Showing papers on "Foraminifera published in 2005"

Radiocarbon Variability in the Western North Atlantic During the Last Deglaciation

Abstract: We present a detailed history of glacial to Holocene radiocarbon in the deep western North Atlantic from deep-sea corals and paired benthic-planktonic foraminifera. The deglaciation is marked by switches between radiocarbon-enriched and -depleted waters, leading to large radiocarbon gradients in the water column. These changes played an important role in modulating atmospheric radiocarbon. The deep-ocean record supports the notion of a bipolar seesaw with increased Northern-source deep-water formation linked to Northern Hemisphere warming and the reverse. In contrast, the more frequent radiocarbon variations in the intermediate/deep ocean are associated with roughly synchronous changes at the poles.

Modern planktic foraminifera

Abstract: Planktic foraminifers are marine protozoans with calcareous Shells and chambered tests. They first appeared in the mid-Jurassic and spread since the mid-Cretaceous over all the world’s oceans. Modern planktic foraminifers evolved since the early Tertiary, when the first spinose species occurred. Most species live in the surface to sub-thermocline layer of the open ocean, and in marginal seas like the Mediterranean, Caribbean, South China Sea, and Red Sea. Planktic foraminifers are absent in shallow marginal seas, for example, the North Sea. Planktic foraminifers respond to food, temperature and chemistry of the ambient seawater. Species abundance varies according to seasons, water masses, and water depths. Symbiont-bearing species depend on light and are restricted to the euphotic zone. Planktic foraminifers constitute a minor portion of total Zooplankton, but are major producers of marine calcareous particles (shells) deposited on the ocean floor where they form the so-called foraminiferal ooze. Planktic foraminifers contribute substantially to the fossil record of marine Sediments and are of high ecologic, paleoceanographic, and stratigraphic significance since the mid-Cretaceous. Radiocarbon (14C) gives an absolute age of shell formation within late Pleistocene and Holocene Sediments. Factors that determine the modern faunal composition are applied to Interpretation of the fossil assemblages, for example, by multiple regression techniques (transfer functions) to yield an estimate on ancient environmental parameters. The chemical composition of the calcareous shell (stable isotopes and trace elements) holds clues to the chemical and physical State of the ambient seawater and is useful in the reconstruction of temperature, chemical State, and biological productivity of the ancient marine environment.

Atlas of Paleogene Cosmopolitan Deep-water Agglutinated Foraminifera

Abstract: A thorough knowledge of dating methods is immensely useful to quaternary geologists and other earth scientists. It constitutes the basis for assigning ages to events in the distant past, as Professor Mike Walker states in his book preface: “My principal purpose is to describe the various dating techniques that are routinely employed in Quaternary science ...”. The present book has a predecessor in J. Lowe & M. Walker earlier classic Reconstructing Quaternary Environments (1997) and contains topics of another book of him entitled Late Quaternary Environmental Changes (1992). The book begins with a documented historical background (Chapter 1) that reviews the development of various dating methods and some fuzzy problems like duration of the Quaternary period, stratigraphy and terminology. Chapters 2 to 4 provide a detailed presentation of different radiometric dating methods, each with its basic principles, problems, and specific applications. Chapter 2 is entirely dedicated to the Radiocarbon dating and describes various types of measurements, sources or error, how to calibrate the radiocarbon timescale, and how to handle some problematic dating materials. Fourteen case studies are covered under the practical aspects related to this method. Chapter 3 describes dating methods using longlived (K/Ar, 40Ar/39Ar, U-series, and cosmogenic nuclides) and short-lived (210Pb, 137Cs, and 32Si) radioactive isotopes. Radiation exposure dating methods (luminescence: TL, OSL; ESR, and fission track) are explained and exemplified in Chapter 4 along with fifteen relevant applications. Chapter 5 provides a thorough and systematic presentation of six dating methods that make use of regular additions of material to organic tissue or sedimentary sequences (dendrochronology, varve sediments, lichenometry, annually layered glacier ice, speleothems, corals, and molluscs). Although, these techniques are basically used for dating Holocene events, some of them (i.e., varves, icelayers, speleothems, and sometimes tree-rings) are widely used to date pre-Holocene sequences. Five relative dating methods (rock surface weathering, obsidian hydration, pedogenesis, amino acid, and fluoride dating) are gathered in Chapter 6. Of these, the author prepared a longer presentation for the amino acid geochronology, for which method, four applications were examined. Chapter 7 is devoted to an in-depth treatment of the techniques for establishing age equivalence, such are oxygen isotope chronostratigraphy, tephrochronology, and paleomagnetic dating. The book is rounded off by Chapter 8 that is dedicated to Dating the future, in which the author is prospecting how the Quaternary dating methods will look a few decades from now on. The book also includes a useful bibliography and at the end of each chapter a series of Notes explain specific terms. The book’s structure proves very workable and all chapters are carefully illustrated. The new book by Mike Walker is well written, the style is clear and easy to read. Therefore is an important contribution to our Quaternary community either as an introduction textbook for both undergraduate and postgraduate students or for other earth science specialists (when considering the large number of specific examples for each dating method). In conclusion, I welcome the publication of this book and highly recommend it to those who are fascinated by locating in time and space different Quaternary events, but not only.

