Showing papers on "Foraminifera published in 2012"

Evolution of middle to Late Cretaceous oceans—A 55 m.y. record of Earth's temperature and carbon cycle

Abstract: A new 55 m.y. global compilation of benthic foraminifera δ 13 C and δ 18 O for the middle to Late Cretaceous shows that there was widespread formation of bottom waters with temperatures >20 °C during the Cretaceous greenhouse world. These bottom waters filled the silled North Atlantic and probably originated as thermocline or intermediate waters in the tropical oceans. Carbon burial during the Cretaceous oceanic anoxic events produced a positive δ 13 C shift in global carbon reservoirs, but this is not particularly large, especially by comparison with the remarkable Late Paleocene carbon maximum. The interbasin δ 13 C gradient was unusually large during the Cretaceous hot greenhouse, probably because the North Atlantic sills prevented the free exchange of waters in the deep basin. The hot greenhouse ended when the Equatorial Atlantic Gateway opened sufficiently to flood the deep North Atlantic with relatively cool polar waters formed in the Southern Ocean.

A taxonomic guide to modern benthic shelf foraminifera of the western Mediterranean Sea

Abstract: A total of 288 modern benthic carbonate shelf foraminifera in three areas of the Western Mediterranean Sea (Alboran Platform, Oran Bight and the southwest shelf of Mallorca) have been studied and are systematically listed. This systematic description provides a list of synonyms, short remarks about morphological features of the taxa and some annotations about taxa with problematic generic status. Most of the taxa are illustrated by SEM photographs. Yvonne Milker. Geological-Paleontological Institute and Museum (GPI u. M.), University of Hamburg, Bundesstrasse 55, 22307 Hamburg. Present address: Department of Geosciences, University of Tuebingen, Hoelderlinstrasse 12, 20146 Tuebingen. Yvonne.Milker@uni-tuebingen.de Gerhard Schmiedl. Geological-Paleontological Institute and Museum (GPI u. M.), University of Hamburg, Bundesstrasse 55, 20146 Hamburg. Gerhard.Schmiedl@uni-hamburg.de

End-Cretaceous marine mass extinction not caused by productivity collapse

Abstract: An asteroid impact at the end of the Cretaceous caused mass extinction, but extinction mechanisms are not well-understood. The collapse of sea surface to sea floor carbon isotope gradients has been interpreted as reflecting a global collapse of primary productivity (Strangelove Ocean) or export productivity (Living Ocean), which caused mass extinction higher in the marine food chain. Phytoplankton-dependent benthic foraminifera on the deep-sea floor, however, did not suffer significant extinction, suggesting that export productivity persisted at a level sufficient to support their populations. We compare benthic foraminiferal records with benthic and bulk stable carbon isotope records from the Pacific, Southeast Atlantic, and Southern Oceans. We conclude that end-Cretaceous decrease in export productivity was moderate, regional, and insufficient to explain marine mass extinction. A transient episode of surface ocean acidification may have been the main cause of extinction of calcifying plankton and ammonites, and recovery of productivity may have been as fast in the oceans as on land.

Oxygen isotopes in foraminifera: Overview and historical review

Abstract: —Foraminiferal tests are a common component of many marine sediments. The oxygen isotope ratio (δ 18 O) of test calcite is frequently used to reconstruct aspects of their life environment. The δ 18 O depends mainly on the isotope ratio of the water it is precipitated from, the temperature of calcification, and, to a lesser extent, the carbonate ion concentration. Foraminifera and other organisms can potentially preserve their original isotope ratio for many millions of years, although diagenetic processes can alter the ratios. Work on oxygen isotope ratios of foraminifera was instrumental in the discovery of the orbital theory of the ice ages and continues to be widely used in the study of rapid climate change. Compilations of deep sea benthic foraminifer oxygen isotopes have revealed the long history of global climate change over the past 100 million years. Planktonic foraminifer oxygen isotopes are used to investigate the history of past sea surface temperatures, revealing the extent of past 'greenhouse' warming and global sea surface temperatures.

