Showing papers on "Foraminifera published in 1999"

Use of proxies in paleoceanography : examples from the South Atlantic

Abstract: Clues to Ocean History: a Brief Overview of Proxies.- Surface Water Circulation.- Sea-Surface Temperature Estimations Using a Modern Analog Technique with Foraminiferal Assemblages from Western Atlantic Quaternary Sediments.- The Distribution of Living Planktic Foraminifera in Relation to Southeast Atlantic Oceanography.- Coccolithophores as Indicators of Ocean Water Masses, Surface-Water Temperature, and Paleoproductivity - Examples from the South Atlantic.- Calcareous Dinoflagellate Cysts as Paleo-Environmental Tools.- Oxygen Isotope Values of Planktic Foraminifera: A Tool for the Reconstruction of Surface Water Stratification.- Stable Isotopes of Pteropod Shells as Recorders of Sub-Surface Water Conditions: Comparison to the Record of G. ruber and to Measured Values.- On the Reconstruction of Paleosalinities.- Bottom- and Deep Water Circulation.- Stable Carbon Isotopes in Benthic Foraminifera: Proxies for Deep and Bottom Water Circulation and New Production.- Carbonate Dissolution in the Deep-Sea: Methods, Quantification and Paleoceanographic Application.- Kaolinite and Chlorite as Tracers of Modern and Late Quaternary Deep Water Circulation in the South Atlantic and the Adjoining Southern Ocean.- Paleoproductivity and Nutrients.- Organic Carbon and Carbonate as Paleoproductivity Proxies: Examples from High and Low Productivity Areas of the Tropical Atlantic.- Biogenic Barium as a Proxy for Paleoproductivity: Methods and Limitations of Application.- Variability in Export Production Documented by Downward Fluxes and Species Composition of Marine Planktic Diatoms: Observations from the Tropical and Equatorial Atlantic.- Reliability of the 231Pa/230 Th Activity Ratio as a Tracer for Bioproductivity of the Ocean.- Sediment Redistribution, 230Thex - Normalization and Implications for the Reconstruction of Particle Flux and Export Paleoproductivity.- The South Atlantic Carbon Isotope Record of Planktic Foraminifera.- Reconstruction of Surface Ocean Nitrate Utilization Using Stable Nitrogen Isotopes in Sinking Particles and Sediments.- CO2 in Oceans and Atmosphere.- Alkenone ?13C as a Proxy for Past PCO2 in Surface Waters: Results from the Late Quaternary Angola Current.- Reassessing Foraminiferal Stable Isotope Geochemistry: Impact of the Oceanic Carbonate System (Experimental Results).- Implications of a Carbonate Ion Effect on Shell Carbon and Oxygen Isotopes for Glacial Ocean Conditions.- Atmospherical Circulation.- Pollen and Spores in Marine Sediments from the East Atlantic - A View from the Ocean into the African Continent.- Terrestrial Organic Matter in Marine Sediments: Analytical Approaches and Eolian-Marine Records in the Central Equatorial Atlantic.- Environmental Magnetism.- The Magnetic View on the Marine Paleoenvironment: Parameters, Techniques, and Potentials of Rock Magnetic Studies as a Key to Paleoclimatic and Paleoceanographic Changes.- Using Rock Magnetic Proxy Records for Orbital Tuning and Extended Time Series Analyses into the Super- and Sub-Milankovitch Bands.- Geomagnetic Events and Relative Paleointensity Records - Clues to High-Resolution Paleomagnetic Chronostratigraphies of Late Quaternary Marine Sediments?.- Modelling.- Simulation of Oxygen Isotopes in a Global Ocean Model.- Reconstructing and Modelling the Last Glacial Maximum: Beyond CLIMAP.- Data Management.- Data Management of Proxy Parameters with PANGAEA.

