Benthic Foraminifera Research Articles

Stratigraphic Analysis and Depositional Environment of the Newly Recorded Umm Er Rhadhuma Formation (Paleocene) from the Borehole K.H12/7, South Anah City, Western Iraq

The Paleocene benthic foraminiferal zonation of the Umm Er Rhadhuma Formation from the borehole (K.H 12/7), South Anah City (Western Iraq), has been re-studied and re-analyzed precisely based on the large benthic foraminifera (LBF). They are represented by two biozone Rotorbinella hensoni Partial Range Zone, recorded from the Lower and middle parts of the Umm Er Rhadhuma Formation and Lockhartia praehaimei Partial Range Zone determined Uppermost of this unit, and dated to be the Selandian – Thanetian stage. Almost all the biogenic (micro and macro) and non-biogenic constituents, including large benthic foraminifera, Algae, Echinoderm, Bryozoans, Oyster, Gastropod fragments, and peloids, in addition to lithofacies types, indicate that this succession belongs to the Umm Er Rhadhuma Formation. Furthermore, the Paleocene shallowing upwards succession is recognized from seven identified microfacies (MF1 to MF7), which suggests three significant facies associations. A broad inner ramp represents them and is warm shallow open normal marine water (FA1). In contrast, the second facies association represents by the predominated bioclastic sand shoal facies association (FA2) and finally reaches the semi-restricted lagoon facies associations (FA3). The interaction between the local tectonic disturbance along Rutba high and eustatic sea level mainly controls the development of two sequence boundaries of Type-1 (SB1) that occurred respectively at the Cretaceous /Palaeogene K- Pg boundary and Paleocene /Eocene boundary. The Paleocene depositional system starts with major transgression during the Selandian above a sequence boundary of type one (SB.1), that separates the Late Cretaceous (Maastrichtian) successions of the Tayarat Formation from the overlying Paleocene succession with a significant gap, covering the whole Danian age (That is the top of Tectonic Megasequence AP. 9). The predominance of retrogradation staking tract indicated the transgressive system tract during the late Selandian and early Thanetian as a result of an increase in the sea level rise and expanded accommodation space. The highstand system tracts show aggradational and then change to a progradational stacking pattern by the end of the Thanetian and mark significant sea level drawdown with a new sequence boundary of type one between them.

New evidence for Early Miocene palaeoenvironmental changes in the North Croatian Basin: Insights implicated by microfossil assemblages

An integrated stratigraphic study has been performed of the Lower Miocene deposits of the Poljanska and Mala sections (North Croatian Basin), coupled with 40Ar/39Ar dating, geochemical and mineralogical study of tuffitic and silty sand beds. The sedimentary record evidences deposition influenced by volcaniclastic input. The presence of marine, brackish and non–marine microfossils indicates complex palaeoenvironment, palaeoecology, and palaeobiogeography. Four different units were recognized based on their fossil content and sedimentological data. At the base of the Poljanska section (Unit P1), tuffitic sediments bear common endemic brackish, and rare marine to freshwater and terrestrial microfossils. Radiometric 40Ar/39Ar dating obtained on volcanic glass shards from this layer provided an age of 22.2 ± 1.9 Ma correlating with the earliest Early Miocene and indicating the existence of older volcanic activity in the NCB pro tempore. The succession transitions into the brackish-water lacustrine environments (Unit P2). This unit has two presumed different climatic events: a maximum temperature event in the lower part of the interval and one interruption with lower temperatures recognized in the upper part of the interval. The co-occurrence of limnic and marine species in the uppermost part of the investigated sediments (Unit P3) indicates a marine inflow into the coastal lake. It marks the beginning of a salina-type lake formation in Poljanska. In the Mala section (Unit M1), biostratigraphically dated to the NN4 Zone, a transgressive sequence is documented through the presence of marine calcareous nannoplankton, planktonic and benthic foraminifera, and ostracods.

