(C26OH + C29)) lead eccentricity maxima by 6 kyr, with lower ratios (increased oxygenation) occurring at eccentricity maxima. CO2, CH4, and Iberian SST are nearly in phase with eccentricity, and minimum ice volume (as inferred from Pacific d18Oseawater) lags eccentricity maxima by 10 kyr. The phase relationships derived in this study continue to support a potential role of the Earth's carbon cycle in contributing to the 100 kyr cycle.

Aprubt climate change events in the Northeastern Atlantic Ocean

The western Iberian margin has been one of the key locations to study abrupt glacial climate change and associated interhemispheric linkages. The regional variability in the response to those events is being studied by combining a multitude of published and new records. Looking at the trend from Marine Isotope Stage (MIS) 10 to 2, the planktic foraminifer data, conform with the alkenone record of Martrat et al. [2007], shows that abrupt climate change events, especially the Heinrich events, became more frequent and their impacts in general stronger during the last glacial cycle. However, there were two older periods with strong impacts on the Atlantic meridional overturning circulation (AMOC): the Heinrich-type event associated with Termination (T) IV and the one occurring during MIS 8 (269 to 265 ka). During the Heinrich stadials of the last glacial cycle, the polar front reached the northern Iberian margin (ca. 41°N), while the arctic front was located in the vicinity of 39°N. During all the glacial periods studied, there existed a boundary at the latter latitude, either the arctic front during extreme cold events or the subarctic front during less strong coolings or warmer glacials. Along with these fronts sea surface temperatures (SST) increased southward by about 1°C per one degree of latitude leading to steep temperature gradients in the eastern North Atlantic and pointing to a close vicinity between subpolar and subtropical waters. The southern Iberian margin was always bathed by subtropical water masses - surface and/ or subsurface ones -, but there were periods when these waters also penetrated northward to 40.6°N. Glacial hydrographic conditions were similar during MIS 2 and 4, but much different during MIS 6. MIS 6 was a warmer glacial with the polar front being located further to the north allowing the subtropical surface and subsurface waters to reach at minimum as far north as 40.6°N and resulting in relative stable conditions on the southern margin. In the vertical structure, the Greenland-type climate oscillations during the last glacial cycle were recorded down to 2465 m during the Heinrich stadials, i.e. slightly deeper than in the western basin. This deeper boundary is related to the admixing of Mediterranean Outflow Water, which also explains the better ventilation of the intermediate-depth water column on the Iberian margin. This compilation revealed that latitudinal, longitudinal and vertical gradients existed in the waters along the Iberian margin, i.e. in a relative restricted area, but sufficient paleo-data exists now to validate regional climate models for abrupt climate change events in the northeastern North Atlantic Ocean.

Planktonic foraminiferal stratigraphy and datum levels of ODP Leg 182 sites

Planktonic foraminifers from Ocean Drilling Program Leg 182, Holes 1126B and 1126C, 1128B and 1128C, 1130A and 1130B, 1132B, and 1134A and 1134B confirm the neritic record that during the early Miocene the Great Australian Bight region was in a cool-temperate regime with abundant Globoturborotalita woodi. Warm marine environments started to develop in the later part of the early Miocene, and the region became warm temperate to subtropical in the early middle Miocene with abundant Globigerinoides, Orbulina, and Globorotalia, corresponding to global warming at the Miocene climatic optimum. Fluctuations between cool- and warm-temperate conditions prevailed during the late Miocene, as indicated by abundant Globoconella conoidea and Menardella spp. A major change in planktonic foraminiferal assemblages close to the Miocene/Pliocene boundary not only drove many Miocene species into extinction but also brought about such new species as Globorotalia crassaformis and Globoconella puncticulata. Warm-temperate environments continued into the early and mid-Pliocene before being replaced by cooler conditions, supporting numerous Globoconella inflata and Globigerina quinqueloba. Based on data from this study and published results from the Australia-New Zealand region, we established a local planktonic foraminifer zonation scheme for separating the southern Australian Neogene (SAN) into Zones SAN1 to SAN19 characterizing the Miocene and Zones SAN20 to SAN25 characterizing the Pliocene. The Neogene sections from the Great Australian Bight are bounded by hiatuses of ~0.5 to >3 m.y. in duration, although poor core recovery in some holes obscured a proper biostratigraphic resolution. A total of 15 hiatuses, numbered 1 to 15, were identified as synchronous events from the base of the Miocene to the lower part of the Pleistocene. We believe that these are local manifestations of major third-order boundaries at about (1) 23.8, (2) 22.3, (3) 20.5, (4) 18.7, (5) 16.4, (6) 14.8, (7) 13.5, (8) 11.5, (9) 9.3, (10) 7.0, (11) 6.0, (12) 4.5, (13) 3.5, (14) 2.5, and (15) 1.5 Ma, respectively. This hiatus-bounded Neogene succession samples regional transgressions and stages of southern Australia and reveals its stepwise evolutionary history.