Live foraminiferal faunas from a 2800 m deep lower canyon station from the Bay of Biscay: Faunal response to focusing of refractory organic matter

Abstract: A 2800 m deep station was sampled on three occasions, in January 1999, June 1999 and April 2000, in the lower part of Cap-Ferret Canyon (Bay of Biscay) This area is characterisedby a rapidaccumulation of fine-grainedsediments and by important inputs of reworked organic matter in an intermediate state of decay Diagenetic reactions within the sediment follow the well-established depth sequence resulting from the oxidation of organic deposits by different electron acceptors At our station, live benthic foraminiferal faunas differ strongly from faunas previously collected at nearby open slope sites at a comparable water depth Spectacularly high densities of deep infaunal species are observed in the deeper parts of the sediment for all three sampling periods In our opinion, these high deep infaunal densities are a direct response to the massive flux of partially degraded organic matter, which is slowly introduced into the deeper parts of the sediment, where it induces a rather stable succession of redox gradients Melonis barleeanus lives in the dysoxic part of the sediment whereas Globobulimina affinis appears preferentially close to the zero oxygen boundary Both taxa occupy niches where the highest content of Mn (III, IV)-oxides and -oxihydroxides and Fe (III)-oxides are recorded The fact that most of the geochemical reactions within the sediment are directly or indirectly catalysed by

Turnover of larger foraminifera during the Paleocene-Eocene Thermal Maximum and paleoclimatic control on the evolution of platform ecosystems

Abstract: The larger-foraminifera turnover (LFT) during the Paleocene-Eocene transition constitutes an important step in Paleogene larger-foraminifera evolution, involving a rapid increase in species diversity, shell size, and adult dimorphism. A platform-to-basin transect in Egypt provides new data on timing and causal mechanisms through correlation with planktic biozonations and through integration with regional paleoenvironmental data. The LFT coincides with the boundary between shallow benthic biozones SBZ4 and SBZ5 and closely correlates with the Paleocene-Eocene Thermal Maximum (PETM). Enhanced oligotrophy from the late Paleocene onward favored the diversification of K-strategist larger foraminifera. We suggest that a short-term eutrophication during the PETM led to a temporary decline of extreme K-strategist larger-foraminifera species, providing opportunities for new taxa with different ecological strategies to develop. During post-PETM oligotrophic conditions, these new taxa were able to evolve rapidly and soon dominated early Eocene larger-foraminifera assemblages, whereas many Paleocene taxa gradually disappeared. The success of larger foraminifera during the early Paleogene appears climatically controlled. Because of the vulnerability of corals to high surface-water temperatures, the late Paleocene to early Eocene global warming may have favored larger foraminifera at the expense of corals as the main carbonate-producing component on carbonate platforms at lower latitudes.