Miocene evolution of atmospheric carbon dioxide

Abstract: Changes in pCO2 or ocean circulation are generally invoked to explain warm early Miocene climates and a rapid East Antarctic ice sheet (EAIS) expansion in the middle Miocene. This study reconstructs late Oligocene to late Miocene pCO2 from ep values based on carbon isotopic analyses of diunsaturated alkenones and planktonic foraminifera from Deep Sea Drilling Project sites 588 and 608 and Ocean Drilling Program site 730. Our results indicate that highest pCO2 occurred during the latest Oligocene (∼350 ppmv) but decreased rapidly at ∼25 Ma. The early and middle Miocene was characterized by low pCO2 (260–190 ppmv). Lower intervals of pCO2 correspond to inferred organic carbon burial events and glacial episodes with the lowest concentrations occurring during the middle Miocene. There is no evidence for either high pCO2 during the late early Miocene climatic optimum or a sharp pCO2 decrease associated with EAIS growth. Paradoxically, pCO2 increased following EAIS growth and obtained preindustrial levels by ∼10 Ma. Although we emphasize an oceanographic control on Miocene climate, low pCO2 could have primed the climate system to respond sensitively to changes in heat and vapor transport.

Foraminifera of oxygen-depleted environments

Abstract: In summary, certain benthic Foraminifera from various water depths inhabit oxygen-poor and even anoxic environments. It is established that at least some foraminiferal species survive anoxia and even sulfidic conditions for periods up to a few weeks, but the tolerance of most species to oxygen depletion is unknown. Furthermore, the physiological mechanisms enabling foraminiferal species to survive exposure to anoxia and/or sulfidic conditions are not yet identified. The available data suggest, however, that all Foraminifera are aerobic for at least part of their life, and, in all likelihood, some species are facultative anaerobes. Obligate anaerobes have not been identified among foraminiferal species. The information necessary to understand the diverse aspects of foraminiferal adaptation to oxygen-depleted environments must come from experimental studies. Only with such biological information, it will be possible to construct more accurate databases for use in other disciplines such as paleoecology and paleoceanography.

Atlas of Paleocene planktonic foraminifera

Abstract: Olsson, Richard K., Christoph Hemleben, William A. Berggren, and Brian T. Huber, editors. Atlas of Paleocene Planktonic Foraminifera. Smithsonian Contributions to Paleobiology, number 85, 252 pages, 37 figures, 71 plates, 1999.—Sixty-seven species of Paleocene planktonic foraminifera are described and illustrated, including three species of Eoglobigerina, four species of Parasubbotina, five species of Subbotina, two species of Hedbergella, 10 species oiGlobanomalina, six species ofAcarinina, 12 species of Morozovella, three species of lgorina, four species of Praemurica, one species of Guembelitria, one species of Globoconusa, three species of Parvularugoglobigerina, two species of Woodringina, six species of Chiloguembelina, one species of Rectoguembelina, and four species of Zeauvigerina. Taxonomic classification of normal perforate taxa are organized according to wall texture. Spinose cancellate genera include Eoglobigerina, Parasubbotina, and Subbotina; cancellate nonspinose genera include Igorinina and Praemurica; smooth-walled genera include Hedbergella and Globanomalina; and muricate genera include Acarinina and Morozovella. Taxonomic classification of microperforate taxa (including Guembelitria, Globoconusa, Parvularugoglobigerina, Woodringina, Chiloguembelina, Rectoguembelina, and Zeauvigerina) are organized according to test morphology. Scanning electron microscope (SEM) images of type species described by Morozova in the collections of the Geological Institute, Academy of Sciences (GAN), Moscow, and the type material described by Subbotina in the collections of the All Union Petroleum Scientific Research Geological Prospecting Institute (VNIGRI), St. Petersburg, are shown on Plates 8-12. Twelve species described by Morozova, nine species described by Subbotina, and one species described by Bykova are illustrated. In addition, SEM images of 28 holotypes and two paratypes from the Smithsonian Institution collections are shown on Plates 13-17, and the lectotype for Globigerina compressa Plummer, 1926, and the neotype for Globorotalia monmouthensis Olsson, 1961, are designated and illustrated with SEM images. Paleobiogeographic maps showing the global distribution of 29 commonly occurring Paleocene taxa are included in the atlas, as well as figures showing the stratigraphic ranges of species by genus and stratigraphic first and last appearances. The biostratigraphic framework used in the atlas is the revised biostratigraphy given in Berggren et al., 1995, which is summarized in the atlas. Wall texture and morphological relationships between species and genera form the basis of phylogenetic interpretations. This is discussed in the section "Wall Texture, Classification, and Phylogeny" and is referenced to Plates 1-7. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Annals of the Smithsonian Institution. SERIES COVER DESIGN: The trilobite Phacops rana Green. Library of Congress Cataloging-in-Publication Data Atlas of Paleocene planktonic foraminifera / Richard K. Olsson ... [et al.], editors. p. cm. — (Smithsonian contributions to paleobiology ; no. 85) Includes bibliographic references and index. 1. Foraminifera, Fossil. 2. Paleontology—Paleocene. I. Olsson, Richard K. II. Series. QE701.S56no.85 [QE772] 560s-dc21 [561'.994] 98-3474 ® The paper used in this publication meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library Materials Z39.48—1984.