Biostratigraphic and Geological Significance of Planktonic Foraminifera

Abstract: The role of fossil planktonic foraminifera as markers for biostratigraphical zonation and correlation underpins most drilling of marine sedimentary sequences and is key to hydrocarbon exploration. Biostratigraphic and Geological Significance of Planktonic Foraminifera unifies existing biostratigraphic schemes and provides an improved correlation reflecting regional biogeographies. It presents a comprehensive analysis of existing data on fossil planktonic foraminifera genera and their phylogenetic evolution in time and space. Coverage includes presentation and discussion of rarely studied thin sections of planktonic foraminifera, allowing for new developments in dating planktonic foraminifera in carbonates and expanding their usefulness in hydrocarbon exploration.

Benthic Foraminiferal Biogeography: Controls on Global Distribution Patterns in Deep-Water Settings

Abstract: Benthic foraminifera, shell-bearing protists, are familiar from geological studies. Although many species are well known, undescribed single-chambered forms are common in the deep sea. Coastal and sublittoral species often have restricted distributions, but wide ranges are more frequent among deep-water species, particularly at abyssal depths. This probably reflects the transport of tiny propagules by currents across ocean basins that present few insurmountable barriers to dispersal, combined with slow rates of evolution. Undersampling of the vast deep-sea habitat, however, makes it very difficult to establish the ranges of less common foraminiferal species, and endemism may be more prevalent than currently realized. On continental slopes, some species have restricted distributions, but wide-ranging bathyal species that exhibit considerable morphological variation are more common. This may be linked to the greater heterogeneity of continental slopes compared with oceans basins. Improved knowledge of deep-sea foraminiferal biogeography requires sound morphology-based taxonomy combined with molecular genetic studies.

Oxygen Isotope Stratigraphy

Abstract: Variations in the 18 O/ 16 O ratios of marine fossils and microfossils record changes in seawater 18 O/ 16 O and temperature and form the basis for global correlation. Relying on previous compilations and new data, this chapter presents oxygen isotope curves for Phanerozoic foraminifera, mollusks, brachiopods, and conodonts, and Precambrian limestones, dolostones, and cherts. Periodic oxygen-isotopic variations in deep-sea foraminifera define marine isotope stages that, when combined with biostratigraphy and astronomical tuning, provide a late Cenozoic chronostratigraphy with a resolution of several thousand years. Oxygen isotope events of late Cenozoic, Mesozoic, and Paleozoic age serve as chemostratigraphic markers for regional and global correlation. Precambrian oxygen isotope stratigraphy, however, is hampered by the lack of unaltered authigenic marine sediments.

The Toarcian oceanic anoxic event in the Western Saharan Atlas, Algeria (North African paleomargin): Role of anoxia and productivity

Abstract: We used an integrated analysis of benthic foraminiferal assemblages, geochemical proxies (paleoproductivity, redox, and detrital proxies), and C and O stable isotopes to characterize the Toarcian oceanic anoxic event along the North African paleomargin, more precisely in the Saharan Atlas (Algeria). Special emphasis was placed on time intervals previous to the anoxic event and the recovery of normal conditions after this event. The Fisher9s alpha diversity of the foraminiferal assemblages decreased with respect to the end of the Pliensbachian in the polymorphum Zone, with lower values of shallow infaunal forms and an increase in opportunists ( Reinholdella , Lenticulina , and Eoguttulina ). This indicates fluctuations in the oxygenation degree of the infaunal microhabitat in the polymorphum Zone despite the fact that redox proxies do not show any fluctuations, indicating that dysoxic conditions were not reached. The lower part of the levisoni Zone reflects an abrupt paleoenvironmental change, evidenced by the extinction of foraminifera, enrichment in redox-sensitive elements, increase in detrital and paleoproductivity proxies, and fluctuations of δ 13 C and δ 18 O. An anoxic or strongly dysoxic event happened by the polymorphum - levisoni zone boundary in the Western Saharan Atlas, coincident with increasing eolian detrital input and paleoproductivity. The upper part of the levisoni Zone represents a return to normal oxic conditions, and the slow recovery of benthic foraminiferal assemblages dominated by opportunistic forms ( Lenticulina , Eoguttulina , and Reinholdella ) of low diversity. The Toarcian oceanic anoxic event occurred in a generalized transgression that may have favored water stratification and confinement of bottom waters in the subbasins developed in the Atlasic domain. This research demonstrates the potential of the integration of data from foraminiferal assemblages and a wide range of geochemical proxies for understanding anoxic events during the Mesozoic.

