Planktic Foraminiferal Species Research Articles

Globorotalia truncatulinoides as indicator of Subtropical Convergence and thermocline change during the late Quaternary in the Southeast Atlantic

Planktic foraminifera in biogenic sediments are widely applied as palaeoceanographic tools and the abundances of Globorotalia truncatulinoides have been used over the past few decades as indicators of upper water column changes over geologic time. The two morphological coiling directions of this species (sinistral and dextral) can provide valuable insight into how the upper water masses of the South Atlantic vary in response to climate change. This study aims to document and analyse the abundances of the planktic foraminiferal species G. truncatulinoides and its two morphological coiling directions in two cores from the continental slope of western South Africa at >3500 m water depth to assess the response of upper water masses to Quaternary climate change. The relative abundances of total G. truncatulinoides in the >125 μm size fraction, abundances of the dextral and sinistral forms in the >212 μm fraction and the division into further size fractions (212 μm, 250 μm, 300 μm, 355 μm, >400 μm) were analysed and considered to determine whether these abundances can be related to oceanographic regime shifts in the eastern South Atlantic during the late Pleistocene from MIS 6 to MIS 1. It was found that the Subtropical Convergence was located at a more southern location during MIS 5 and MIS 1, which allows for warmer subtropical species to increase in abundance with increasing Agulhas leakage around the southwestern margin. The thermocline is interpreted to have deepened during glacial terminations and interglacial periods when productivity was relatively lower and temperatures increased. The size fraction of the sinistral form in the >355 μm is dominant in MIS 5, MIS 3 and MIS1, indicating implications for the use of this species at certain size ranges. This study therefore indicates that G. truncatulinoides is a useful tracer of past Quaternary oceanographic changes along the western margin of South Africa, particularly when the coiling directions at the larger size fraction is taken into account.

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ13C) of shallow dwelling planktic foraminifera over the past 160 kyr

Abstract. Laboratory experiments showed that the isotopic fractionation of δ13C and of δ18O during calcite formation of planktic foraminifera are species-specific functions of ambient CO32- concentration. This effect became known as the carbonate ion effect (CIE), whose role for the interpretation of marine sediment data will be investigated here in an in-depth analysis of the 13C cycle. For this investigation, we constructed new 160 kyr long mono-specific stacks of changes in both δ13C and δ18O from either the planktic foraminifera Globigerinoides ruber (rub) or Trilobatus sacculifer (sac) from 112 and 40 marine records, respectively, from the wider tropics (latitudes below 38°). Both mono-specific time series Δ(δ13Crub) and Δ(δ13Csac) are very similar to each other, and a linear regression through a scatter plot of both data sets has a slope of ∼ 0.99 – although the laboratory-based CIE for both species differs by a factor of nearly 2, implying that they should record distinctly different changes in δ13C, if we accept that the carbonate ion concentration changes on glacial–interglacial timescales. For a deeper understanding of the 13C cycle, we use the Solid Earth version of the Box model of the Isotopic Carbon cYCLE (BICYLE-SE) to calculate how surface-ocean CO32- should have varied over time in order to be able to calculate the potential offsets which would by caused by the CIE quantified in culture experiments. Our simulations are forced with atmospheric reconstructions of CO2 and δ13CO2 derived from ice cores to obtain a carbon cycle which should at least at the surface ocean be as close as possible to expected conditions and which in the deep ocean largely agrees with the carbon isotope ratio of dissolved inorganic carbon (DIC), δ13CDIC, as reconstructed from benthic foraminifera. We find that both Δ(δ13Crub) and Δ(δ13Csac) agree better with changes in simulated δ13CDIC when ignoring the CIE than those time series which were corrected for the CIE. The combination of data- and model-based evidence for the lack of a role for the CIE in Δ(δ13Crub) and Δ(δ13Csac) suggests that the CIE as measured in laboratory experiments is not directly transferable to the interpretation of marine sediment records. The much smaller CIE-to-glacial–interglacial-signal ratio in foraminifera δ18O, when compared to δ13C, prevents us from drawing robust conclusions on the role of the CIE in δ18O as recorded in the hard shells of both species. However, theories propose that the CIE in both δ13C and δ18O depends on the pH in the surrounding water, suggesting that the CIE should be detectable in neither or both of the isotopes. Whether this lack of role of the CIE in the interpretation of planktic paleo-data is a general feature or is restricted to the two species investigated here needs to be checked with further data from other planktic foraminiferal species.