Component analysis of three TV-guided grab sampler from the Sahul Shelf (NW Australia)

This paper constitutes a first detailed and systematic facies and biota description of an isolated carbonate knoll (Pee Shoal) in the Timor Sea (Sahul Shelf, NW Australia). The steep and flat-topped knoll is characterized by a distinct facies zonation comprising (A) soft sediments with scattered debris and scarce sponges, hydrozoans and crinoids (320-210 m water depth), (B) hardground outcrops (step-like banks, vertical cliffs) that are mainly colonized by octocorals and sponges (210-75 m), and (C) the summit region (75-21 m) where the slopes merge gently into the flat-topped summit that is densely colonized by massive and encrusting zooxanthellate corals and the octocoral Heliopora coerulea. In contrast, the sediments recovered from the summit are dominated by the green alga Halimeda, subordinate components are corals, benthic foraminifers, mollusks, and coralline red algae. Thus, the sediments are classified as chlorozoan grain assemblage. However, non-skeletal grains (fecal pellets, ooids) are almost completely absent. This discrepancy between the living biota and the sediment composition could reflect a disruption by the severe tropical cyclone Ingrid that hit the northern Australian shelf in March 2005, just before the sampling for this study took place (September 2005).

Foraminifer, epifauna and infauna abundance of ODP Hole 183-1138A and core ELT54.007-PC, Kerguelen Plateau

Late Campanian and Maastrichtian benthic foraminifers are recorded from 12 samples from Ocean Drilling Program (ODP) Leg 183, Cores 183-1138A-52R through 63R (487.3-602.4 meters below seafloor), Kerguelen Plateau, Indian Ocean, and Danian benthics from one sample in the same section. The entire late Maastrichtian foraminifer fauna is noted from a dredge sample 220 km to the north. The structure of the fauna is compared with the Cenomanian-Turonian of the nearby Eltanin core E54-7. Faunas are reviewed in terms of planktonic percentage, composition, epifaunal/infaunal ratios, and dominance/diversity indices. The region was in the cool Austral Faunal Province through the Campanian-Maastrichtian and was probably warmer in the Cenomanian-Turonian. The ODP section is now 1600 meters below sea level and has subsided several hundred meters since deposition. Its fauna is dominated by epifaunal species suggesting little influence of upwelling. The dredge location has subsided little. Its fauna has a high infaunal content consistent with significant influence of upwelling near the plateau edge. The dominant benthic species remain constant through the ODP Cretaceous section, but subdominance changes, and the section is divided into three informal zones based on dominance/subdominance characteristics of the benthic fauna. Brief taxonomic comments are made on several species and some are figured.

Radiocarbon measurements and loose-sediment quantification of seafloor sediment samples off northern Mauritania

Heterozoan carbonates are typical for extratropical sedimentary systems. However, under mesotrophic to eutrophic conditions, heterozoan carbonates also form in tropical settings. Nevertheless, such heterozoan tropical sedimentary systems are rare in the modern world and therefore are only poorly understood to date. Here a carbonate depositional system is presented where nutrient-rich upwelling waters push onto a wide shelf. These waters warm up in the shelf, giving rise to the production and deposition of tropical heterozoan facies. The carbonate facies on this shelf are characterized by a mixture of tropical and cosmopolitan biogenic sedimentary grains. Study of facies and taxonomy are the key for identifying and characterizing tropical heterozoan carbonates and for distinguishing them from their coolwater counterparts, in particular in the past where the oceanography cannot be determined directly.

