Showing papers on "Foraminifera published in 2003"

Benthic foraminifera (Protista) as tools in deep-water palaeoceanography: environmental influences on faunal characteristics.

Abstract: Foraminiferal research lies at the border between geology and biology. Benthic foraminifera are a major component of marine communities, highly sensitive to environmental influences, and the most abundant benthic organisms preserved in the deep-sea fossil record. These characteristics make them important tools for reconstructing ancient oceans. Much of the recent work concerns the search for palaeoceanographic proxies, particularly for the key parameters of surface primary productivity and bottom-water oxygenation. At small spatial scales, organic flux and pore-water oxygen profiles are believed to control the depths at which species live within the sediment (their 'microhabitats'). Epifaunal/shallow infaunal species require oxygen and labile food and prefer relatively oligotrophic settings. Some deep infaunal species can tolerate anoxia and are closely linked to redox fronts within the sediment; they consume more refractory organic matter, and flourish in relatively eutrophic environments. Food and oxygen availability are also key factors at large (i.e. regional) spatial scales. Organic flux to the sea floor, and its seasonality, strongly influences faunal densities, species compositions and diversity parameters. Species tend to be associated with higher or lower flux rates and the annual flux range of 2-3 g Corg m-2 appears to mark an important faunal boundary. The oxygen requirements of benthic foraminifera are not well understood. It has been proposed that species distributions reflect oxygen concentrations up to fairly high values (3 ml l-1 or more). Other evidence suggests that oxygen only begins to affect community parameters at concentrations < 0.5 ml l-1. Different species clearly have different thresholds, however, creating species successions along oxygen gradients. Other factors such as sediment type, hydrostatic pressure and attributes of bottom-water masses (particularly carbonate undersaturation and current flow) influence foraminiferal distributions, particularly on continental margins where strong seafloor environmental gradients exist. Epifaunal species living on elevated substrata are directly exposed to bottom-water masses and flourish where suspended food particles are advected by strong currents. Biological interactions, e.g. predation and competition, must also play a role, although this is poorly understood and difficult to quantify. Despite often clear qualitative links between environmental and faunal parameters, the development of quantitative foraminiferal proxies remains problematic. Many of these difficulties arise because species can tolerate a wide range of non-optimal conditions and do not exhibit simple relationships with particular parameters. Some progress has been made, however, in formulating proxies for organic fluxes and bottom-water oxygenation. Flux proxies are based on the Benthic Foraminiferal Accumulation Rate and multivariate analyses of species data. Oxygen proxies utilise the relative proportions of epifaunal (oxyphilic) and deep infaunal (low-oxygen tolerant) species. Yet many problems remain, particularly those concerning the calibration of proxies, the closely interwoven effects of oxygen and food availability, and the relationship between living assemblages and those preserved in the permanent sediment record.

Thermal evolution of Cretaceous Tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels

Abstract: [1] The evolution of subtropical (30–35°N) upper ocean temperatures through the Cretaceous is inferred from the oxygen isotope compositions of 64 fish teeth (enamel) coming from the western Tethyan platform Mean δ18O values of 22‰ at the Berriasian-Valanginian boundary decrease, with oscillations to 185‰ around the Cenomanian-Turonian boundary, and progressively increase to 215‰ by the end of the Cretaceous The similarity of this oxygen isotope curve for bioapatites from platform environments with those for foraminifera and bulk carbonates that were deposited in deeper waters and at other paleolatitudes indicates that they record global climatic signals Major cooling events at the million-year scale can be distinguished: (1) at the Berriasian-Valanginian boundary and (2) during the earliest Late Valanginian A third cooling event is detected during the earliest Aptian These events, already proposed as icehouse interludes during the lower Cretaceous, are also recorded at subtropical latitudes A progressive warming is identified from the Aptian to the Cenomanian-Turonian interval that corresponds to a thermal optimum, and then upper ocean temperatures decreased to the Maastrichtian Minimum isotopic temperatures range from 15°C to 28°C, assuming a δ18Oseawater of −1‰, for an ice-free world Taking more realistic δ18Oseawater values of ∼0‰ for tropical waters, during glacial periods (within the Berriasian-Valanginian interval, and earliest Aptian) or with above average salinities (possibly the Maastrichtian), temperatures are increased by 4–5°C Temperature differences between climatic extremes of the Valanginian and Cenomanian-Turonian are estimated to have been 10°C Latitudinal thermal gradients for the Albian-Cenomanian, Turonian, and Maastrichtian were 02–03°C/° latitude and thus weaker than modern oceanic values at about 04°C/° latitude