Morphotypical and Geochemical Variations of Planktic Foraminiferal Species in Siberian and Central Arctic Ocean Core Tops

Abstract In this work, we utilize a transect of core top, mid- to late Holocene, sediments from the Eastern Siberian Sea to the central Arctic Ocean, spanning gradients in upper-ocean water column properties, to examine regional planktic foraminiferal species abundances and geochemistry. We present species- and morphotype-specific foraminiferal assemblages at these sites and stable isotope analyses of neogloboquadrinids. We find little variation in planktic species populations, and only small variations in N. pachyderma morphotype distributions, between sites. Spatial averages of N. pachyderma morphotype and N. incompta δ18O values show no significant differences, suggesting a similar calcification depth for all morphotypes of N. pachyderma and N. incompta across our sites, which we estimate to be between ∼ 50–150 m. Values of δ18O of a group of unencrusted specimens delineate a shallower calcification habitat. Neogloboquadrina pachyderma-2 Mg/Ca values yield temperatures outside the range of observations using available calibration equations, pointing toward the need for more Arctic-specific Mg/Ca-temperature calibrations.

Morphotypical and Geochemical Variations of Planktic Foraminiferal Species in Siberian and Central Arctic Ocean Core Tops

Morphotypical and Geochemical Variations of Planktic Foraminiferal Species in Siberian and Central Arctic Ocean Core Tops

NEW GEOGRAPHIC RECORD OF THE UAE PLANKTIC FORAMINIFERA TURBOROTALIA SEMICUNIALENSIS ANAN IN INDIA AND EGYPT

The Late Eocene planktic foraminiferal species Turborotalia semicunialensis Anan with its raised keel in the first two chambers of the last whorl, was recorded recently from the planktic foraminiferal zonation Globigerinatheca index Zone (E16) of Jabal Hafit, United Arab Emirates (UAE). Another forms of this species, but under another names from the Turborotalia cerroazulensis group, were recorded from Cambay Basin, northwest of India (to the east of UAE), and from Wadi Hitan, Fayum area, Western Desert of Egypt (to the west of UAE). This documentation expanded the stratigraphic range of T. semicunialensis from E15 to P16 zonation throughout the Late Eocene. In general, the planktic foraminifera is predominantly considered to be related to open marine environment, photic zone, middle-upper neritic environment (100-200 m water depth).

Palaeoenvironmental changes across the Mid‐ and latest Maastrichtian events: Planktic foraminiferal inference from the Elles section (central Tunisia)

Based on quantitative changes in the Maastrichtian planktic foraminiferal species distribution patterns from the Elles section (central Tunisia), δ13C, δ18O‐based palaeotemperature and inferred proxies (species diversity, ecological associations, and depth ranking), the palaeoenvironment is inferred. Based on Constrained Clustering and corroborated by Non‐metric Multidimensional Scaling (NMDS), four statistically significant intervals are identified. Interval 1 (lower–middle part of CF5 Zone) is marked by a warm, oligotrophic, stable, and well‐stratified upper water column. Interval 2 (upper part of CF5 Zone), here designated as the pre‐Mid‐Maastrichtian Event (MME) event, is marked by stressed, warmer, moderately mesotrophic, and weakly stratified surface waters with an unstable upper water column. Interval 3 (CF4 Zone) encompasses the MME and is marked by warm, stable, mesotrophic surface waters with a moderately well‐stratified upper water column. The upper part of Interval 3, designated as post‐MME, is also marked by mesotrophic conditions, but with increased surface water warming, unstable and stressed conditions. Interval 4 (CF3–CF1 zones) shows the effects of the Indian Deccan volcanism, and is marked by warmer surface waters, mesotrophic, unstable, stressed environmental conditions, with a weakly‐stratified upper water column.