Benthic foraminifera in Tertiary sediments of DSDP Leg 90 holes

Eocene through Pliocene benthic foraminifers were examined from seven sites located at middle and lower bathyal depths on the Lord Howe Rise in the Tasman Sea, from another site at lower bathyal depths in the Coral Sea, and from a site in the intermediate-depth, hemipelagic province of the Chatham Rise, east of southern New Zealand. Age-related, depth-related, and bioprovincial faunal variations are documented in this chapter. One new species, Rectuvigerina tasmana, is named. The paleoecologic indications of several key groups, including the miliolids, uvigerinids, nuttallitids, and cibicidids, are combined with sedimentologic and stable isotopic tracers to interpret paleoceanographic changes in the Tasman Sea. Because the total stratigraphic ranges of many bathyal benthic foraminifers are not yet known, most endpoints in the Tasman Sea are considered ecologically controlled events. The disappearances of Uvigerina rippensis and Cibicidoidesparki and the first appearances of U. pigmaea, Sphaeroidina bulloides, and Rotaliatina sulcigera at the Eocene/Oligocene boundary can be considered evolutionary events, as also can the first appearance of Cibicides wuellerstorfi in Zone NN5. Species which are restricted to the lower bathyal zone except during discrete pulses, most of which are related to the development of glacial conditions, include Melonis pompilioides, M. sphaeroides, Pullenia quinqueloba, Nuttallides umbonifera, and U. hispido-costata. Middle bathyal indigenes include U. spinulosa, U. gemmaeformis, Ehrenbergina marwicki, R. sulcigera, and all rectuvigerinids except Rectuvigerina spinea. Although the miliolids first occurred at lower bathyal depths, they were more common in the middle bathyal zone. Although the Neogene hispido-costate uvigerinids first developed at lower bathyal depths and at higher middle latitude sites, in the later Neogene this group migrated to shallower depths and became predominant also in the middle bathyal zone. Despite the relatively similar sedimentologic settings at the six middle bathyal Tasman sites, there was extensive intrageneric and intraspecific geographic variation. Mililiolids, strongly ornamented brizalinids, bolivinitids, Bulimina aculeata, Osangularia culter, and strongly porous morphotypes were more common at higher latitudes. Osangularia bengalensis, striate brizalinids such as Brizalina subaenariensis, Gaudryina solida, osangularids in general, and finely porous morphotypes were more common in the subtropics. There was strong covariance between faunas at lower middle latitude, lower bathyal Site 591, and higher middle latitude, middle bathyal Site 593. The following oceanographic history of the Tasman Sea is proposed; using the stable isotopic record as evidence for glacials and examining the ecologic correlations between (1) miliolids and carbonate saturation, (2) nuttallitids and undersaturated, cooled, or "new" water masses, (3) uvigerinids with high organic carbon in the sediment and high rates of sediment accumulation, and (4) cibicidids and terrestrial organic carbon. The glacial located near the Eocene/Oligocene boundary is characterized by the penetration of cooler, more corrosive waters at intermediate depths in high southern latitudes. This may have caused overturn, upwelling pulses, in other Tasman areas. The development of Neogenelike conditions began in the late Oligocene (Zone NP24/NP25) with the evolution of several common Neogene species. A large number of Paleogene benthics disappeared gradually through the course of the early Miocene, which was not well preserved at any Tasman site. Corrosive conditions shallowed into the middle bathyal zone in several pulses during the early Miocene. The development of glacial conditions in the middle Miocene was accompanied by major changes throughout the Tasman Sea. Sediment accumulation rates increased and high-productivity faunas and corrosive conditions developed at all but the lowest-latitude Site 588. This increase in productivity and accumulation rate is attributed to the eutrophication of Antarctic water masses feeding Tasman current systems, as well as to invigorated circulation in general. It overlaps with the beginning of the Pacific High-productivity Episode (10-5 Ma). During the latest Miocene glacial episode, corrosive conditions developed at lower bathyal depths, while cooler water and lower nutrient levels shallowed to middle bathyal depths. Lower input of terrestrial organic carbon may be related to the lower nutrient levels of this time and to the termination of the Pacific High-productivity Episode. The moderate glacial episode during the mid-Pliocene (Zone NN15/NN16, ~3.2 Ma) corresponds to a decline in sediment accumulation rates and a reorganization of faunas unlike that of all other times. New genera proliferate and indices for cool, noncorrosive conditions and high organic carbon expand throughout the middle bathyal zone coeval with the sedimentation rate decreases. By the latest Pliocene (about 2.5 Ma), however, during another glacial episode, faunal patterns typical of this and later glacials develop throughout the Tasman Sea. Benthic foraminiferal patterns suggest increased input of terrestrial organic matter to Tasman Sea sediments during this episode and during later glacials.