Carbonate Systems along Nutrient and Temperature Gradients: Some Sedimentological and Geochemical Constraints

Abstract: Research over the past several decades has clearly demonstrated that changes in the ocean environ- ment have had major impacts on carbonate systems. Changes in climate, ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry, including carbonate saturation state and nutri- ent availability, and thereby have determined boundary conditions for the biota that form carbonate platforms. In turn, the biota determine accumulation rates and facies zonations, thus controlling platform geometry and facies dynamics. In the first section of this paper, we examine how nutrient availability influences carbonate facies associations. We first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations. Then we discuss how carbonate sedimentation can be characterized along nutrient gradients. In the second section, we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems. We highlight the variety of existing proxies and their limitations, and suggest that multiple lines of evidence are needed for valid interpre- tations. Our short review discusses sedimentological, biogenic, and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleo- ceanographic controls over the distribution of carbonate associations. However, it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs. nutrient supplies changes and facies in ancient carbonate sequences.

Palaeo-oceanography: Deepwater variability in the Holocene epoch

Abstract: The conversion of surface water to deep water in the North Atlantic results in the release of heat from the ocean to the atmosphere, which may have amplified millennial-scale climate variability during glacial times1 and could even have contributed to the past 11,700 years of relatively mild climate (known as the Holocene epoch)2,3,4. Here we investigate changes in the carbon-isotope composition of benthic foraminifera throughout the Holocene and find that deep-water production varied on a centennial–millennial timescale. These variations may be linked to surface and atmospheric events that hint at a contribution to climate change over this period.

Seasonal and interannual variability of benthic foraminiferal faunas at 550 m depth in the Bay of Biscay

Abstract: Live benthic foraminiferal faunas were sampled 10 times between October 1997 and April 2000 at a 550 m depth open-slope station in the Bay of Biscay. Duplicate cores for 5 samplings allow distinguishing between spatial and temporal variability of the foraminiferal faunas. Although spatial patchiness of the foraminiferal faunas is substantial, especially in the 63–150 μm fraction, the temporal variability appears to be larger. The foraminiferal patterns are compared with surface water primary production as assessed by the study of available SeaWIFS satellite images. In the study area, the primary production regime is marked by a pulselike and prolonged spring bloom and possibly a short fall bloom. Such periods of elevated chlorophyll-a concentration are followed, after a delay of about 4–6 weeks, by a strong frequency increase of the most opportunistic taxa of benthic foraminifera. Surprisingly, no change of bottom and interstitial water oxygenation and of redox conditions within the sediment is recorded. The small taxa Epistominella exigua, Reophax guttiferus, Bolivina spathulata, Cassidulina carinata and Nuttallides pusillus appear to respond first to a labile organic matter input, by a reproductive event marked by a strong patchy spatial distribution hypothetically resulting of the spatial heterogeneity of organic matter deposits. Uvigerina peregrina and Uvigerina mediterranea, the most opportunistic larger taxa, strongly dominate the >150 μm fraction during eutrophic periods (spring and fall blooms). Intermediate and deep infaunal taxa seem to depend less on fresh organic matter input, even if a small frequency increases are recorded in the >150 μm fraction during the most productive periods; Globobulimina affinis and Melonis barleeanus show reproductive events in rather shallow sediment layers in the more oligotrophic periods of the year. A conceptual model explains the increasing delay in the response to important phytoplankton bloom periods for the successive benthic ecosystem compartments.

The evolution of early Foraminifera.

Abstract: Fossil Foraminifera appear in the Early Cambrian, at about the same time as the first skeletonized metazoans. However, due to the inadequate preservation of early unilocular (single-chambered) foraminiferal tests and difficulties in their identification, the evolution of early foraminifers is poorly understood. By using molecular data from a wide range of extant naked and testate unilocular species, we demonstrate that a large radiation of nonfossilized unilocular Foraminifera preceded the diversification of multilocular lineages during the Carboniferous. Within this radiation, similar test morphologies and wall types developed several times independently. Our findings indicate that the early Foraminifera were an important component of Neoproterozoic protistan community, whose ecological complexity was probably much higher than has been generally accepted.