Paleoecological Inferences for Turborotalita Nikolasi (Koutsoukos, 2014) Based on Stable Carbon and Oxygen Isotopes

Abstract The species Turborotalita nikolasi first appeared immediately after the Cretaceous-Paleogene (K-Pg) boundary and is considered the progenitor of all Cenozoic normal perforate species. We present δ18O and δ13C isotope signals of T. nikolasi specimens and compare them with those of mixed-layer (Guembelina cretacea), thermocline (Subbotina trivialis and Chiloguembelina midwayensis), and deep water (Nuttalides truempyi) species with glassy shell preservation from São Paulo Plateau [Deep Sea Drilling Project (DSDP) Site 356]. Turborotalita nikolasi δ18O values are similar to those of G. cretacea, suggesting that both species cohabited the mixed layer. Values of δ13C for T. nikolasi are higher than those of all other planktic foraminiferal species, which may have been due to the presence of photosymbionts, and thus might represent the earliest known record of photosymbiosis for Cenozoic planktic foraminifera. Nuttalides truempyi δ13C values are remarkably high at Site 356, indicating low 12C abundance in deep waters, which could be related to reduced inefficiency of the biological pump in transporting 12C to the bottom of the ocean after the K-Pg boundary during the first ∼300 kyr of the Danian.

PALEONTOLOGY, STRATIGRAPHY, PALEOENVIRONMENT AND PALEOGEOGRAPHY OF FORTY-ONE CAMPANIAN-NEOGENE TETHYAN PLANKTIC AND BENTHIC FORAMINIFERAL GENERA AND SPECIES OF ANAN C- SUBORDERS GLOBIGERININA AND ROTALIINA

This study represents the third part of the erected assemblage of planktic and benthic foraminiferal genera and species of Anan, which related to the Suborders Globigerinina and Rotaliina, after the first and second parts which belongs to the taxa of the Suborders Textulariina, Miliolina and Lagenina (Anan, manuscripts). In this study, eight Plummerita planktic foraminiferal species were erected from Egypt (Misr), Tunisia, Italy, Spain, Caribbean (P. haggagae, P. hodae, P. kellerae, P. premolisilvae, P. elkefensis, P. caribbeanica, P. spainica, P. tunisica), and more one species of Turborotalia (T. semicunialensis). Moreover, thirty-three Rotaliid benthic foraminiferal species were erected from fifteen localities from Northern Tethys (USA, Mexico, Caribbean, Spain, France, Poland, Italy), and Southern Tethys (Chile, Argentina, Tunisia, Egypt, UAE, Iraq, Iran, Pakistan). Three of the identified Rotaliid species are believed here to be new: Orthokarstenia striata, Pleurostomella waeli and Woodella jawdati.

Age of the latest marine sedimentation in the western Kunlun area constrained by planktic foraminifera

Surface uplift of the Tibetan Plateau in the Cenozoic has dramatically affected evolutions of climate, environment, and biota in East Asia. The onset time of plateau uplift can be roughly constrained by the termination of the latest marine sedimentation, which shows large spatial differences in the Tibetan Plateau. In the northwest Tibetan Plateau of the western Kunlun area, the Tielongtan Group represents the latest marine sedimentation. However, the age of its depositional cessation is still unknown. For the first time, we conduct taxonomic, paleoecologic and paleogeographic studies of planktic foraminifera in the limestones of the Tielongtan Group. Despite poor preservation and low abundance, ten planktic foraminiferal species are identified, including Globotruncana falsostuarti, G. cf. linneiana, G. cf. ventricosa, Planohedbergella prairiehillensis, P. cf. yaucoensis, Pseudotextularia nuttalli, Planoheterohelix globulosa, P. cf. praenuttalli, Muricohedbergella holmdelensis and Whiteinella brittnensis. The foraminiferal assemblages suggest an age of late Campanian to Maastrichtian, indicating a shallow, neritic marine environment. Combining available research data from other regions, we show that these planktic foraminifera were widely distributed in the Tarim basin, southern Tibet, and the Mediterranean area during the latest Cretaceous. Our result of planktic foraminifera in the Tielongtan Group implies that the surface uplift of the western Kunlun area did not begin until after ∼76–66 Ma.