Microfossil, stable isotope, and facies of a near-continuous core from the Gippsland Basin

Fossil, facies, and isotope analyses of an early high-paleolatitude (55°S) section suggests a highly unstable East Antarctic Ice Sheet from 32 to 27 Myr. The waxing and waning of this ice sheet from 140% to 40% of its present volume caused sea level changes of ±25 m (ranging from -30 to +50 m) related to periodic glacial (100,000 to 200,000 years) and shorter interglacial events. The near-field Gippsland sea level (GSL) curve shares many similarities to the far-field New Jersey sea level (NJSL) estimates. However, there are possible resolution errors due to biochronology, taphonomy, and paleodepth estimates and the relative lack of lowstand deposits (in NJSL) that prevent detailed correlations with GSL. Nevertheless, the lateral variations in sea level between the GSL section and NJSL record that suggest ocean siphoning and antisiphoning may have propagated synchronous yet variable sea levels.

Sediment geochemistry, foraminiferal fauna parameter, census counts and Varimax PC-factor loadings and scores of foraminiferal assemblages of sediment core GeoB12615-4

Analogous to West- and North Africa, East Africa experienced more humid conditions between approximately 12 to 5 kyr BP, relative to today. While timing and extension of wet phases in the North and West are well constrained, this is not the case for the East African Humid Period. Here we present a record of benthic foraminiferal assemblages and sediment elemental compositions of a sediment core from the East African continental slope, in order to provide insight into the regional shallow Indian Ocean paleoceanography and East African climate history of the last 40 kyr. During glacial times, the dominance of a benthic foraminiferal assemblage characterized by Bulimina aculeata, suggests enhanced surface productivity and sustained flux of organic carbon to the sea floor. During Heinrich Stadial 1 (H1), the Nuttallides rugosus Assemblage indicates oligotrophic bottom water conditions and therefore implies a stronger flow of southern-sourced AAIW to the study site. During the East African Humid Period, the Saidovina karreriana Assemblage in combination with sedimentary C/N and Fe/Ca ratios suggest higher river runoff to the Indian Ocean, and hence more humid conditions in East Africa. Between 8.5 and 8.1 kyr, contemporaneous to the globally documented 8.2 kyr Event, a severe reduction in river deposits implies more arid conditions on the continent. Comparison of our marine data with terrestrial studies suggests that additional moisture from the Atlantic Ocean, delivered by an eastward migration of the Congo Air Boundary during that time period, could have contributed to East African rainfall. Since approximately 9 kyr, the gaining influence of the Millettiana millettii Assemblage indicates a redevelopment of the East African fringe reefs.

Radiocarbon dating on cold-water corals, grain size, Corg, and benthic foraminfera assemblage of two sediment cores from the Ionian Sea

Continuous sedimentary records from an eastern Mediterranean cold-water coral ecosystem thriving in intermediate water depths (~600 m) reveal a temporary extinction of cold-water corals during the Early to Mid Holocene from 11.4-5.9 cal kyr BP. Benthic foraminiferal assemblage analysis shows low-oxygen conditions of 2 ml l**-1 during the same period, compared to bottom-water oxygen values of 4-5 ml l**-1 before and after the coral-free interval. The timing of the corals' demise coincides with the sapropel S1 event, during which the deep eastern Mediterranean basin turned anoxic. Our results show that during the sapropel S1 event low oxygen conditions extended to the rather shallow depths of our study site in the Ionian Sea and caused the cold-water corals temporary extinction. This first evidence for the sensitivity of cold-water corals to low oceanic oxygen contents suggests that the projected expansion of tropical oxygen minimum zones resulting from global change will threaten cold-water coral ecosystems in low latitudes in the same way that ocean acidification will do in the higher latitudes.

Distribution of benthic foraminifers in surface layer of bottom sediments from the littoral zone of the Kunashir Island, South Kuriles

Composition and abundance of modern benthic foraminifers in the littoral zone of the Kunashir Island (South Kuriles) were studied. This littoral zone was examined on the sides of the Sea of Okhotsk, the Pacific Ocean, and the Izmena Bay. In the littoral zone of the Izmena Bay benthic foraminifers were not found. The highest biodiversity and maximal density of foraminifers were observed at a bench among rocks and blocks, in depressions of various size and depth (baths), at places where algae and water plants were attached, on silty sands, and on sands with admixture of broken shells, silt, and clastic matter composing the coast. The lowest density and biodiversity were found in mouths of creeks and rivers, on rock plates free from sediments and attached algae and water plants, as well as in places not protected from wind and wave activity. It was established that on both sides of the Sea of Okhotsk and of the Pacific Ocean foraminiferal complexes vary both in biodiversity and in density of their distribution in the littoral zone.