Correlated terrestrial and marine evidence for global climate changes before mass extinction at the Cretaceous-Paleogene boundary.

Abstract: Terrestrial climates near the time of the end-Cretaceous mass extinction are poorly known, limiting understanding of environmentally driven changes in biodiversity that occurred before bolide impact. We estimate paleotemperatures for the last ≈1.1 million years of the Cretaceous (≈66.6–65.5 million years ago, Ma) by using fossil plants from North Dakota and employ paleomagnetic stratigraphy to correlate the results to foraminiferal paleoclimatic data from four middle- and high-latitude sites. Both plants and foraminifera indicate warming near 66.0 Ma, a warming peak from ≈65.8 to 65.6 Ma, and cooling near 65.6 Ma, suggesting that these were global climate shifts. The warming peak coincides with the immigration of a thermophilic flora, maximum plant diversity, and the poleward range expansion of thermophilic foraminifera. Plant data indicate the continuation of relatively cool temperatures across the Cretaceous–Paleogene boundary; there is no indication of a major warming immediately after the boundary as previously reported. Our temperature proxies correspond well with recent pCO2 data from paleosol carbonate, suggesting a coupling of pCO2 and temperature. To the extent that biodiversity is correlated with temperature, estimates of the severity of end-Cretaceous extinctions that are based on occurrence data from the warming peak are probably inflated, as we illustrate for North Dakota plants. However, our analysis of climate and facies considerations shows that the effects of bolide impact should be regarded as the most significant contributor to these plant extinctions.

A 23,000-Year Record of Surface Water pH and PCO2 in the Western Equatorial Pacific Ocean

Abstract: The oceans play a major role in defining atmospheric carbon dioxide (CO2) levels, and although the geographical distribution of CO2 uptake and release in the modern ocean is understood, little is known about past distributions. Boron isotope studies of planktonic foraminifera from the western equatorial Pacific show that this area was a strong source of CO2 to the atmosphere between approximately 13,800 and 15,600 years ago. This observation is most compatible with increased frequency of La Nina conditions during this interval. Hence, increased upwelling in the eastern equatorial Pacific may have played an important role in the rise in atmospheric CO2 during the last deglaciation.

Initiation of Northern Hemisphere glaciation and strengthening of the northeast Indian monsoon: Ocean Drilling Program Site 758, eastern equatorial Indian Ocean

Abstract: The Indian monsoon system, as recorded by ocean-floor biota (benthic foraminifera) at Ocean Drilling Program Site 758 in the eastern equatorial Indian Ocean, has varied dramatically over the past 5.5 m.y., long after the onset of the monsoons at 10‐8 Ma. Benthic foraminifera that thrive with high productivity year-round were common before the formation of Northern Hemisphere continental ice sheets ca. 3.1‐2.5 Ma, indicating that the summer (southwest) monsoon had high intensity and long seasonal duration. Ca. 2.8 Ma benthic faunas became dominated by taxa that flourish with a seasonally strongly fluctuating food supply, indicating that the northeast (winter) monsoon, during which primary productivity is relatively low, increased in duration and strength to form a system similar to that of today. The change occurred coeval with the initiation of the Northern Hemisphere glaciation, documenting a close link between the development of the Indian monsoon and Northern Hemisphere glaciation.