Very high Middle Miocene surface productivity on the U.S. mid-Atlantic shelf amid glacioeustatic sea level variability

The Miocene Climatic Optimum (MCO) provides important insights into how the climate system operates under elevated temperatures and atmospheric CO2 levels. Few western North Atlantic paleotemperature or paleoecological records exist from the MCO, despite their importance for understanding both regional and global climate dynamics. Here we present quantitative MCO paleoecological data from the western North Atlantic, specifically from the Baltimore Gas & Electric (BG&E) marine sediment core from southern Maryland, USA. We examine alkenones and planktic foraminifera and document the first sea surface temperature (SST) and productivity estimates for the MCO and the Middle Miocene Climate Transition (MMCT) from the continental shelf. Increased levels of planktic foraminifer species diversity and surface productivity accompany high sea level intervals of the MCO, indicating coastal upwelling. Cooling episodes correlate to unconformities in the BG&E core that reflect sea level lowstands; these and sedimentary cycles tie the record to eccentricity-paced Antarctic ice sheet growth and decay. This dynamic record not only captures the variability in SST, sea level and coastal productivity during the warm MCO and the transition to cooler global temperatures during the MMCT, but it also demonstrates the variability in local conditions within and between intervals of high sea level.

Foraminiferal Distribution Pattern and its Ecological Implications in the Koswari and Van Islands of the Tuticorin Group of Islands

Objectives: The present investigation attempts to map the foraminiferal distribution pattern, its ecological significance, and the elemental composition of the Koswari and Van islands. Methods: Foraminiferal distribution patterns (both planktic and benthic) were recorded, and textural and geochemical analyses were carried out in the present study. Findings: The coastal environments are generally highly dynamic regions of the earth that possess imprints of global climatic variations. The islands of the Gulf of Mannar emerged during the last interglacial period. These islands are getting eroded due to the long-term impact of coral mining and climatic changes. The excess removal of corals from Koswari Island adversely affected the live coral cover of the Island. The Van island is in proximity to the Tuticorin coastal city and one-fourth of the Island has already become submerged due to several natural and anthropogenic factors. Both the islands are affected by the world coral bleaching event witnessed from 2014-2017. This study is an attempt to record how the foraminiferal assemblages of Koswari and Van islands responded to the world coral bleaching event. In the present investigation, we identified fifteen benthic foraminiferal species and two planktic foraminiferal species from both islands. The foraminiferal assemblages mark the abundance of Neorotalia calcar, Quinqueloculina seminulum, Elphidium crispum, Amphistegina lessonii, and Rotalidium annectens. The main ecological parameters which govern the foraminiferal distribution in these islands are coral reef flats, carbonate environments, and shallow coastal waters. Neorotalia calcar and Quinqueloculina seminulum are recorded as the most abundant species of both Koswari and Van islands. N. calcar prefers macroalgal mat as substratum,while the frequent occurrence of deformed tests and stress-tolerant species such as Q. seminulum indicate the influence of pollution in the coastal area. These recorded species are considered characteristic reef benthic foraminifers which prefer coarse sandy substratum. The other abundant species are Elphidium crispum, Amphistegina lessonii, and Rotalidium annectens, which are widely distributed in the inner shelf sediments of Tamil Nadu and Kerala coasts. Textural attributes of the Koswari and Van islands reflect its high energy environment, and the geochemical signature shows the high calcareous content with typical coral reef foraminifera associated with such sediment nature. Novelty: The study tried to map the effect of the global coral bleaching event of 2016 on Koswari and Van islands of the Tuticorin group of Islands in the Gulf of Mannar using foraminifera as a proxy. Keywords: Foraminifera; Coral reefs; Ecology; Coral bleaching; Gulf of Mannar