Microbial-foraminiferal episodes in the Early Aptian of the southern Tethyan margin: Ecological significance and possible relation to oceanic anoxic event 1a

Abstract: Two regionally significant microbial-foraminiferal episodes (∼150 kyr each) occur within the Early Aptian shallow marine platform in Oman and throughout eastern Arabia. The stratigraphically lower of these two intervals is characterized by isolated or coalescent domes that share similarities with modern, open-marine stromatolites from the Exuma Cays, Bahamas. The upper interval is predominantly built by a problematic Lithocodium/Bacinella consortium in buildup and massive boundstone facies. Based on high-resolution chemostratigraphy, these shoalwater intervals are coeval with oceanic anoxic event 1a (OAE1a; Livello Selli). Field evidence demonstrates that the buildup episodes alternate with stratigraphic intervals dominated by rudist bivalves. This biotic pattern is also recognized in other coeval Tethyan sections and is perhaps a characteristic shoalwater expression of the OAE1a. The short-lived regional expansions of this microbial-foraminiferal out-of-balance facies cannot be explained by local environmental factors (salinity and oxygen level) alone and the buildup consortia do not occupy stressed refugia in the absence of grazing metazoans. Judging from recent analogues, the main fossil groups, i.e. microbial assemblages, macroalgae, larger sessile foraminifera, and rudist bivalves, all favoured elevated trophic levels but with different tolerance limits. The implication of this is that the influence of palaeofertility events, possibly related to OAE1a, on carbonate platform community structures must be investigated. The observations made in these coastal sections are a significant first step for the improved understanding of the Early Aptian period of biotic, oceanic and climatic change. © 2005 International Association of Sedimentologists.

Species-specific ingestion of organic carbon by deep-sea benthic foraminifera and meiobenthos: In situ tracer experiments

Abstract: We measured organic carbon uptake rates by deep-sea benthic foraminifera and studied differences among species, living depth, and seasons to investigate how these protists contribute to carbon consumption on the deep-sea floor. In situ feeding experiments using

Facies dynamics in Eocene to Oligocene circumalpine carbonates

Abstract: A new concept, termed ‘Facies Dynamics’ (defined as changes of specific carbonate facies types in time and space, which are controlled by phylogenetic, ecological and geological parameters), is introduced. This concept aims to define and interpret spatial and temporal changes of carbonate facies patterns. It is based on Middle Eocene to Early Oligocene shallow-water carbonate facies types from the circumalpine area (north-eastern Italy, northern Slovenia, Austria and southern Bavaria), which are compared with respect to dominating biogenic components and their distributions along a shelf gradient. This comparison has lead to the distinction and definition of 14 Major Facies Types (MFTs), which are dominated by coralline algae, larger and smaller foraminifera, corals and bryozoans. The presence and distribution of these MFTs from three different time slices (Middle Eocene, Late Eocene and Early Oligocene) is compared. Nine aspects of facies dynamics are distinguished: origination, extinction, immigration, emigration, expansion, reduction, stasis, shift, and replacement of MFTs. These changes are controlled by regional changes in ecological parameters, but also by global events, especially extinction patterns at the Middle/Late Eocene boundary and at the Eocene/Oligocene boundary.

An evaluation of 14C age relationships between co‐occurring foraminifera, alkenones, and total organic carbon in continental margin sediments

Abstract: [ 1] Radiocarbon age relationships between co- occurring planktic foraminifera, alkenones, and total organic carbon in sediments from the continental margins of southern Chile, northwest Africa, and the South China Sea were compared with published results from the Namibian margin. Age relationships between the sediment components are site- specific and relatively constant over time. Similar to the Namibian slope, where alkenones have been reported to be 1000 - 4500 years older than co- occurring foraminifera, alkenones were significantly ( similar to 1000 years) older than co- occurring foraminifera in the Chilean margin sediments. In contrast, alkenones and foraminifera were of similar age ( within 2 sigma error or better) in the NW African and South China Sea sediments. Total organic matter and alkenone ages were similar off Namibia ( age difference TOC alkenones: 200 - 700 years), Chile ( 100 - 450 years), and NW Africa ( 360 - 770 years), suggesting minor contributions of preaged terrigenous material. In the South China Sea, total organic carbon is significantly ( 2000 - 3000 years) older owing to greater inputs of preaged terrigenous material. Age offsets between alkenones and planktic foraminifera are attributed to lateral advection of organic matter. Physical characteristics of the depositional setting, such as seafloor morphology, shelf width, and sediment composition, may control the age of co- occurring sediment components. In particular, offsets between alkenones and foraminifera appear to be greatest in deposition centers in morphologic depressions. Aging of organic matter is promoted by transport. Age offsets are correlated with organic richness, suggesting that formation of organic aggregates is a key process.