From greenhouse to icehouse : the marine Eocene-Oligocene transition

Abstract: Part I: The Pacific Rim Pacific Coast Eocene-Oligocene Marine Chronostratigraphy: A Review and an Update, by Donald R. ProtheroTurnovers in Marine Gastropod Faunas During the Eocene-Oligocene Transition, West Coast of the United States, by Richard L. SquiresBiotic Response to the Eocene-Oligocene Transition: Gastropod Assemblages in the High-Latitude North Pacific, by Anton E. Oleinik and Louie Marincovich Jr.Changes in Shallow-Marine Faunas from the Northeastern Pacific Margin Across the Eocene/Oligocene Boundary, by Elizabeth A. NesbittEvidence for Abrupt Eocene-Oligocene Molluscun Faunal Change in the Pacific Northwest, by Carole S. HickmanAn Overview of Eocene-Oligocene Echinoderm Faunas of the Pacific Northwest, by Casey Burns and Rich MooiUpper Eocene Greenhouse Deposits in Southern Australia: Paleoclimatology and Paleoceanography, by Paul R. Gammon, Yvonne Bone, Jonathan D.A. Clarke, and Noel P. JamesThe Meiji Drift Body and Late Paleogene-Neogene Paleoceanography of the North Pacific-Bering Sea Region, by David W. Scholl, Andrew J. Stevenson, Marlene A. Noble, and David K. ReaCetacean Evolution and Eocene-Oligocene Oceans Revisited, by R. Ewan FordyceTerrestrial Eocene-Oligocene Vegetation and Climate in the Pacific Northewest, by Jeffrey A. MyersPart II: The Atlantic, Gulf, and Caribbean Sequence Stratigraphy of the Eocene/Oligocene Boundary Interval: Southeastern Mississippi, by Ronald J. Echols, John M. Armentrout, Stephan A. Root, Larry B. Fearn, James C. Late Middle Eocene Glacioeustasy: Stable Isotopes and Foraminifera from the Gulf Coastal Plain, by John V. Hurley and Richard H. FluegemanPaleogene Temperature History of the U.S. Gulf Coastal Plain Inferred from -- of Fossil Otoliths, by Linda C. Ivany, Kyger C. Lohmann, and William P. PattersonThe Palynological Record of Late Eocene Climate Change, Northwest Gulf o Mexico, by Thomas E. Yancey, William C. Elsik, and Recep H. SancayPalynological Patterns in Uppermost Eocene to Lower Oligocene Sedimentary Rocks in the U.S. Gulf Coast, by Francisca E. Oboh-Ikuenobe and Carlos A. JaramilloLate Eocene-Early Oligocene Benthic Foraminifera in the Gulf Coastal Plain: Regional vs. Global Influences, by Richard H. FluegemanUpper Paleogene larger Foraminiferal Succession on a Tropical Carbonate Bank, Nicaragua Rise, Caribbean Region, by Edward RobinsonMolluscan Faunas Across the Eocene/Oligocene Boundary in the North American Gulf Coastal Plain, with Comparisons to Those of the Eocene and Oligocene of France, by David T. Dockery III and Pierre LozouetBiotic Patterns in Eocene-Oligocene Echinoids of the Southeastern United States, by Burchard D. CarterThe Eocene-Oligocene Transition in Marine Vertabrates of the Gulf Coastal Plain, by Earl M. ManningA Brief Account of the Evolution of the Caribbean Seaway: Jurassic to Present, by Manuel A. Iturralde VinentThe Eocene-Oligocene Transition in the Equatorial Atlantic (ODP Site 925): Paleoproductivity Increase and Positive -- Excursion, by Liselotte Diester-Haass and Jim ZachosPart III: The North Sea and Tethys The Eocene/Oligocene Boundary in the North Sea Area: A Sequence Stratigraphic Approach, by Noel Vandenberghe, Henk Brinkhuis, and Etinne SteurbautDeep-Water Benthic Foraminiferal Events from the Massignano Eocene/Oligocene Boundary Stratotype, Central Italy, by Rodolfo Coccioni and Simone GaleottiStratigraphy and Benthic Foraminiferal Events Across the Middle - Late Eocene Transition in Western Negev, Israel, by Roberto Barbieri, Chaim Benjamini, Simonetta Monechi, and Viviana RealeThe Development of Facies Patterns of Middle Eocene to Lower Oligocene Circum-Alpine, Shallow-Water Carbonate Environments, by James H. Nebelsick, Michael Rasser, and Davide BassiPart IV: Causes and Consequences Late Eocene Impacts: Geologic Record, Correlation, and Paleoenvironmental Consequences, by C. Wylie Poag, Edward Mankinen, and Richard D. NorrisBoundaries, Turnover, and the Causes of Evolutionary Change: A Perspective from the Cenozoic, by Warren D. AllmonThe Marine Eocene-Oligocene Transition: A Synthesis, by Linda C. Ivany, A. Nesbitt, and Donald R. ProtheroContributorsIndex

Selective feeding by benthic foraminifera on phytodetritus on the western Antarctic Peninsula shelf: evidence from fatty acid biomarker analysis