Revised late Cenozoic foraminifer biostratigraphy of the Eskiköy Formation (Aksu Basin), SW Turkey and its paleoenvironmental conditions

The Aksu Basin, near Antalya, is an important area from many aspects of the geology as it hosts the youngest marine deposits of the western Taurides in southwestern Turkey. These marine deposits play an important role in revealing the response of the Eastern Mediterranean coasts to the post-Zanclean transgression following the Messinian Salinity Crisis and provide a chronological record for detailing the late Cenozoic regional tectonic and sedimentary features. Therefore, biostratigraphic reconstruction of this basin is essential to enhance our understanding of the late Cenozoic evolution of the region and the response of the Eastern Mediterranean realm to climatic shifts. Here, we present an updated foraminifer biostratigraphy of the topmost part of the Eskiköy Formation in the Aksu Basin, a member of the Neogene Antalya basins. The studied Kargı section, located in the northern part of the Aksu Basin, contains planktic foraminifer species such as Neogloboquadrina pachyderma , Globigerinoides tenellus , Globigerinoides obliquus obliquus, and Globoturborotalita rubescens, and benthic foraminifers Bulimina marginata and Saidovina karreriana. These species are important bioevent markers in the Mediterranean Region. Accordingly, we update the stratigraphic range of the Eskiköy Formation found in southwestern Turkey extending it to the Pleistocene falling in MPle1a Neogloboquadrina spp. sx Interval Subzone, more specifically between 1.54 and 1.36 Ma, which previously was considered to be of Pliocene age. This age interval is also in agreement with the previous studies that reported Calabrian-Chibanian aged marine deposits in the Mut Basin, southern Turkey. • Pleistocene bioevent marker planktic and benthic foraminifers were identified. • The sedimentation of the Aksu Basin in southwestern Turkey did not end in the Late Pliocene but continued during the Calabrian. • The Aksu Basin marks a period of low temperatures and lowered sea-level stands during the Calabrian.

Hypothesis testing on the planktic foraminiferal survival model after the KPB mass extinction: evidence from Tunisia and Algeria

A historical review of the extinction, survival, and evolutionary models of planktic foraminifera proposed for the Cretaceous/Paleogene boundary (KPB) mass extinction event sometimes leaves the impression that there is still no conclusive evidence to support any single one of them. Two main models have been put forward: i) catastrophic mass extinction, almost total for some authors, compatible with the geologically instantaneous paleoenvironmental effects of a large meteorite impact (Chicxulub impact, Mexico); and ii) gradual mass extinction, compatible with the paleoenvironmental effects of massive, long-lasting volcanism (Deccan Traps, India). Over the years, a lot of evidence has been proposed supporting one hypothesis or the other, highlighting isotopic (δ18O, δ13C, 87Sr/86Sr) as well as taphonomic, biostratigraphic, quantitative (relative and/or absolute abundance), phylogenetic, and even teratological. We review previous planktic foraminiferal and stable isotope studies, and provide new quantitative and statistical tests from two pelagic sections: the El Kef section (Tunisia), recognized as the most continuous and expanded lowermost Danian section worldwide, and the Sidi Ziane section (Algeria), affected by relevant hiatus in the lower Danian. The results indicate that all the latest Maastrichtian planktic foraminiferal species except those of Guembelitria went extinct exactly at the KPB, supporting the hypothesis of an almost total extinction. In the light of this new evidence, we maintain that the Maastrichtian planktic foraminiferal specimens found worldwide in lower Danian samples could be the result of similar reworking and vertical mixing processes to those at El Kef and Sidi Ziane.

Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf.

Middle Miocene foraminifera from the northern Namibian outer continental shelf are indicators of a period prior to the initiation of the Benguela Upwelling System (BUS). This study provides an update to the occurrence and taxonomy of Miocene foraminifera from the continental margin of Namibia. The taxonomy of 51 benthic and 12 planktic foraminiferal species from the northern Namibian shelf are discussed, their stratigraphic significance given, and their ecological preferences and regional distribution summarised within this study. The identification of extinct planktic foraminifera provided key stratigraphic control for the middle Miocene strata of this region. The taxa identified in this study provide a distinct and different assemblage to the overlying younger strata. Many of the species recorded in this study have not been identified in the region and are reported for the first time from the middle Miocene on the southwestern continental shelf of Africa, off Namibia. A total of 47 species are identified and discussed for the first time from this region. Nineteen species recorded in this study are extinct and eleven taxa reported here have previously only been reported on the genus level on the southwestern shelf of South Africa. Seven benthic species (Amphicoryna scalaris, Marginulina obesa, Glandulina laevigata, Globocassidulina subglobosa, Uvigerina peregrina, Sphaeroidina bulloides and Melonis affinis) and two planktic species (Globigerina bulloides and Orbulina universa) did not disappear from the regional stratigraphy and continued to occur in Plio-Pleistocene to Recent sediments along the southwestern continental shelf of Africa.

Integrated biostratigraphy for the Santonian/Campanian boundary interval, the Kurdistan Region, northeast Iraq

The first high-resolution integrated biostratigraphic study for Santonian/Campanian sediments of the Tabin section in the Kurdistan Region, northeast Iraq is provided. The study, based on 28 closely spaced samples, combines data from planktic foraminifers (25 species), calcareous nannofossils (32 species) and two ammonite genera in the Kometan Formation, marking the Santonian/Campanian boundary (S/C boundary) in the Kurdistan Region. In the absence of the crinoid Marsupites testudinarius, the proposed boundary marker, secondary markers such as calcareous nannofossils, planktic foraminifers and ammonites, have been used to establish a multi-stratigraphic biozonation for the late Santonian–early Campanian duration. Based on the occurrences of calcareous nannofossils, three biozones are identified — Lucianorhabdus cayeuxii (late Santonian), Calculites obscurus (latest Santonian–earliest Campanian), and Broinsonia parca parca (early Campanian). Seven calcareous nannofossil bioevents and three planktic foraminiferal bioevents are also identified. The Santonian/Campanian boundary is marked by: (a) the LO (Last Occurrence) of the planktic foraminifera D. asymetrica, (b) the FOs (First Occurrence) of the calcareous nannofossil species B. parca parca and B. parca constricta, (c) the extinction of several planktic foraminiferal species of Dicarinella and Marginotruncana, (d) the abundance and diversification of the planktic foraminifera genera, Globotruncana and Globotruncanita at the beginning of the Campanian, and (e) the disappearance of the ammonite genus Texanites, 0.5 m below (i.e., at 19 m) the disappearance of all Dicarinella and Marginotruncana species in the study section. Similar to several other Tethyan sections, the FO of B. parca parca is above the LOs of D. concavata and D. asymetrica; the LO of D. asymetrica is used here to mark the S/C boundary

Determining the habitat depth of the planktic foraminifera Dentoglobigerina altispira in the eastern Arabian Sea during the middle Miocene