Variation in the diversity and composition of benthic taxa as a function of distance offshore, depth and exposure in the Spermonde Archipelago, Indonesia

Abstract: The aims of this study are to compare cross-shelf variation in diversity and community composition of four benthic taxa (sea urchins, sponges, corals and foraminifera) in the reefs of the Spermonde Archipelago, Indonesia, and relate this variation to cross-shelf environmental parameters, i.e. distance offshore, depth and exposure to oceanic currents. Rarefied species richness and Shannon's H ′ varied unimodally with the distance offshore and depth for all taxa (except sea urchins) and were highest at intermediate distances offshore and depths. There was no significant association between evenness and distance offshore. Evenness did, however, vary with depth and exposure. Overall, models using distance offshore, depth and exposure explained most of the variation in sponge and coral diversity but substantially less variation in foraminifera diversity. Variation in composition depended on distance offshore, depth and exposure although the relative importance of these variables differed among taxa. Depth was the most important parameter for sponges, corals and foraminifera but not for sea urchins. Sponge and coral assemblages differed markedly from in-to-off-shore but there was relatively little variation in foraminifera assemblages with most foraminifera species having broad cross-shelf distributions. Foraminifera assemblages on the contrary differed markedly between exposed and sheltered reef environments; species in exposed reef environments, for example, consisted of species with distinct strategies for coping with the increased hydrodynamic energy. In summary, this study shows that benthic taxa in the Spermonde are distributed along continuous gradients (in-to-off-shore and shallow-to-deep) in addition to occupying discrete habitats related to reef exposure.

Calcium isotope (δ44/40Ca) variations of Neogene planktonic foraminifera

Abstract: Measurements of the calcium isotopic composition (δ44/40Ca) of planktonic foraminifera from the western equatorial Pacific and the Indian sector of the Southern Ocean show variations of about 0.6‰ over the past 24 Myr. The stacked δ44/40Ca record of Globigerinoides trilobus and Globigerina bulloides indicates a minimum in δ44/40Casw (seawater calcium) at 15 to 16 Ma and a subsequent general increase toward the present, interrupted by a second minimum at 3 to 5 Ma. Applying a coupled calcium/carbon cycle model, we find two scenarios that can explain a large portion of the observed δ44/40Casw variations. In both cases, variations in the Ca input flux to the ocean without proportional changes in the carbonate flux are invoked. The first scenario increases the riverine calcium input to the ocean without a proportional increase of the carbonate flux. The second scenario generates an additional calcium flux from the exchange of Ca by Mg during dolomitization. In both cases the calcium flux variations lead to drastic changes in the seawater Ca concentrations on million year timescales. Our δ44/40Casw record therefore indicates that the global calcium cycle may be much more dynamic than previously assumed.

The 8200 year B.P. event in the slope water system, western subpolar North Atlantic

Abstract: [1] Stable isotope, trace metal, alkenone paleothermometry, and radiocarbon methods have been applied to sediment cores in the western subpolar North Atlantic between Hudson Strait and Cape Hatteras to reveal the history of climate in that region over the past ∼11 kyr. We focus on cores from the Laurentian Fan, which is known to have rapid and continuous accumulation of hemipelagic sediment. Although results among our various proxy data are not always in agreement, the weight of the evidence (alkenone sea surface temperature (SST), δ18O and abundance of Globigerinoides ruber) indicates a continual cooling of surface waters over Laurentian Fan, from about 18°C in the early Holocene to about 8°C today. Alternatively, Mg/Ca data on planktonic foraminifera indicate no systematic change in Holocene SST. The inferred long-term decrease in SST was probably driven by decreasing seasonality of Northern Hemisphere insolation. Two series of proxy data show the gradual cooling was interrupted by a two-step cold pulse that began 8500 years ago, and lasted about 700 years. Although this event is associated with the final deglaciation of Hudson Bay, there is no δ18O minimum anywhere in the Labrador Sea, yet there is some evidence for it as far south as Cape Hatteras. Finally, although the 8200 year B.P. event has been implicated in decreasing North Atlantic ventilation, and hence widespread temperature depression on land and at sea, we find inconsistent evidence for a change at that time in deep ocean nutrient content at ∼4 km water depth.