Benthic foraminiferal microhabitats below the sediment-water interface

Abstract: Benthic Foraminifera do not live exclusively at the sediment-water interface, and can be found alive at considerable depths in marine sediments, in many cases down to 10 cm ( Fig. 10.1) . Within this depth interval, large changes take place in the natural environment, especially in the case of finegrained sediments, the surface layer and the deep sediment layers forming two very different worlds. At the sediment-water interface, the sea water may be rich (even saturated) in oxygen, high-quality organic matter is often available, and in the photic zone, there is l ight. Deep in the sediment, conditions are drastically different: often there is no oxygen, except in halos around metazoan burrows, but there may be toxic substances (e.g. instead. Furthermore, the remaining organic matter may be mostly refractory, with a low nutritional value (see chapter 11) . Apparently, the deeper sediment layers, with their poverty of resources and lack of oxygen, form an inhospitable or even hostile environment for many organisms, and as a consequence, animal life is generally scarce (Fenchel and Finlay, 1995). Nevertheless,

Symbiont-bearing Foraminifera

Abstract: Of approximately 150 extant families of Foraminifera, less than 10% harbor algal endosymbionts (Lee and Anderson, 1991a). Nevertheless, these families are responsible for much of the carbonate produced by the Foraminifera, because symbiosis is prevalent in tropical larger foraminifers and planktonic foraminifers, the two groups that are the most prolific carbonate producers. Globally, Milliman and Droxler (1995) estimated carbonate production at 5.7 billion tons per year, of which larger foraminifers produce about 0.5% and planktonic foraminifers produce about 20% (Langer, 1997). Lee and Anderson (199 l a ) , in their review of the biology of symbiosis in Foraminifera, listed four miliolid, three rotaliid, and five globigerinid families as hosts of algal symbionts belonging to three divisions and five classes of the algae. A few members of several families of smaller rotaliid foraminifers (e.g. Asterigerinidae) appear to host endosymbionts, but those relationships await study. In addition, members of several families are able to sequester chloroplasts, which are harvested from algal food, for days to weeks after ingestion (Lopez, 1979; Cedhagen, 1991; Lee and Anderson, 1991a). While this is not a true symbiosis, chloroplast sequestering does enable these protists to benefit directly from photosynthesis. Algal symbiosis appears to have arisen independently in most of these lineages of Foraminifera, as well as in several now extinct lineages. Evidence for independent origins is strongest for the miliolid families and subfamilies. The ornamented Peneroplidae (Fig. 8.1.A) host symbionts belonging to the red algae (Division Rhodophyta) (Fig. 8.2.A), while the unornamented Peneroplidae (Fig. 8.1.B) and the Archaiasinae (Family Soritidae) (Fig. 8.1.C) host symbionts belonging to the green algae (Division Chlorophyta) (Fig. 8.2B). The Soritinae (Family Soritidae) (Fig. 8.1.D) host dinoflagellate symbionts (Division Chromophyta, Class Pyrrophyceae) (Fig. 8.2.C), and the Alveolinidae I Fig. 8.1.E) host diatom symbionts (Division Chromophyta, Class Bacillariophyceae). Among the planktonic Foraminifera (Fig. 8.3), both dinoflagellate (Fig. 8.2.D) and chrysophyte (Division Chromophyta, Class Chrysophyceae) (Fig. 8.2.E) symbionts are common. Recent isotopic studies (Norris, 1996a) indicate that within