Paleoenvironmental significance of benthic foraminiferal associations of the Hauterivian to Barremian marine beds of the Neuquén Basin, Patagonia, Argentina

The upper Hauterivian-lower Barremian sedimentary sequences of the Agua de la Mula Member of the Agrio Formation (Neuquén Basin, Argentina) represent shallow marine environments characterized by mixed siliciclastic‑carbonate deposition. Ten benthic foraminiferal associations based on species composition were defined and evaluated in relation to explanatory variables such as facies, sequence stratigraphy, location and age. Variations in sedimentation rates, food and oxygen availability related to relative sea-level changes largely control distribution of the benthic foraminiferal associations. Four associations (Guttulina sp., Polymorphinids, Spiroplectammina sp.2-Haplophragmoides sp.1, and Planularia madagascariensis) are mostly composed by shallow infaunal, bacterial and detritivorous foraminiferal scavengers that largely occur in sandy facies within 3rd-order regressive systems tracts. These associations are thought to be indicative of well oxygenated and organic matter-rich sediments below the sediment-water interface. The remaining six associations consist of epifaunal, mainly opportunistic foraminifera with active herbivorous and detritivorous trophic strategies. Among them, Epistomina hechti - Epistomina australis and Reinholdella hofkeri associations occur in fine-grained, dark shales throughout 3rd-order transgressive systems tracts, and are considered related to oxygen and food stressed environment. An integrated approach, using benthic foraminifera (alpha diversity analysis, epifaunal/infaunal ratio) and multivariate statistical methods (cluster analysis, RDA, partial-RDA, PERMANOVA, PCoA), allowed to evaluate the paleosynecological significance of benthic associations, and to relate certain paleoenvironmental settings to relative sea-level changes recorded in the Agua de la Mula Member. The application of foraminiferal associations analysis in the paleoenvironmental interpretations led to recognize the influence of major relative sea-level changes in shaping higher-frequency sequences for this sector of the Neuquén Basin. Such approach can also be applied to other sectors of the basin and to high-frequency sedimentary sequences of comparable shallow marine settings.

Monitoring marine oxygen with pores in benthic foraminifera

Monitoring marine oxygen with pores in benthic foraminifera

Paleoenvironments and stratigraphy of the Valanginian–Hauterivian carbonates of the Arabian Platform: Implications for the recognition of the Weissert Event on the Southern Tethys

On the Arabian Platform, the Valanginian Weissert Event is associated with the sudden drowning of a major north-easterly prograding carbonate platform located on the southern margin of the Tethys Ocean. This was associated with a sharp back-stepping of the main facies belts to the south-west, bringing shallow marine carbonates into the previously restricted platform top. Integrated detailed facies analysis, biostratigraphy (including nannofossil and palynology) and carbon isotopes have been used to reconstruct the evolution of the carbonate shelf during the Valanginian–Hauterivian in Saudi Arabia. During the early Valanginian the study area was dominated by the deposition of dolomitized clay-prone microbial intertidal mudstones, which passed basinwards into low-energy inner ramp limestones. These facies encompass the initial stage of a 3rd order transgressive trend above the regional Lower Valanginian Unconformity. They are sharply overlain by Lithocodium/Bacinella-dominated floatstones, indicating the maximum flooding of the platform during the late Valanginian. These deposits systematically increase in thickness and abundance towards the platform margin and are associated with a broad positive excursion in δ13C (c.+2‰ V-PDB), corresponding to the Weissert Event. The presence of abundant Lithocodium/Bacinella in strata deposited during the major flooding of the platform is consistent with higher nutrient levels and increased upwelling during the late Valanginian. The Valanginian–Hauterivian boundary is marked by a regional unconformity identified through palynology and benthic foraminifera assemblages, and locally confirmed by carbon isotopes. The combination of carbon isotope data with detailed palynology and micropaleontology provided a stratigraphic resolution in line with ammonite biozones published in the western Tethys. The Valanginian–Hauterivian continental palynoflora, described for the first time on the Arabian Platform, is dominated by primitive conifer pollen such as Classopollis suggesting a rather arid climate in agreement with published reconstructions. In addition, the occurrence of various fern and bryophyte spores suggests an increase in humidity along coastline areas, associated with higher continental input into inner ramp settings, therefore affecting the carbonate factory.