Climatic forcing of Quaternary deep-sea benthic communities in the North Pacific Ocean

Abstract: There is growing evidence that changes in deep-sea benthic ecosystems are modulated by climate changes, but most evidence to date comes from the North Atlantic Ocean. Here we analyze new ostracod and published foraminiferal records for the last 250,000 years on Shatsky Rise in the North Pacific Ocean. Using linear models, we evaluate statistically the ability of environmental drivers (temperature, productivity, and seasonality of productivity) to predict changes in faunal diversity, abundance, and composition. These microfossil data show glacial-interglacial shifts in overall abundances and species diversities that are low during glacial intervals and high during interglacials. These patterns replicate those previously documented in the North Atlantic Ocean, suggesting that the climatic forcing of the deep-sea ecosystem is widespread, and possibly global in nature. However, these results also reveal differences with prior studies that probably reflect the isolated nature of Shatsky Rise as a remote oceanic plateau. Ostracod assemblages on Shatsky Rise are highly endemic but of low diversity, consistent with the limited dispersal potential of these animals. Benthic foraminifera, by contrast, have much greater dispersal ability and their assemblages at Shatsky Rise show diversities typical for deep-sea faunas in other regions. Statistical analyses also reveal ostracod-foraminferal differences in relationships between environmental drivers and biotic change. Rarefied diversity is best explained as a hump-shaped function of surface productivity in ostracods, but as having a weak and positive relationship with temperature in foraminifera. Abundance shows a positive relationship with both productivity and seasonality of productivity in foraminifera, and a hump-shaped relationship with productivity in ostracods. Finally, species composition in ostracods is influenced by both temperature and productivity, but only a temperature effect is evident in foraminifera. Though complex in detail, the global-scale link between deep-sea ecosystems and Quaternary climate changes underscores the importance of the interaction between the physical and biological components of paleoceanographical research for better understanding the history of the biosphere.

Pattern and timing of the northwestern Barents Sea Ice Sheet deglaciation and indications of episodic Holocene deposition

Abstract: The origin of two acoustic sediment units has been studied based on lithological facies, chronology and benthic stable isotope values as well as on foraminifera and clay mineral assemblages in six marine sediment cores from Kveithola, a small trough west of Spitsbergenbanken on the western Barents Sea margin. We have identified four time slices with characteristic sedimentary environments. Before c. 14.2 cal. ka, rhythmically laminated muds indicate extensive sea ice cover in the area. From c. 13.9 to 14.2 cal. ka, muds rich in ice-rafted debris were deposited during the disintegration of grounded ice on Spitsbergenbanken. From c. 10.3 to 13.1 cal. ka, sediments with heterogeneous lithologies suggest a shifting influence of suspension settling and iceberg rafting, probably derived from a decaying Barents Sea Ice Sheet in the inner-fjord and land areas to the north of Kveithola. Holocene deposition was episodic and characterized by the deposition of calcareous sands and shell debris, indicative of strong bottom currents. We speculate that a marked erosional boundary at c. 8.2 cal. ka may have been caused by the Storegga tsunami. Whilst deposition was sparse during the Holocene, Kveithola acted as a sediment trap during the preceding deglaciation. Investigation of the deglacial sediments provides unprecedented details on the dynamics and timing of glacial retreat from Spitsbergenbanken.

Possible early foraminiferans in post-Sturtian (716−635 Ma) cap carbonates

Abstract: Foraminifera are an ecologically important group of modern heterotrophic amoeboid eukaryotes whose naked and testate ancestors are thought to have evolved ∼1 Ga ago. However, the single-chambered agglutinated tests of these protists appear in the fossil record only after ca. 580 Ma, coinciding with the appearance of macroscopic and mineralized animals. Here we report the discovery of small, slender tubular microfossils in the Sturtian (ca. 716–635 Ma) cap carbonate of the Rasthof Formation in Namibia. The tubes are 200–1300 μm long and 20–70 μm wide, and preserve apertures and variably wide lumens, folds, constrictions, and ridges. Their sometimes flexible walls are composed of carbonaceous material and detrital minerals. This combination of morphologic and compositional characters is also present in some species of modern single-chambered agglutinated tubular foraminiferans, and is not found in other agglutinated eukaryotes. The preservation of possible early Foraminifera in the carbonate rocks deposited in the immediate aftermath of Sturtian low-latitude glaciation indicates that various morphologically modern protists thrived in microbially dominated ecosystems, and contributed to the cycling of carbon in Neoproterozoic oceans much before the rise of complex animals.