Tests of planktic foraminifera are important tracers for reconstructing past oceanic environments. It is essential to have accurate information of the habitat depth of the planktic foraminiferal species whose isotopic and elemental signatures are being used to infer past climatic and oceanographic conditions. The planktic foraminifera species Dentoglobigerina altispira is a very common component of Miocene and Pliocene tropical to warm subtropical planktic foraminiferal assemblages but different findings exist about the habitat depth of this species from shallow to deep water. For that reason, comparative stable carbon and oxygen isotope analyses of four coexisting planktic foraminifera species from National Gas Hydrate Program Expedition Site 01 (Site NGHP-01-01A) were performed in order to reconstruct the habitat depth of D. altispira in the eastern Arabian Sea for the middle Miocene (~16–12.5 Ma). The D. altispira oxygen isotope values are on average higher than those of the shallow water reference species Trilobatus sacculifer and Globigerinoides obliquus, but still significantly lower than those for the deeper dwelling species Dentoglobigerina venezuelana. This suggests that D. altispira inhabited a deeper habitat depth than the estimated habitat depth for modern T. sacculifer in the eastern Indian Ocean (~50 m). Paired D. altispira and T. sacculifer Mg/Ca data reveal lower Mg/Ca and thus colder temperatures for D. altispira than for T. sacculifer, also suggesting that D. altispira calcified at a greater water depth than T. sacculifer. The data of this study suggest that D. altispira inhabited the lower mixed layer and/or upper thermocline in the eastern Arabian Sea during the middle Miocene.

Two-Tiered Transition of the North Atlantic Surface Hydrology during the Past 1.6 Ma: Multiproxy Evidence from Planktic Foraminifera

Analyses of planktic foraminiferal assemblage data, test morphology, and stable oxygen isotopes from the Integrated Ocean Drilling Program (IODP) Site U1304 in the North Atlantic reveal a stepwise regional migration of the oceanic fronts around 0.6 Ma and 0.4 Ma, i.e., during Marine Isotope Stages (MISs) 15 and 11, respectively. Both changes of planktic foraminiferal assemblages and shell carbonate isotopes indicate that the cold Arctic waters in general persisted at IODP Site U1304 from 1.6 to 0.6 Ma (MIS 15), even though the warmer waters originating from the Atlantic waters episodically bathed Site U1304 during the interglacial periods. During the time-interval from ca. 0.6 to 0.4 Ma (MISs 15–11), an alternating dominance of Artic and Atlantic waters at the Site U1304 has been suggested from isotopic evidence. In MIS 11, the dominant planktic foraminiferal species Neogloboquadrina pachyderma experienced a short-term but significant decrease in test size. The test-size change may have been caused by accelerated reproduction in more favorite feeding conditions over the long-lasting interglacial period around the Subarctic Front. This finding is supported by the presence of massive diatoms oozes in the same time-interval. The modern-type glacial/interglacial change of the surface water system established since ca. 0.4 Ma (MIS 11) followed the Mid-Brunhes Event.

Contribution of foraminifers in biostratigraphy and paleoecology interpretations of the basal Eocene from the phosphatic Sra Ouertaine basin, in the southern Tethys(Tunisia)

Micropaleontological, sedimentological and statistical studies were carried out on the late Paleocene-early Eocene succession of Sra Ouertaine and Dyr El Kef in Northern open phosphatic Basin of Tunisia. Based on the abundance and stratigraphic distribution of planktic foraminiferal species, five planktic zones have been recognized from the base to the top of the phosphatic layers. The El Acarinina sibaiyaensis Zone, the E2 Pseudohastigerina wilcoxensis Zone, the E3 Morozovella marginodentata Zone, the E4 Morozovella formosa Zones and the E5 Morozovella subbotinae Zone. The placement of Paleocene-Eocene boundary (PETM) is just below the base of the phosphatic interval. The ETM-2 event may be detectable in the analyzed biotic record of Sra Ouertaine.Based on benthic assemblages, abundances, cluster and multivariate statistical analyses, two biofacies were recognized for each section. The recognized ecozones are typical of warm and shallow water inner neritic setting (dominance of epifaunal fauna Anomalinoides, Dentalina and Cibicidoides associated with Frondicularia phosphatica, Trochamminoides globigeriniformis and Eponides elevatus). The paleoenvironment is eutrophic (presence of several bolivinitids and verneuilinids). For the Dyr El Kef section and P5 and E2 of Sra Ouertaine section, our records indicate that paleoenvironment is influenced by coastal upwelling without oxygen-deficiency, the paleodepth is estimated to be around 50 m. The paleoecosystem is diversified and balanced with a general tendency to stressed condition. While the upper part of Sra Ouertaine section is more eutrophic, influenced by coastal upwelling with oxygen-deficiency, the paleodepth is estimated to be less than 50 m and the ecosystem is unsettled.