Late Barremian–Aptian paleoenvironmental variations and OAE1a environmental effect in the eastern Crimea

The early Aptian Oceanic Anoxic Event 1a (OAE1a, or Selli Event) is widely known from many oceanic and inland sections as an interval of enhanced accumulation of sediments rich in total organic carbon (TOC), associated with the turnover in the global carbon budget and dramatic biotic variations. Our multidisciplinary study of the upper Barremian to lower upper Aptian deposits from the eastern part of Crimean Peninsula allowed us to confirm the presence of a layer that correlates to OAE1a and revealed significant reorganization in the planktonic and benthic foraminifera, nannofossils, ostracod and terrestrial plant communities at this level. The low-calcareous OAE1a deposits from the eastern Crimea lack in TOC that is not typical sedimentological response to this critical event. The OAE1a onset was associated with a nannoconid crisis, occurrence of low-abundance Hedbergella planktonic foraminifera, increased abundance of benthic foraminifera and ostracods and the bloom of Classopolis on the adjacent land. The calcareous microplankton biota was highly oppressed during OAE1a up to total elimination in the core of the event. Benthic assemblages indicate the occurrence of dysoxic conditions at the sea-floor. The absence of organic matter in the deposits of the OAE1a interval points to the low basinal biotic productivity and low input of terrestrial organic matter. We suggest that oligotrophication of the basin was related to the transgressive pulse, which led to small-scale landward moving of the coastal line barriered by coastal highland. The hot arid climatic conditions indicated by terrestrial plants, prevented the supply of nutrients and terrestrial organic matter into the basin that caused low algal and bacterial productivity and prevented accumulation of TOC-rich sediments. The termination of OAE1a coincides with the occurrence of warm humid climate and erosion of ephemeral coastal highland, more likely, built up by soft clayey sediments. The transit restoration of the normal marine biota in the early late Aptian was interrupted in the middle late Aptian by new long-lived regression led to enhanced terrestrial runoff and, possibly, fresh water input killed marine biota and caused the accumulation of low-calcareous clay.

Modern biogeography of benthic foraminifera in an urbanized tropical marine ecosystem

Abstract We investigated the biogeography of benthic foraminifera in a highly urbanized tropical seascape, i.e. Hong Kong, in order to assess their utility as bioindicators relative to other marine fauna. Hong Kong is one of the largest coastal cities on the planet and studies of other benthic fauna in the region are available for comparison. We found that: (1) turbid, muddy habitats host a unique foraminiferal fauna; (2) areas with intermediate levels of eutrophication have the highest foraminiferal species diversity; (3) semi-enclosed and heavily polluted environments host a distinct foraminiferal fauna, characterized by low taxonomic diversity and/or high dominance, and that is acclimated to stressful marine conditions. Biodiversity patterns of foraminifera in Hong Kong are generally consistent with those of other soft-sediment macro- and meio-fauna (e.g. polychaetes, molluscs and ostracods); however, foraminifera may be more sensitive than these other groups to eutrophication and associated changes in coastal food webs. The tolerance of some, but not other, species to eutrophic and hypoxic conditions means that foraminiferal faunas can serve as bioindicators across a wide array of environmental conditions, in contrast with corals whose sensitivity to eutrophication results in their absence from eutrophied settings. The well-known autoecology of foraminifera taxa can help to characterize environmental conditions of different habitats and regional environmental gradients. Although the use of fauna as bioindicators may be most robust when data are compared for multiple taxonomic groups, when such broad sampling is not available, benthic foraminifera are particularly well suited for environmental assessments due to their ubiquity, interspecific environmental breadth, and the well-understood environmental preference of individual taxa.

Benthic foraminiferal morphogroups at the end-Guadalupian extinction in eastern Sichuan Basin, China

Benthic foraminiferal morphogroups near the Permian Guadalupian-Lopingian (GLB) reveal their responses to palaeoenvironmental and palaeoecological changes in the eastern Sichuan Basin, China. According to the shell forms, coiling modes, and life positions linked to the life styles and feeding strategies, seven types of benthic foraminiferal morphogroups were recognized in Guadalupian and lower Wuchiapingian carbonate rocks from four lithological profiles. During the Guadalupian Epoch, highly diversified and large number of benthic foraminifera and their various feeding strategies indicated sufficient trophic resources for food. However, the foraminiferal assemblages dropped dramatically after the end-Guadalupian extinction event, reflecting remarkable changes in the nutrient sources and oxygen conditions in the ocean. In the early Wuchiapingian Epoch, nutrient input and plant debris decreased rapidly, while terrigenous detritus increased. As a result, the number of herbivores significantly declined, and suspension feeders and detritivores dominated. Changes in foraminiferal morphogroups in the eastern Sichuan Basin confirmed the existence of a end-Guadalupian extinction event. Surviving benthic foraminifera in Wuchiapiangian, such as Codonofusiella and Eotuberitina, prefer epiphytism, multiple feeding strategies, and low oxygen concentrations, which helped them sustain in a severe ecological environment. The dominant Wuchiapingian foraminifera has changed to other genera, which had to alter their living habits by enlarging the bottom contact area to resist waves and expanding semi-shells to increase feeding capacity. Benthic foraminiferal assemblages from adjacent regions (south China, Tibet, Iran, and Greece) were consistent with our investigation of the morphogroups and showed a similar response to the end-Guadalupian extinction event.