The record of global change in mid-Cretaceous (Barremian-Albian) sections from the Sierra Madre, Northeastern Mexico

Abstract: Our current understanding of mid-Cretaceous global change is largely based on investigations of pelagic sections from southern Europe and deep sea drilling sites. Much less information exists from other continents and from hemipelagic sections deposited on continental margins. This investigation seeks to broaden our understanding of mid-Cretaceous global change by focusing on the record from hemipelagic sections deposited along the continental margin of northeastern Mexico. The major goals are to compare the record, timing, and extent of the Oceanic Anoxic Events (OAEs) in Mexico and other areas, and to determine the relationship between these events and the global burial of organic material using carbon isotopes. We have investigated four sections from the Sierra Madre Oriental, integrating biostratigraphy, magnetostratigraphy and carbon isotope stratigraphy. Carbon isotopes, measured on the organic carbon (C org ) fraction, show identical stratigraphic changes to curves from Barremian to lower Albian European and Pacific deep-sea sections. Our results add new detail to the C-isotope stratigraphy of the middle and late Albian interval. Three abrupt peaks in C org content correlate with OAE1a (early Aptian), OAE1b (early Albian) and an event in the late Aptian Globigerinelloides algerianus Zone. All three events are marked by short-term, 0.5-3 per mil decreases in C-isotope values followed by increases of similar magnitude. The decreases may reflect changes in the type of C org , the nature of carbon cycling, or an increase in hydrothermal activity. The increases in C-isotope values reflect widespread burial of C org . The similar shape of the C-isotope curves in Mexico and other areas, and the response of C-isotopes to the OAEs, indicate that the late Aptian episode was extensive, and that OAE1a and OAE1b were global. The three anoxic events appear to correlate with rising relative sea level. OAE1a also corresponds to major changes in nannofossil assemblages; the well-known "nannoconid crisis" can be easily recognized in the Mexican sections. This event is characterized by an increase in abundance of nannofossils and foraminifera in sediments, possibly reflecting a decrease in dilution as a result of the rise in relative sea level.

Clues to Ocean History: a Brief Overview of Proxies

Abstract: The reconstruction of ocean history employs a large variety of methods with origins in the biological, chemical, and physical sciences, and uses modern statistical techniques for the interpretation of extensive and complex data sets. Various sediment properties deliver useful information for reconstructing environmental parameters. Those properties that have a close relationship to environmental parameters are called “proxy variables” (“proxies” for short). Proxies are measurable descriptors for desired (but unobservable) variables. Surface water temperature is probably the most important parameter for describing the conditions of past oceans and is crucial for climate modelling. Proxies for temperature are: abundance of microfossils dwelling in surface waters, oxygen isotope composition of planktic foraminifera, the ratio of magnesium or strontium to calcium in calcareous shells or the ratio of certain organic molecules (e.g. alkenones produced by coccolithophorids). Surface water salinity, which is important in modelling of ocean circulation, is much more difficult to reconstruct. At present there is no established method for a direct determination of this parameter. Measurements associated with the paleochemistry of bottom waters to reconstruct bottom water age and flow are made on benthic foraminifera, ostracodes, and deep-sea corals. Important geochemical tracers are δ13C and Cd/Ca ratios. When using benthic foraminifera, knowledge of the sediment depth habitat of species is crucial. Reconstructions of productivity patterns are of great interest because of important links to current patterns, mixing of water masses, wind, the global carbon cycle, and biogeography. Productivity is reflected in the flux of carbon into the sediment. There are a number of fluxes other than those of organic carbon that can be useful in assessing productivity fluctuations. Among others, carbonate and opal flux have been used, as well as particulate barite. Furthermore, microfossil assemblages contain clues to the intensity of production as some species occur preferentially in high-productivity regions while others avoid these. One marker for the fertility of sub-surface waters (that is, nutrient availability) is the carbon isotope ratio within that water (I3C/12C, expressed as δ13C). Carbon isotope ratios in today’s ocean are negatively correlated with nitrate and phosphate contents. Another tracer of phosphate content in ocean waters is the Cd/Ca ratio. The correlation between this ratio and phosphate concentrations is quite well documented. A rather new development to obtain clues on ocean fertility (nitrate utilization) is the analysis of the 15N/14N ratio in organic matter. The fractionation dynamics are analogous to those of carbon isotopes. These various ratios are captured within the organisms growing within the tagged water. A number of reconstructions of the partial pressure of CO2 have been attempted using δ13C differences between planktic and benthic foraminifera and δ13C values of bulk organic material or individual organic components. To define the carbon system in sea water, two elements of the system have to be known in addition to temperature. These can be any combination of total CO2, alkalinity, or pH. To reconstruct pH, the boron isotope composition of carbonates has been used. Ba patterns have been used to infer the distribution of alkalinity in past oceans. Information relating to atmospheric circulation and climate is transported to the ocean by wind or rivers, in the form of minerals or as plant and animal remains. The most useful tracers in this respect are silt-sized particles and pollen.