Intertidal mangrove foraminifera from the central great barrier reef shelf, australia: implications for sea-level reconstruction

Abstract: Contemporary foraminiferal samples and environmental information were collected from three fringing mangrove environments (Sandfly Creek Transect 1 and 2, and Cocoa Creek) in Cleveland Bay, and an estuarine mangrove environment (Saunders Creek) in Halifax Bay, on the central Great Barrier Reef (GBR) coastline, Australia, to elucidate the relationship of the foraminiferal assemblages with the environment. The data support the vertical zonation concept, which suggests that the distribution of foraminifera in the intertidal zone is usually a direct function of elevation, with the duration and frequency of subaerial exposure as the most important factor. An agglutinated foraminiferal assemblage dominated by Miliammina fusca, Trochammina inflata, Ammotium directum and Haplophragmoides sp. exists at the landward edge of the field sites, in a zone between just above Mean Low Water of Neap Tides to Highest Astronomical Tide level (a vertical range of 1.8 m). In addition, a foraminiferal assemblage dominated by Ammonia aoteana is found at all sites, existing between just below Mean Low Water of Neap Tides and Mean High Water of Neap Tides (a vertical range of 0.8 m). These assemblages may be used to reconstruct sea level from fossil cores from the area.

Infaunal marsh foraminifera from the outer banks, north carolina, u.s.a.

Abstract: The distribution and abundance patterns of live (rose Bengal stained) and dead, shallow infaunal (0–1 cm depth) and deep infaunal (1 cm depth) benthic foraminifera have been documented at three locations representing different salinity settings on the fringing marshes along the Pamlico Sound and Currituck Sound coasts of North Carolina’s Outer Banks. Two cores taken at each site represent the lower and higher marsh. Twenty-two taxa were recorded as live. Of these, eight taxa were found only at shallow infaunal depths; the other 14 taxa occur at deep infaunal depths in one or more cores. Only Jadammina macrescens and Tiphotrocha comprimata were recorded as living in all six cores. The distributions of the other taxa were restricted by combinations of the criteria of infaunal depth, salinity regime and location on the marsh. The tests of infaunal foraminifera were generally more likely to be preserved in the lower marsh than the higher marsh at low- and intermediate-salinity sites. The opposite pattern was evident at the high-salinity site but this may be due to the low numbers of deep infaunal specimens recovered. Arenoparrella mexicana, Haplophragmoides wilberti, Jadammina macrescens and Trochammina inflata are the most resistant taxa, whereas Miliammina fusca is the species whose tests are most likely to be lost to post-mortem degradation. In five of six cores, foraminiferal assemblages and populations do not differ significantly with depth which suggests that the foraminifera of the 0–1 cm depth interval provide an adequate model upon which paleoenvironmental (including former sea level) reconstructions can be based.

The deglacial history of surface and intermediate water of the Bering Sea

Abstract: The lithology of deglacial sediments from the Bering Sea includes intervals of laminated or dysaerobic sediments. These intervals are contemporaneous with the occurrence of laminated sediments from the California margin and Gulf of California, which suggests widespread low-oxygen conditions at intermediate depths in the North Pacific Ocean. The cause could be reduced intermediate water ventilation, increased organic carbon flux, or a combination of the two. We infer abrupt decreases of planktonic foraminifer d 18 O at 14,400 and 11,650 yr BP, which may be a combination of both freshening and warming. On the Shirshov Ridge, the abundance of sea-ice diatoms of the genus Nitzschia reach local maxima twice during the deglaciation, the latter of which may be an expression of the Younger Dryas. These findings expand the extent of the expression of deglacial millennial-scale climate events to include the northernmost Pacific. r 2005 Elsevier Ltd. All rights reserved.