Abstract: This study presents the first direct evidence, based on biochemical analysis of fresh material, that certain benthic foraminifera feed selectively on specific components of seasonally deposited phytodetritus in their natural environment. Three abundant species of benthic foramini- fera, the calcareous species Globocassidulina subglobosa and Quinqueloculina seminula and the agglutinated species Thurammina albicans, collected after the deposition of phytoplankton bloom material at a shelf site (560 m water depth) west of the Antarctic Peninsula in March 2001, showed significant differences in their fatty acid profiles compared to the surrounding phytodetritus. Fur- thermore, the 2 calcareous species contained significantly higher amounts of polyunsaturated fatty acids (PUFAs) than were found in their presumptive phytodetrital food source, indicating that the foraminifera discriminate between, and selectively feed on, the different components of the deposited material. Possible implications for the benthic food web are discussed.

Is methane venting at the seafloor recorded by δ13C of benthic foraminifera shells

Abstract: The research was supported by WCNURP grant PF806880 and by NSF grants OCE-9731157, OCE-9815186, and OCE-9906944. Curation of sediment cores at the OSU/NORCOR repository is supported by NSF.

Relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in Monterey Bay, California

Abstract: [1] As part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release, we compared ambient pore water chemistry with the distribution and stable isotopic composition of living (rose Bengal stained) foraminifera in MBARI ROV Ventana tube cores taken from modern seepage areas (about 1000 m water depth) in Monterey Bay, California. Benthic foraminiferal isotopic differences between sites clearly indicate that methane-influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry. Carbon isotope signatures of living benthic foraminifera did not conform to the very negative (−30 to −48‰), methane-influenced carbon isotope values of the pore waters they live in. Instead, the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published δ13C values of foraminifera living in nonseep habitats. It is not clear what relative influences biological, ecological, and physical factors have on the carbon isotopic signatures observed in seep foraminifera. Substantial carbon isotope differences can exist between individuals of the same seep species. For instance, δ13C values of living Globobulimina pacifica varied by as much as 2.9‰ between seeps within 8 km of each other, whereas δ13C values of living Uvigerina peregrina varied by as much as 1.95‰ within the same seep. Provided there is no diagenetic alteration of the test carbonate, isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage.

Contrasting Deep-water Records from the Upper Permian and Lower Triassic of South Tibet and British Columbia: Evidence for a Diachronous Mass Extinction

Abstract: Remarkably different Late Permian–Early Triassic marine records are seen in sections from the western deep-water margin of Pangea (Ursula Creek, British Columbia) and the high paleolatitude, southern margin of the Neotethyan Ocean (Selong, South Tibet). The Ursula Creek section reveals the progressive decline of seafloor oxygen values in the Changxingian Stage (loss of bioturbation, authigenic U enrichment, appearance of pyrite framboid populations), followed by the persistent development of euxinic conditions in the latest Changxingian and throughout the Early Triassic; an event that coincides with the disappearance of a siliceous sponge fauna and the loss of diverse radiolarian populations. The Selong section, which was located on a distal passive margin, records regression and erosion in the mid-Changxingian, followed by a phase of deepening that began in the late Changxingian. The boundary interval is associated with a marked diversity increase due to the appearance of equatorial taxa (foraminifera, brachiopods, and sponges), suggesting warming without extinction in marine waters at high southern paleolatitudes. Only in the late Griesbachian Stage are the diverse Permian holdovers eliminated, again at a level showing evidence for dysoxia (thinly-bedded, authigenic U-enriched, pyrite-rich limestone). Thus, the end-Permian mass extinction is seen to be diachronous by half a million years or more, with late Changxingian extinction in Panathalassa coinciding with diversity increase associated the migration of warm-water taxa into the high southerly paleolatitudes regions of Neotethys.