Five million years of life history record in an uppermost Cretaceous northern Tethyan marine succession, Eastern Carpathians (Romania): Microfossil content and palaeoenvironmental assessment

New biostratigraphic investigations based on palynomorphs (mainly dinoflagellate cysts), foraminifera and calcareous nannoplankton recovered from eight geological sections indicate that the Hangu Formation near the Pluton-Pipirig area (Tarcău Nappe, Eastern Carpathians, Romania), previously assigned to the Senonian–Paleocene interval, includes only uppermost Cretaceous deposits. The palynological assemblages are moderately rich, with a total of 167 well-preserved taxa. The marine palynomorphs – essentially consisting of dinoflagellate cysts (dinocysts) – are dominated by peridinioid taxa, mainly recorded in upper Upper Campanian–lower Maastrichtian deposits, and by a high-diversity assemblage of gonyaulacoid taxa during the late Maastrichtian. Marine algae and dinogymnioid dinocysts were less common. The terrestrial palynoflora is dominated by fern spores and angiosperm pollen, with subordinate gymnosperm pollen. The foraminiferal assemblages include an assortment of well-preserved agglutinated forms, present mainly in the upper Maastrichtian deposits, whereas calcareous benthics and planktonic foraminifera are rare and poorly preserved. Calcareous nannoplankton assemblages are also rare, often represented by two taxa (Micula staurophora and Watznaueria barnesiae); certain important biostratigraphic markers were found to be reworked in the analyzed deposits. Age assignments for the studied sections were mainly provided by dinocysts, through the identification of significant marker taxa and comparisons with well-calibrated Campanian–Maastrichtian dinocyst assemblages from well-dated sections and stratotypes, located mostly in the Northern Hemisphere.Indices such as particulate organic matter (POM) composition, the relative abundance of dinocyst eco-groups, as well as agglutinated foraminiferal morphogroups, were used to reconstruct the depositional environments of the Hangu Formation from the studied area. The upper Upper Campanian–lower Maastrichtian deposits from the Pluton-Pipirig sections were mainly deposited in neritic marine conditions, although occasional redeposition of the sediments transported by turbidity currents towards deeper water settings is not excluded, either. The depositional environments evolve towards outer neritic to distal (bathyal) during the late Maastrichtian, as indicated by palynofacies constituents and by high frequencies of gonyaulacoid dinocysts and deep-water benthic foraminifera.

Paleocene-Eocene foraminifera from the Tuz Gölü Basin (Salt Lake Basin, Central Türkiye) and their paleoenvironmental interpretations

Paleocene-Eocene aged sediments from the east of Tuz Gölü Basin (Central Türkiye) provide significant data for foraminifera contents and their paleoenvironmental clues. They are important in revealing the stratigraphy of the region and the Paleocene-Eocene geological history of Türkiye. The sediments, composed mainly of carbonates, are known as KarapınaryaylasıFormation. In this formation, benthic foraminifera representing SBZ2 to SBZ12 biozones corresponding to the Selandian-Late Cuisian time interval were identified in ten measured stratigraphical sections. The zonal interval from the E7 Zone (late Ypresian) to the E10 Zone (Lutetian) is characterized by the marker species of planktonic foraminifera defined in the clayey limestones from the uppermost part.The studied formation is divided into four main facies and eleven sub-microfacies types. The clayey limestone levels of the KarapınaryaylasıFormation, which generally starts with a transgressive sequence, contain abundant planktonic foraminifers, while the lithologies of grainstone, packstone and wackestone are rich in benthic foraminifers. Benthic foraminifer assemblages indicate different paleoenvironments from lagoon to back-bank, bank and fore-bank. The obtained foraminiferal data show the Selandian-Lutetian age range and various paleoenvironments from the lagoon to the open sea.