The myth of the brackish Sarmatian Sea

Abstract: The biota of the 1.5 Ma period of the Middle Miocene Sarmatian of the Central Paratethys lack stenohaline components. This was the reason to interpret the Sarmatian stage as transitional between the marine Badenian and the lacustrine Pannonian stages. However, our new data indicate that brackish water conditions could not have prevailed. Sarmatian foraminifera, molluscs, serpulids, bryozoans, dasycladacean and corallinacean algae as well as diatoms clearly indicate normal marine conditions for the entire Sarmatian. During the Lower Sarmatian, however, a sea-level lowstand forced the development of many marginal marine environments. During the Late Sarmatian a highly productive carbonate factory of oolite shoals, mass-occurrences of thick-shelled molluscs and larger foraminifera, as well as marine cements clearly point to normal marine to hypersaline conditions. This trend is not restricted to the western margin of the Pannonian Basin System but can be observed in the entire Central and even Eastern Paratethys.

Benthic foraminiferal recovery after recent turbidite deposition in cap breton canyon, bay of biscay

Abstract: The vertical distribution of living (rose Bengal stained) benthic foraminifera from three multiple cores from Cap Breton Canyon, Bay of Biscay, France, has been investigated with the objective of monitoring the recolonization and subsequent evolution of the foraminiferal fauna following the deposition of a turbidite layer. The first samples, taken in May 2000 in the axis of Cap Breton Canyon, contained a young turbiditic sequence, most likely deposited during the heavy storm of December 1999. Four months after this sedimentological event, the composition of the living benthic foraminiferal fauna was almost monospecific in the >150 μm fraction, which contained mainly Technitella melo, a species which is otherwise very rare or absent in the Cap Breton Canyon and open slope assemblages. This species was accompanied in the 63–150 μm fraction by adult specimens of Cassidulina carinata and Fursenkoina bradyi, and exclusively juvenile specimens of Bolivina subaenariensis and Bulimina marginata. This fauna represents the first stage of foraminiferal colonization after the turbidite deposition. The samples taken one year later, in June and September 2001, at approximately the same location, contained a more variable foraminiferal assemblage strongly dominated by Bolivina subaenariensis. Foraminiferal assemblages in samples taken just below the successive turbidite sequences contained nearly the same faunal elements as the surface assemblages sampled in 2001. The benthic foraminiferal assemblages from the canyon axis sampled in 2001 show the same composition as other canyon axis faunas dominated by B. subaenariensis. We suggest that the recovery of the foraminiferal faunas in this extremely unstable environment takes about 6–9 months, and that the community structure more or less permanently stays in an early stage of ecosystem recolonization.

Pollution monitoring in two north american estuaries: historical reconstructions using benthic foraminifera

Abstract: Both surface and core studies from two highly impacted estuaries (New Bedford Harbor, Massachusetts, USA and Halifax Harbour, Nova Scotia, Canada) were carried out to determine if benthic foraminifera could be used to detect changes through time in these areas. New Bedford Harbor is in a highly industrialized area that has undergone severe environmental stresses from a variety of sources for almost 400 years, and has been declared an U.S. Environmental Protection Agency (EPA) Superfund site (i.e., a site so impacted that a special EPA fund is set up to clean it up in designated time frame). Halifax Harbour has been subjected mostly to domestic pollution (i.e., organic carbon produced by human wastes), rather than industrial (chemical) pollution since the founding of the city in 1749. Although many geochemical studies have been done in both estuaries, there are few baseline data on the biota. In this paper we use benthic foraminiferal assemblages retrieved from sediment cores to reconstruct biotic changes of the recent past. It is then possible to correlate faunal changes with already known geochemical parameters. The character of the pollution has changed in New Bedford Harbor as remediation efforts have taken hold. This change was detected with the foraminifera. One outcome is that deformities among one species, Haynesina orbiculare, appear to occur simultaneously with high polychlorinated biphenyls (PCB’s) in the sediments. In Halifax Harbour, where the largest impact is due to high organic input from domestic sources, species tolerant of low-oxygen conditions are most prominent at present. Core studies show that prior to the rapid growth of Halifax (in the 1960s) the organic input was much lower than at present. The higher input of organic carbon (OC) at present is indicated by foraminiferal species tolerant of high OC in cores since 1960, generally those with agglutinated as opposed to calcareous tests. We define industrial vs. OC pollution in sediments using foraminifera as proxies, and further, the environmental history is accurately depicted without original baseline data. Data from these two estuaries can be compared to other sites where degradation may be in different stages, which can be assessed by looking at foraminiferal faunas in those areas.