Tropical sea-surface temperature reconstruction for the early Paleogene using Mg/Ca ratios of planktonic foraminifera

Abstract: [1] To understand the climate dynamics of hypothesized past greenhouse intervals, it is essential to constrain tropical sea-surface temperatures (SST), yet existing proxy records give conflicting results. Here we present the first Mg/Ca-based study of pre-Quaternary SST and investigate early Paleogene (late Paleocene through late middle Eocene; 58.6–39.8 Ma) tropical temperatures, using planktonic foraminifera belonging to the genus Morozovella from Ocean Drilling Program Site 865 on Allison Guyot (western central equatorial Pacific Ocean). Calcification temperatures similar to or warmer than modern tropical SST are calculated using a range of assumptions regarding diagenesis, temperature calibration, and seawater Mg/Ca. Long-term warming is observed into the early Eocene (54.8–49.0 Ma), with peak SST between 51 and 48 Ma and rapid cooling of 4°C beginning at 48 Ma. These findings are inconsistent with the δ18O-based SST previously estimated for this site.

A Budget of Carbonate Framework and Sediment Production, Kailua Bay, Oahu, Hawaii

Abstract: Sediments of the bay and coastal plain of Kailua (Oahu, Hawaii) are > 90% biogenic carbonate produced by destruction of primary reef framework (coral and encrusting coralline algae) and by direct sedimentation through the biological activity of calcifying organisms (the green alga Halimeda, the branching coralline alga Porolithion gardineri, molluscs, and benthic foraminifera). Field measurements of benthic community structure, gross carbonate production, bioerosion, and direct sedimentation in 17 physiographic zones in Kailua Bay are used to calculate modern calcareous sediment production rates in the 12 km2 fringing reef system. Total gross carbonate productivity by corals and encrusting coralline algae (based on mapped percent cover and known growth rates) occurs at an average rate of 1.22 (± 0.36) kg m-2 y-1 over hard substrates of the reef platform, corresponding to 0.8 (± 0.2) mm y-1 (using a bulk density of 1.48 g cm-3, the average of coral and coralline algae). Coralline algae contributes 42% of the total gross productivity. Bioerosion of coral and coralline algae facies at and near the reef surface (estimated from slabbed reef samples) occurs at average rates of 0.10-1.15 kg m-2 y-1 and releases 1,911 (± 436) m3 of unconsolidated carbonate sediment annually. Mechanical erosion (coral breakage) likely contributes an additional 315 m3 y-1. Carbonate sediment is also produced directly by the green alga Halimeda, branching coralline algae, molluscs, and benthic foraminifera at a combined rate of 1,822 (± 200) m3 y-1 (using densities specific to sediment origin). The total rate of production of unconsolidated carbonate sediment in Kailua Bay is the sum of these sources, amounting to 4,048 (± 635) m3 y-1. Normalizing gross sediment production (in kg y-1) by reef habitat area (in m2) generates average rates of productivity (in kg m-2 y-1) that are directly comparable to each other and to the literature; such rates can also be employed and tested in other reef settings. In Kailua Bay, the total production of calcareous sediment corresponds to an average (normalized) rate of 0.53 (± 0.19) kg m-2 y-1, with 0.33 (± 0.13) kg m-2 y-1 contributed through erosion of the coralgal framework and 0.20 (± 0.06) kg m-2 y-1 contributed by direct sediment production on the reef surface. Applying these modern sediment-production rates over the 5,000 years that Kailua Bay has been completely inundated by postglacial sea-level rise, an estimated 20.2 (± 3.2) 106 m3 of unconsolidated carbonate sediment has been produced in the system. The volume of sediment stored in the various reef channels and holes in Kailua Bay is 3.7 (± 0.3) 106 m3, or 19% of that produced since 5,000 y BP. The volume of sand in the modern beach is 1.0 (± 0.1) 106 m3, or 5% of Holocene sediment production. The volume of carbonate sediment stored in the coastal plain is estimated, using core-log data and associated radiocarbon ages, to be 10.0 (± 1.8) 106 m3, or 51% of Holocene sediment production. The remaining 25% likely represents sediment loss due to the natural processes of dissolution, attrition, and transport offshore. These export terms are not well understood and emphasize the need for sediment dynamics to be incorporated into reef and sediment budgets. Although sediment production in this reef system is prodigious, the rate of "new" sediment supplied to the beachface is less than 2% of what moves on and off the beach seasonally.