Direct effects of CO2 concentration on growth and isotopic composition of marine plankton

Abstract: The assessment of direct effects of anthropogenic CO 2 increase on the marine biota has received relatively little attention compared to the intense research on CO 2 -related responses of the terrestrial biosphere. Yet, due to the rapid air–sea gas exchange, the observed past and predicted future rise in atmospheric CO 2 causes a corresponding increase in seawater CO 2 concentrations, [CO 2 ], in upper ocean waters. Increasing [CO 2 ] leads to considerable changes in the surface ocean carbonate system, resulting in decreases in pH and the carbonate concentration, [CO 2 −3 ]. These changes can be shown to have strong impacts on the marine biota. Here we will distinguish between CO 2 -related responses of the marine biota which (a) potentially affect the ocean's biological carbon pumps and (b) are relevant to the interpretation of diagnostic tools (proxies) used to assess climate change on geological times scales. With regard to the former, three direct effects of increasing [CO 2 ] on marine plankton have been recognized: enhanced phytoplankton growth rate, changing elemental composition of primary produced organic matter, and reduced biogenic calcification. Although quantitative estimates of their impacts on the oceanic carbon cycle are not yet feasible, all three effects increase the ocean's capacity to take up and store atmospheric CO 2 and hence, can serve as negative feedbacks to anthropogenic CO 2 increase. With respect to proxies used in palaeo-reconstructions, CO 2 -sensitivity is found in carbon isotope fractionation by phytoplankton and foraminifera. While CO 2 - dependent isotope fractionation by phytoplankton may be of potential use in reconstructing surface ocean p CO 2 at ancient times, CO 2 -related effects on the isotopic composition of foraminiferal shells confounds the use of the difference in isotopic signals between planktonic and benthic shells as a measure for the strength of marine primary production. The latter effect also offers an alternative explanation for the large negative swings in δ 13 C of foraminiferal calcite between glacial and interglacial periods. Changes in [CO 2 −3 ] affect the δ 18 O in foraminiferal shells. Taking this into account brings sea surface temperature estimates for the glacial tropics closer to those obtained from other geochemical proxies. DOI: 10.1034/j.1600-0889.1999.00023.x

Foraminifera in marginal marine environments

Abstract: Hundreds of known benthic foraminifer species live in coastal marine environments. Most of them are rare. The dominant species are widely distributed, many across major biogeographic barriers. The transoceanic distribution of some abundant marsh and estuarine species is hard to explain, except by accidental transport and high tolerance to environmental variables. The transition from a brackish to a normal-marine nearshore fauna is generally marked by increases in species diversity and the proportion of calcareous species in the community. A few calcareous genera are represented by the same or sibling species on the soft, clastic substrates of many inner continental shelves, spanning large latitudinal and longitudinal ranges. Hard substrates and marine vegetation in the tropics support a large variety of taxa, including nearly all living species of larger Foraminifera. With a few exceptions, the biogeographic imprint on nearshore, open-marine faunas is best seen in the composition of the entire assemblage, rather than in the presence or absence of a few dominant species.