A 1.5-million-year record of orbital and millennial climate variability in the North Atlantic

Abstract. Climate during the last glacial period was marked by abrupt instability on millennial timescales that included large swings of temperature in and around Greenland (Daansgard–Oeschger events) and smaller, more gradual changes in Antarctica (AIM events). Less is known about the existence and nature of similar variability during older glacial periods, especially during the early Pleistocene when glacial cycles were dominantly occurring at 41 kyr intervals compared to the much longer and deeper glaciations of the more recent period. Here, we report a continuous millennially resolved record of stable isotopes of planktic and benthic foraminifera at IODP Site U1385 (the “Shackleton Site”) from the southwestern Iberian margin for the last 1.5 million years, which includes the Middle Pleistocene Transition (MPT). Our results demonstrate that millennial climate variability (MCV) was a persistent feature of glacial climate, both before and after the MPT. Prior to 1.2 Ma in the early Pleistocene, the amplitude of MCV was modulated by the 41 kyr obliquity cycle and increased when axial tilt dropped below 23.5∘ and benthic δ18O exceeded ∼3.8 ‰ (corrected to Uvigerina), indicating a threshold response to orbital forcing. Afterwards, MCV became focused mainly on the transitions into and out of glacial states (i.e. inceptions and terminations) and during times of intermediate ice volume. After 1.2 Ma, obliquity continued to play a role in modulating the amplitude of MCV, especially during times of glacial inceptions, which are always associated with declining obliquity. A non-linear role for obliquity is also indicated by the appearance of multiples (82, 123 kyr) and combination tones (28 kyr) of the 41 kyr cycle. Near the end of the MPT (∼0.65 Ma), obliquity modulation of MCV amplitude wanes as quasi-periodic 100 kyr and precession power increase, coinciding with the growth of oversized ice sheets on North America and the appearance of Heinrich layers in North Atlantic sediments. Whereas the planktic δ18O of Site U1385 shows a strong resemblance to Greenland temperature and atmospheric methane (i.e. Northern Hemisphere climate), millennial changes in benthic δ18O closely follow the temperature history of Antarctica for the past 800 kyr. The phasing of millennial planktic and benthic δ18O variation is similar to that observed for MIS 3 throughout much of the record, which has been suggested to mimic the signature of the bipolar seesaw – i.e. an interhemispheric asymmetry between the timing of cooling in Antarctica and warming in Greenland. The Iberian margin isotopic record suggests that bipolar asymmetry was a robust feature of interhemispheric glacial climate variations for at least the past 1.5 Ma despite changing glacial boundary conditions. A strong correlation exists between millennial increases in planktic δ18O (cooling) and decreases in benthic δ13C, indicating that millennial variations in North Atlantic surface temperature are mirrored by changes in deep-water circulation and remineralization of carbon in the abyssal ocean. We find strong evidence that climate variability on millennial and orbital scales is coupled across different timescales and interacts in both directions, which may be important for linking internal climate dynamics and external astronomical forcing.

Indian margin methane hydrate dissociation recorded in the carbon isotopes of benthic (Miliolida) foraminifera

Methane hydrates in ocean sediments have been investigated across various timescales using a broad array of indicators to better understand hydrate dynamics and climate linkages. Here we report individual benthic and planktonic foraminiferal isotopic analyses at three sites from distinct oceanic environments in the northern Indian Ocean. The multi-species, multi-site analyses identify a unique δ13C response in Miliolida benthic foraminifera Pyrgo spp., Quinqueloculina spp., and Spiroloculina spp. suggesting that some species within these genera record the location and timing of past methane hydrate dissociation in the stable carbon isotopic composition of their skeletal (test) material. Our results document that dissociation occurred in the Mahanadi offshore basin, northwest Bay of Bengal, during glacial, transitional, and interglacial intervals of the past 1.5 million years. More negative test δ13C coupled with more positive δ18O supports the inference of interglacial-age dissociation, likely driven by increased intermediate water temperatures.

NEOKILIANINA CONCAVA RAMALHO, 2015 AND NEOKILIANINA RAHONENSIS (FOURY & VINCENT, 1967): A DIMORPHIC PAIR OF UPPER JURASSIC LARGER BENTHIC FORAMINIFERA?