Early Cenozoic benthic foraminiferal isotopes: Species reliability and interspecies correction factors

Abstract: [1] Oxygen and carbon isotope records are important tools used to reconstruct past ocean and climate conditions, with those of benthic foraminifera providing information on the deep oceans. Reconstructions are complicatedby interspecies isotopic offsets that result from microhabitat preferences (carbonate precipitation in isotopically distinct environments) and vital effects (species-specific metabolic variation in isotopic fractionation). We provide correction factors for early Cenozoic benthic foraminifera commonly used for isotopic measurements (Cibicidoides spp., Nuttallides truempyi, Oridorsalis spp., Stensioina beccariiformis, Hanzawaia ammophila, and Bulimina spp.), showing that most yield reliable isotopic proxies of environmental change. The statistical methods and larger data sets used in this study provide more robust correction factors than do previous studies. Interspecies isotopic offsets appear to have changed through the Cenozoic, either (1) as a result of evolutionary changes or (2) as an artifact of different statistical methods and data set sizes used to determine the offsets in different studies. Regardless of the reason, the assumption that isotopic offsets have remained constant through the Cenozoic has introduced an ∼1 -2°C uncertainty into deep sea paleotemperature calculations. In addition, we compare multiple species isotopic data from a western North Atlantic section that includes the Paleocene-Eocene thermal maximum to determine the most reliable isotopic indicator for this event. We propose that Oridorsalis spp. was the most reliable deepwater isotopic recorder at this location because it was best able to withstand the harsh water conditions that existed at this time; it may be the best recorder at other locations and for other extreme events also.

A common opportunistic foraminiferal species as an indicator of rapidly changing conditions in a range of environments

Abstract: Long-term biological and environmental time-series (several decades to centuries) are essential for distinguishing between anthropogenically and naturally induced environmental change as well as for monitoring environmental change over time, irrespective of the causes. Since such long time-series are virtually non-existent for most areas, other methods have to be explored which can provide the best possible analogues. Numerous investigations have shown that benthic foraminifera (meiofaunal protists), which leave a fossil record in most marine sediments, are well suited for this purpose. A prerequisite for performing sound interpretations is an optimal understanding of their biology and ecology. Stainforthia fusiformis (Williamson) is one of the most common benthic foraminiferal species in NW European waters and living (stained) populations have been recorded in all clastic, soft bottom intertidal to outer shelf and slope areas with sediments consisting of at least some fines (>4% 28. Its predominance in ephemerally dysoxic/anoxic areas has caused it to be used as a proxy for severe oxygen depletion. A strong dominance (even >90%) of this species is, however, also reported from well-oxygenated coastal and shelf settings and, consequently, high abundance of this species occurs in habitats with very different environmental characteristics. A closer examination of these areas suggests that they can be roughly grouped into three categories: (1) beneath hydrographic frontal areas, (2) physically disturbed areas of sediment, and (3) ephemerally dysoxic/anoxic basins. The main characteristic feature that these highly different environments have in common is that they experience rapidly changing conditions. It is concluded that the opportunistic life-strategy of S. fusiformis makes it highly adapted to cope with environmental stress and that this, rather than tolerance to a particular environmental parameter, causes it to predominate in areas subject to rapidly changing environmental conditions.

Illustration of modern benthic foraminifera frombermuda and remarks on distribution in other subtropical/tropical areas

Abstract: A scanning light microscope (SLM) is used to illustrate recent benthic foraminiferal species from surface sediment samples collected in Bermuda subtropical environments. Species illustrated here are the main foraminiferal species found in Bermuda lagoons, reefs, caves, mangroves, and ponds, but also occur in most subtropical and tropical areas. The SLM permits photography of specimens without coating and gives pictures most similar to specimens that micropaleontologists see under a dissecting reflected light microscope in a petri dish with water, in contrast to images made with scanning electron microscopes. These pictures are the first SLM illustrations of subtropical/tropical species of benthic foraminifera and will be very useful for their identification. Bermuda recent sediment hosts a benthic foraminifera fauna as diverse as in other subtropical and tropical areas, and the general trends of foraminiferal distribution and morphology are similar. Remarks on foraminiferal distribution in Bermuda and other subtropical/tropical areas are also presented.

Foraminifera as Proxies for Sea-Level Change on Siliciclastic Margins

Abstract: oxygen minimum zone dynamic coastal and shelf fronts thermocline tidal mixing runoff high energy turbidity daily–seasonal fluctuations in temperature & salinity ± high productivity halocline shelf break