Planktic foraminiferal changes in the western Mediterranean Anthropocene

The increase in anthropogenic induced warming over the last two centuries is impacting marine environment. Planktic foraminifera are a globally distributed calcifying marine zooplankton responding sensitively to changes in sea surface temperatures and interacting with the food web structure. Here, we study two high resolution multicore records from two western Mediterranean Sea regions (Alboran and Balearic basins), areas highly affected by both natural climate change and anthropogenic warming. Cores cover the time interval from the Medieval Climate Anomaly to present. Reconstructed sea surface temperatures are in good agreement with other results, tracing temperature changes through the Common Era (CE) and show a clear warming emergence at about 1850 CE. Both cores show opposite abundance fluctuations of planktic foraminiferal species ( Globigerina bulloides , Globorotalia inflata and Globorotalia truncatulinoides), a common group of marine calcifying zooplankton. The relative abundance changes of Globorotalia truncatulinoides plus Globorotalia inflata describe the intensity of deep winter mixing in the Balearic basin. In the Alboran Sea, Globigerina bulloides and Globorotalia inflata instead respond to local upwelling dynamics. In the pre-industrial era, changes in planktic foraminiferal productivity and species composition can be explained mainly by the natural variability of the North Atlantic Oscillation, and, to a lesser extent, by the Atlantic Multidecadal Oscillation. In the industrial era, starting from about 1800 CE, this variability is affected by anthropogenic surface warming, leading to enhanced vertical stratification of the upper water column, and resulting in a decrease of surface productivity at both sites. We found that natural planktic foraminiferal population dynamics in the western Mediterranean is already altered by enhanced anthropogenic impact in the industrial era, suggesting that in this region natural cycles are being overprinted by human influences. • Western Mediterranean planktic foraminifera and sea surface temperature records. • Planktic foraminiferal changes explained by natural variability in pre-industrial times. • Anthropogenic warming depletes marine surface production.

Paleoceanographic turnovers during the Plio-Pleistocene in the southeastern Indian Ocean: Linkages with Northern Hemisphere glaciation and Indian Monsoon variability

Earth experienced warm temperatures during the Pliocene followed by a substantial cooling that culminated in an ice age climate at the beginning of the Pleistocene. This warmth had a significant impact on global environments and ocean circulation. The collision of the Indian and Eurasian plates further amplified this climatic pattern. The southern Indian Ocean was severely impacted by these changes in ocean circulation and climatic pattern during the Plio-Pleistocene. We reconstruct paleoceanographic turnovers in the southeastern Indian Ocean during the Plio-Pleistocene using benthic foraminiferal assemblages from ODP Sites 752 and 757, combined with relative abundances of selected planktic foraminiferal species and stable isotope ratios (δ18O and δ13C) of surface-dwelling and thermocline planktic foraminifera from Site 757. The influence of southern source Antarctic Intermediate Water (AAIW) since 4.5 Ma is marked by fluctuations in productivity till the intensification of the Northern Hemisphere glaciation (NHG) at ~3 Ma. Our isotopic data provide no evidence for cooling during the 4–3 Ma interval either for upper (Gs. ruber) or lower (M. menardii) mixed-layer waters, at a time when a switch in the source of the Indonesian Throughflow may have occurred. The increased mixed-layer species abundances since 4 Ma suggest oligotrophic conditions at low-latitude Site 757 due to thick mixed-layer coinciding with the constriction of the Indonesian Gateway and intensification of the NHG. The intensification of the NHG and monsoon seasonality caused an enhanced inflow of AAIW in the southeastern Indian Ocean since ~2.5 Ma.