Ecological partitioning and diversity in tropical planktonic foraminifera

Abstract: Background Ecological processes are increasingly being viewed as an important mode of diversification in the marine environment, where the high dispersal potential of pelagic organisms, and a lack of absolute barriers to gene flow may limit the occurrence of allopatric speciation through vicariance. Here we focus on the potential role of ecological partitioning in the diversification of a widely distributed group of marine protists, the planktonic foraminifera. Sampling was conducted in the tropical Arabian Sea, during the southwest (summer) monsoon, when pronounced environmental conditions result in a strong disparity in temperature, salinity and productivity between distinct northern and southern water masses.

Abrupt planktic foraminiferal turnover across the Niveau Kilian at Col de Pré-Guittard (Vocontian Basin, southeast France): new criteria for defining the Aptian/Albian boundary

Abstract: A detailed and quantitative study of foraminiferal assemblages across the Niveau Kilian in the Col de Pre-Guittard section (Vocontian Basin, southeast France) ably documents the planktic foraminiferal turnover across the Aptian - Albian boundary interval. The latest Aptian assemblage is dominated by few long-ranging Hedbergella and large-sized Paraticinella that completely disappear near the base of the Niveau Kilian organic-rich level. Planktic foraminiferal assemblages from across the Niveau Kilian to the top of the studied section are composed of minute, but very distinctive smooth-surfaced species of Microhedbergella miniglobularis and Mi. renilaevis. The appearance of Mi. renilaevis in the middle part of the Niveau Kilian represents a major step in the evolution and diversification of the Albian planktic fauna. The lowest occurrence of this taxon is recorded immediately above the extinction level of the Aptian hedbergellids and corresponds with a dramatic decrease in the number of planktic and benthic foraminifera specimens, with a 1 ‰ negative δ13C excursion in bulk carbonate, and evidence for regional rise in sea-surface temperature. Our careful study of the species composition permits refinement of the previous biozonation by using the appearance datum of Mi. renilaevis as a zonal boundary event. Changes include redefinition of the top of the Microhedbergella miniglobularis Zone and designation of a new Microhedbergella renilaevis Zone. The same sequence of events was reported from several deep-sea sites in the Atlantic and Indian Oceans. Therefore, documentation of the planktic foraminiferal turnover, combined with the carbon-isotope stratigraphy in the Col de Pre-Guittard section, provide new criteria for defining the Global Boundary Stratotype Section and Point for the base of the Albian Stage in a stratigraphically complete succession.