Forward modeling of carbonate proxy data from planktonic foraminifera using oxygen isotope tracers in a global ocean model

Abstract: The distribution and variation of oxygen isotopes in seawater are calculated using the Goddard Institute for Space Studies global ocean model. Simple ecological models are used to estimate the planktonic foraminiferal abundance as a function of depth, column temperature, season, light intensity, and density stratification. These models are combined to forward model isotopic signals recorded in calcareous ocean sediment. The sensitivity of the results to the changes in foraminiferal ecology, secondary calcification, and dissolution are also examined. Simulated present-day isotopic values for ecology relevant for multiple species compare well with core-top data. Hindcasts of sea surface temperature and salinity are made from time series of the modeled carbonate isotope values as the model climate changes. Paleoclimatic inferences from these carbonate isotope records are strongly affected by erroneous assumptions concerning the covariations of temperature, salinity, and delta (sup 18)O(sub w). Habitat-imposed biases are less important, although errors due to temperature-dependent abundances can be significant.

Benthic Foraminifera and the flux of organic carbon to the seabed

Abstract: Organic carbon supply is a fundamental aspect of all biological communities, and the organic carbon flux is generally limited for marine benthic organisms. Benthic organisms shrouded in darkness, at water depths greater than a few tens of meters, are entirely dependent on imported organic carbon for their energy requirements. As we will show in this review, areal variations in the flux of organic carbon to the seafloor have a pervasive effect on the benthic community, including the Foraminifera. Because the processes and ecology are so different, we will examine separately the marine environments within and below the euphotic zone. Our review will be presented in four sections. The first will examine the production of organic matter in the marine realm and its delivery to the ocean floor. The second will summarize observations concerning Foraminifera and food supply. The third will review our basic understanding of the benthic response to organic carbon flux, and present ideas on and models of the response of benthic Foraminifera to that flux. These models will be examined using data concerning foraminiferal microecology, spatial distributions, morphology and abundances. The last section will survey the state of our knowledge and raise important questions which limit our understanding of benthic Foraminifera and their geologic record.

Paleoceanographic reconstructions from planktonic foraminifera off the Iberian Margin: Temperature, salinity, and Heinrich events

Abstract: A quantitative analysis of planktonic foraminifera in a core from the Iberian Margin allows a reconstruction of the evolution of oceanographic parameters during the last glacial cycle with a resolution of ∼1000 years. A principal component analysis performed on 19 species allows the identification of 11 intervals characterized by increased abundances of the subpolar species. The youngest six of these intervals are correlated with the last 6 Heinrich events (HEs). The five cold events older than stage 4 are dated at 81, 90, 110, 129, and 140 ka, respectively. Paleotemperatures reconstructed using the modern analog technique indicate 4°C decreases during all even-numbered isotopic stages and stage 3. During the HEs, temperature decreases reach ∼10°C and seawater δ18O anomalies reach ∼1‰. Temperature and salinity reconstructions indicate that the environment of the Iberian Margin has been under the combined influence of global factors such as the migration of the polar front and iceberg discharge and of regional factors such as the precipitation/evaporation regime on both oceanic and continental area.

Carbonate Dissolution in the Deep-Sea: Methods, Quantification and Paleoceanographic Application

Abstract: Understanding spatial and temporal changes in oceanic carbonate dissolution and preservation patterns is of key importance for testing models which seek to explain past changes in atmospheric pCO2 and surface water PCO2 through changes in the global carbon cycle. As part of the South Atlantic Dissolution Experiment, three deep-sea transects covering areas above and below the calcite lysocline into the Brazil and through the Cape Basin were investigated. Our work includes (1) determination of sediment surface assemblages of coccolithophores and planktic foraminifera; (2) SEM ultrastructure analysis of the planktic foraminifera Globigerina bulloides; and (3) comparative assessment of different carbonate dissolution proxies. We find that all dissolution proxies are able to distinguish the area above the calcite lysocline from the area below. Moreover, some parameters are qualified to distinguish the upper continental margin of upwelling areas from the open ocean. Regarding three different oceanographic regimes, only the carbonate ion content and the percentage of sediment carbonate content put us in the position to determine the total scale of the calcite transition zone. If these parameters are not available, a combination of the Globigerina bulloides Dissolution Index, the Calcidiscus leptoporus — Emiliania huxleyi Dissolution Index, and the rain ratio give the best approach to the authentic conditions.