The species Neokilianina concava Ramalho was described from the Kimmeridgian of Portugal found in the same (isochronous) levels as Neokilianina rahonensis (Foury & Vincent). The external morphology was indicated as the only difference between the two taxa, notably a pronounced concavity in the middle part of the cone base and a wider apical angle in N. concava against N. rahonensis. These differences can reasonably be considered as intraspe-cific variations, reflecting adult test dimorphism between the megalospheric (N. rahonensis) and microspheric specimens (N. concava), also suggested by their isochronous occurrence. The morphological features that were used for species discrimination are well recorded from the two generations (A-, B-forms) of other larger benthic foraminifera including the Orbitolinidae.

Upper Jurassic to Lower Cretaceous benthic foraminifera from South Tibet (Tethyan Himalayas): systematic, biostratigraphic, and palaeoecologic implications

The present study represents the first attempt to described foraminiferal fauna of the Gucuo Locality and is among the first work to illustrate the Upper Jurassic to Lower Cretaceous benthic foraminifers of South Tibet. The material consists in a combination of unpublished data on the Gucuo Section and published data on the Gyangze; Weimei, and Bandingsi sections.A total of 239 specimens have been currently recorded in the Upper Jurassic to Lower Cretaceous Menkadun and Gucuo formations of the Gucuo locality. To facilitate further researches on foraminifers from the Tethyan Himalayas, a total of 59 species from 38 genera have currently been repertory and described. Among the recorded specimens, a few species are significant biostratigraphic markers used to identify and constrain the age of four foraminiferal assemblages. The Textularia aff. haeusleri assemblage contains a few numbers of agglutinated species very similar to the one described in the Oxfordian to Kimmeridgian Nupra Formation of the Thakkola Region. The Tithonian Trochammina quinqueloba assemblage is a widespread biostratigraphic horizon recorded in both southern and northern parts of South Tibet, as well as in the Indian and the Proto-Atlantic oceans. The Berriasian to Valanginian Trochammina abrupta assemblage contains typical Early Cretaceous foraminifers. It confirms the Jurassic/Cretaceous boundary should be delineated at the base of the shale Unit of the Gucuo Formation, although it was previously attributed to the base of the volcaniclastic sandstone units using ammonite data. This latest being currently associated to the Valanginian to Hauterivian Ammobaculites crepinae–Textularia bettenstaedti foraminiferal assemblage.A palaeoecological reconstruction along a southwest to northeast transect of South Tibet, Himalayas, is proposed to understand the composition and dynamic of foraminiferal assemblages along with palaeoenvironmental changes. The morphogroup approach has been selected as the best methods to illustrate both sea-level and oxic changes. The northern tectonic zone of South Tibet is associated with the abundance of deep-water agglutinated foraminifers, which suggests a deep environment beyond the shelf break. The southern tectonic zone of South Tibet is rich in typical species of shallow environment and was located on the neritic shelf. The morphogroup analysis reveals localized, periodic disaerobic conditions on the sea-floor. The Jurassic to Cretaceous Boundary interval was associated with a drop of the sea-level, whereas the rise in diversity and abundance of marginal-sea taxa during the Valanginian to Hauterivian times underline a higher sea-level and a pulse in the development of epeiric seas in the southern part of South Tibet.

A global synthesis of high-resolution stable isotope data from benthic foraminifera of the last deglaciation

We present the first version of the Ocean Circulation and Carbon Cycling (OC3) working group database, of oxygen and carbon stable isotope ratios from benthic foraminifera in deep ocean sediment cores from the Last Glacial Maximum (LGM, 23-19 ky) to the Holocene (<10 ky) with a particular focus on the early last deglaciation (19-15 ky BP). It includes 287 globally distributed coring sites, with metadata, isotopic and chronostratigraphic information, and age models. A quality check was performed for all data and age models, and sites with at least millennial resolution were preferred. Deep water mass structure as well as differences between the early deglaciation and LGM are captured by the data, even though its coverage is still sparse in many regions. We find high correlations among time series calculated with different age models at sites that allow such analysis. The database provides a useful dynamical approach to map physical and biogeochemical changes of the ocean throughout the last deglaciation.