Anoxia : evidence for eukaryote survival and paleontological strategies

Abstract: Introduction, Joseph Seckbach. Stepping into the book of Eukaryotes and Anoxia, Alexander Altenbach, Joan Bernhard, Joseph Seckbach. List of Authors and their Addresses. List of External Reviewers and Referees. Acknowledgment to authors, reviewers and any special people who assisted. PART I: GENERAL INTRODUCTION Anaerobic eukaryotes, Tom Fenchel. Biogeochemical reactions in marine sediments underlying anoxic water bodies, Tina Treude. Diversity of anaerobic prokaryotes and eukaryotes - breaking long-established dogmas, Aharon Oren. PART II: FUNCTIONAL BIOCHEMISTRY The biochemical adaptations of mitochondrion-related organelles of parasitic and free-living microbial eukaryotes to low oxygen environments, Anastasios Tsaousis et al. Hydrogenosomes and mitosomes: mitochondrial adaptations to life in anaerobic environments, Rob De Graaf and Johannes Hackstein. Adapting to hypoxia: lessons from vascular endothelial growth factor, Nina and Andy Levy. PART III: MANAGING ANOXIA Magnetotactic protists at the oxic-anoxic transition zones of coastal aquatic environments, Dennis A. Bazylinski et al. A novel ciliate (Ciliophora: Hypotrichida) isolated from bathyal anoxic sediments, David J. Baudoin et al. The wood-eating termite hindgut: diverse cellular symbioses in a microoxic to anoxic environment, Michael F. Dolan. Ecological and experimental exposure of insects to anoxia reveals suprising tolerance, William W. Hoback. The unusual response of encysted embryos of the animal extremophile, Artemia franciscana, to prolonged anoxia, James S. Clegg. Survival of tardigrades in extreme environments - a model animal for astrobiology, Daiki Horikawa. Long-term anoxia-tolerance in flowering plants, Robert M.M. Crawford. PART IV: FORAMINIFERA Benthic Foraminifera: inhabitants of low-oxygen environments, Karoliina Koho and Elisa Pina-Ochoa. Ecological and biological response of benthic Foraminifera under oxygen-depleted conditions: evidence from laboratory approaches, Petra Heinz and Emmanuele Geslin. The response of benthic Foraminifera to low-oxygen conditions of the Peruvian oxygen minimum zone, Jurgen Mallon et al. Benthic foraminiferal communities and microhabitat selection on the continental shelf off central Peru, Jorge Cardich et al. PART V: ZONES AND REGIONS Living assemblages from the "Dead Zone" and naturally occurring hypoxic zones, Kurt R. Buck et al. The return of shallow shelf seas as extreme environments: Anoxia and macrofauna reactions in the northern Adriatic Sea, Michael Stachowitsch et al. Meiobenthos of the oxic/anoxic interface in the south-western region of the Black Sea: abundance and taxonomic composition, Nelli G. Sergeeva et al. The role of eukaryotes in the anaerobic food web of stratified lakes, Alessandro Sacca. The anoxic Framvaren fjord as a model system to study protistan diversity and evolution, Thorsten Stoeck and Anke Behnke. Characterizing an anoxic habitat: sulphur bacteria in a meromictic alpine lake, Giesela Fritz et al. Ophel, the newly discovered hypoxic chemolitho-autotrophic groundwater biome - a window to ancient animal life, Franzis Dov Por. Microbial eukaryotes in the marine subsurface? Virginia P. Edgcomb and Jennifer Biddle. PART VI: MODERN ANALOGS AND TEMPLATES FOR EARTH HISTORY On the use of stable nitrogen isotopes in present and past anoxic environments, Ulrich Struck. Carbon and nitrogen isotopic fractionation in Foraminifera: possible signatures from anoxia, Alexander V. Altenbach et al. The functionality of pores in benthic Foraminifera in view of bottom water oxygenation. A review, Nicolaas Glock et al. Anoxia-dysoxia at the sediment-water interface of the southern Tethys in the late Cretaceous: Mishash formation, southern Israel, Ahuva Almogi-Labin. Styles of agglutination in benthic Foraminifera from modern Santa Barbara basin sediments and the implications of finding fossil analogs in Devonian and Mississippian black shales, Jurgen Schieber. Did redox conditions trigger test templates in Proterozoic Foraminifera? Alexander V. Altenbach and Maren Gaulke. The relevance of anoxic and agglutinated benthic Foraminifera to the possible Archean evolution of eukaryotes, Wladyslaw Altermann et al. PART VII: FINALS.

Nitrogen isotopic composition of planktonic foraminifera from the modern ocean and recent sediments

Abstract: We investigated the controls on the δ15N values of shell-bound organic matter of planktonic foraminifera (foraminifera-bound δ15N, or FB-δ15N) The bulk biomass δ15N of live foraminifera collected from plankton tows at Sta S in the Sargasso Sea is within ∼1‰ of the FB-δ15N of the same species picked from surface sediments from the low-latitude North Atlantic The FB-δ15N value in the surface sediments is strongly correlated with the δ15N of thermocline nitrate, the dominant source of new N to the euphotic zone The three euphotic-zone-dwelling, symbiotic, spinose species, Globigerinoides ruber, Globigerinoides sacculifer, and Orbulina universa, have a FB-δ15N similar to or slightly higher than that of the nitrate supply to the euphotic zone, whereas the deeper-dwelling, non-spinose, and/or asymbiotic forms have higher δ15N In the Cariaco Basin sediment trap samples, the FB-δ15N of O universa varies substantially (12‰ between the lowest and highest value), in some cases in step with δ15N changes in the bulk sinking N, while the subeuphotic-zone-dwelling, asymbiotic, and/or non-spinose species are generally higher in FB-δ15N and less variable through the time series The higher and less temporally variable FB-δ15N values of the deeper dwellers are consistent with their partial reliance on subsurface suspended particulate nitrogen, the δ15N of which is elevated and relatively stable over time As an alternative, possibly additional explanation for the lower FB-δ15N of the euphotic-zone dwellers (despite their likely tendency to feed on high-δ15N zooplankton), the dinoflagellate symbionts may reduce the δ15N elevation of a foraminifera's biomass relative to its diet by reducing the efflux of low-δ15N ammonium