A paleoenvironmental standard section for Early Ilerdian tropical carbonate factories (Corbieres, France; Pyrenees, Spain)

Abstract: Early Ilerdian (Early Eocene, Shallow Benthic Zones 5 and 6) carbonate systems of the Pyrenees shelf were deposited after a time of severe climatic (‘Paleocene–Eocene Thermal Maximum, PETM’) and phylogenetic (‘Larger Foraminifer Turnover’) changes. They reflect the radiation of nummulitid, alveolinid, and orbitolitid larger foraminifera after remarkable biotic changes at the end of the Paleocene, and announce their subsequent flourishing in the Middle Eocene. A paleoenvironmental model for tropical carbonate environments of this particular time interval is provided herein. During the Early Ilerdian, the inner and middle ramp deposits from Minerve, Campo and Serraduy revealed the end-member of a tropical carbonate factory with carbonate production dominated by the end-members of biotically (photo-autotrophic skeletal) controlled and biotically induced carbonate precipitation. Inner platform environments are dominated by alveolinids and in part by orbitolitids, middle platform environments are dominated by nummulitids. Corals are present, but they do not form reefs, which is a typical feature for the Eocene. Nummulite shoal complexes, which are well-known from the Middle Eocene are also absent during the studied Early Ilerdian interval, which may reflect the early evolutionary stage of this group.

Climatic patterns revealed by pollen and oxygen isotope records across the Matuyama–Brunhes Boundary in the central Mediterranean (southern Italy)

Abstract: A c. 50 m thick section located in the Crotone Basin (southern Italy) was investigated using oxygen isotopes, pollen and planktonic foraminifera. The section records two complete trans- gressive-regressive cycles mainly driven by glacio-eustasy. Biostratigraphy and oxygen isotope chronology indicate that the section spans from Marine Isotope Stage (MIS) 22 (c. 0.87 Ma) to MIS 18.3 (c. 0.73 Ma), thus straddling the Matuyama-Brunhes (M-B) boundary which occurs in the middle of MIS 19. The rich pollen assemblages provide a unique record of the vegetation in the central Mediterranean during the Early-Middle Pleistocene climatic transition. Interglacials are characterized by a mesothermic vegetation similar to the present day, whereas a rain-demanding conifer forest dominates the glacials of MIS 20 and MIS 18. This is unexpected because it is gener- ally considered that during the Pleistocene, glacials in central Mediterranean were characterized by steppe (arid) conditions. By contrast, arid conditions occur during the deglaciations. These results are inconsistent with the widespread practice of linking glacials with arid conditions in the central Mediterranean during Pliocene and Early Pleistocene times. This study emphasizes the need to establish more accurate land-sea correlation.

Ocean climate variability in the eastern North Atlantic during interglacial marine isotope stage 11: A partial analogue to the Holocene?

Abstract: Similar orbital geometry and greenhouse gas concentrations during marine isotope stage 11 ( MIS 11) and the Holocene make stage 11 perhaps the best geological analogue period for the natural development of the present interglacial climate. Results of a detailed study of core MD01-2443 from the Iberian margin suggest that sea surface conditions during stage 11 were not significantly different from those observed during the elapsed portion of the Holocene. Peak interglacial conditions during stage 11 lasted nearly 18 kyr, indicating a Holocene unperturbed by human activity might last an additional 6-7 kyr. A comparison of sea surface temperatures ( SST) derived from planktonic foraminifera for all interglacial intervals of the last million years reveals that warm temperatures during peak interglacials MIS 1, 5e, and 11 were higher on the Iberian margin than during substage 7e and most of 9e. The SST results are supported by heavier delta(18)O values, particularly during 7e, indicating colder SSTs and a larger residual ice volume. Benthic delta(13)C results provide evidence of a strong influence of North Atlantic Deep Water at greater depths than present during MIS 11. The progressive ocean climate deterioration into the following glaciation is associated with an increase in local upwelling intensity, interspersed by periodic cold episodes due to ice- rafting events occurring in the North Atlantic.