Distribution of living benthic foraminifera on the northern gulf of cadiz continental shelf

Abstract: Living (stained) benthic foraminiferal faunas were analyzed in 51 surficial sediment samples taken from the northern Gulf of Cadiz continental shelf between the mouths of the Guadiana and Guadalquivir rivers. The distribution and abundance of 26 species with relative abundance >5% were related to water depth, sediment type, river discharge, water temperature, salinity, turbidity, and primary productivity. Hierarchical classification using R- and Q-mode cluster analyses, and individual distributions, allowed these taxa to be categorized into four general groups. Group 1 is represented by Bolivina ordinaria and Hopkinsina atlantica. These species are linked to river discharge, and are associated with muddy sediments. They are considered the most opportunistic species in the assemblage, and are associated with the limits of productivity. Group 2, contains Ammonia beccarii, Eggerelloides scaber, Elphidium gerthi, Quinqueloculina laevigata, and Q. stelligera, and is characteristic of shallow water depths. Its species are associated with different sediment types and their distribution is influenced by river discharge. Group 3 is dominated by Bulimina aculeata, B. elongata, Elphidium excavatum, E. cuvillieri, Epistominella vitrea, and Rectuvigerina phlegeri. These species display the highest abundances between 30–100 m water depths. They prevail in muds associated with weak hydrodynamics, low oxygenation, and high organic matter. Group 4 includes species that are more abundant in deep stations and is divided into two subgroups. Subgroup 4A includes Bolivina catanensis, B. italica, B. striatula, Cassidulina laevigata, Stainforthia sp., Nouria polymorphinoides, and Nouria sp., with higher abundances in one or two samples. Subgroup 4B, with Brizalina dilatata, B. spathulata, Bulimina marginata, Nonionella iridea, N. stella, and N. turgida, has patchy distribution. Higher abundances of Nonionella species off the Guadiana River are related to low temperature and salinity.

Evolutionary ecology of Early Paleocene planktonic foraminifera: size, depth habitat and symbiosis

Abstract: The carbon stable isotope (δ13C) composition of the calcitic tests of planktonic foraminifera has an important role as a geochemical tracer of ocean carbon system changes associated with the Cretaceous/Paleogene (K/Pg) mass extinction event and its aftermath. Questions remain, however, about the extent of δ13C isotopic disequilibrium effects and the impact of depth habitat evolution on test calcite δ13C among rapidly evolving Paleocene species, and the influence this has on reconstructed surface-to-deep ocean dissolved inorganic carbon (DIC) gradients. A synthesis of new and existing multispecies data, on the relationship between δ13C and δ18O and test size, sheds light on these issues. Results suggest that early Paleocene species quickly radiated into a range of depths habitats in a thermally stratified water column. Negative δ18O gradients with increasing test size in some species of Praemurica suggest either ontogenetic or ecotypic dependence on calcification temperature that may reflect depth/light controlled variability in symbiont photosynthetic activity. The pattern of positive δ13C test-size correlations allows us to (1) identify metabolic disequilibrium δ13C effects in small foraminifera tests, as occur in the immediate aftermath of the K/Pg event, (2) constrain the timing of evolution of foraminiferal photosymbiosis to 63.5 Ma, ∼0.9 Myr earlier than previously suggested, and (3) identify the apparent loss of symbiosis in a late-ranging morphotype of Praemurica. These findings have implications for interpreting δ13C DIC gradients at a resolution appropriate for incoming highly resolved K/Pg core records.