Benthic Foraminifera Diversity of the Abyssal Northwest Atlantic

The species diversity of benthic foraminifera at four abyssal working areas in the Labrador Sea, Labrador Basin, and Southwest of the Azores is documented. One hundred and fifty taxa (forty-three not assigned to a species) were found and their diversity was recorded. One hundred and twenty-four taxa (fifteen not assigned to a species) were illustrated with optical and/or SEM (Scanning Electron Microscope) images on twelve plates. The material was sampled during RV Sonne cruise SO286 as part of IceDivA2 (Icelandic marine Animals meets Diversity along latitudinal gradients in the deep sea of the Atlantic Ocean 2). IceDivA2 investigated the biodiversity within key groups of the marine benthic abyssal habitats of the North Atlantic. Thirty-two samples from four sliced and three full cores, from six stations sampled with a MUC (Multiple corer), were analyzed. Given low sedimentation rates in such environments the material is assumed to be of Holocene to late Pleistocene age. Due to the scarcity of living specimens this study was based on total assemblages. Four species-based clusters are identified, which correspond to the four working areas. The samples of each cluster show specific characteristics markedly different from those of the samples of the other clusters. It indicates that abyssal faunas are heterogeneous. Three clusters are dominated by Epistominella exigua (Brady, 1884), which is recorded as not rare to dominant in many abyssal plains worldwide. The faunal differences are manifested in the long tail of less important species and differing abundances of E. exigua.

The fossil assemblage from Pontils, a middle Eocene primate-bearing locality from Northeastern Spain

ABSTRACT The Pontils fossil site (middle Eocene, Ebro Basin, Spain) includes several vertebrate-bearing levels situated in a sequence recording a continental to marine transition. Although the locality has been known since the 1980s and scarce mammal remains have been already documented, an intensive sampling has not been developed until now. This work presents the first results of the recent field campaigns carried out at this site. Seven levels have yielded significant vertebrate remains, revealing a diverse assemblage which includes chondrichthyans, actinopterygians, amphibians, crocodilians, squamates, metatherians, eulipotyphlans, apatotherians, chiropterans, rodents, artiodactyls, perissodactyls, and primates, besides other non-vertebrate fossils. The Pontils assemblage indicates a mangrove swamp environment with warm and humid conditions and increasing marine influence towards the top of the sequence. Among mammals, primates are particularly diverse, including abundant remains of a minuscule, still undetermined omomyiform, and scarce teeth of Pseudoloris, Necrolemur, and an undetermined anchomomyin. The occurrence of larger benthic foraminifera allows the assignment of Pontils to Shallow Benthic Zone 17 (Bartonian), solving the debate about the age of the locality, previously assigned either to the Bartonian or the Lutetian. These data, together with previous magnetostratigraphic analyses, allow correlation to chrons C18r or C18n.1r, constraining the age of Pontils to between 39.58 and 41 Ma. Therefore, the Pontils site represents a new reference section for the correlation of marine and continental biostratigraphy during the middle Eocene.

Radiocarbon evidence for reduced deep water ventilation of the northern Indian Ocean during the last glacial maxima and early deglaciation

Enhanced outgassing of sequestered carbon to the atmosphere by upwelling of deep water in the Southern Ocean during the last deglaciation is assumed to be the main factor that modulated changes in atmospheric CO2 and atmospheric radiocarbon activity; however, the exact mechanism behind this deglacial CO2 release still remains unclear. In this study, we have investigated ventilation changes in the deep waters of the northern Indian Ocean over the past 25 kyr BP using paired benthic and planktic foraminiferal radiocarbon, along with stable carbon and oxygen isotopes of benthic foraminifera, sedimentary CaCO3 content, and coarse fraction from the gravity core SSD-044/GC-01 (3160 m water depth) collected from Central Equatorial Indian Ocean. The results indicate a greater proportion of southern sourced CO2-rich, poorly-ventilated Antarctic Bottom Water (AABW) during the Last Glacial Maximum (LGM) and Heinrich Stadial (HS1), in the northern Indian Ocean. The observed poor ventilation during the last glaciation shows that the northern Indian Ocean was a part of the glacial ocean aged carbon pool. Improved ventilation during the Bølling-Allerød (B-A) is consistent with the rapid resumption of Atlantic overturning circulation and inflow of North Atlantic Deep Water (NADW) into the northern Indian Ocean at the onset of the B-A, which caused flushing of the deep-carbon pool with evidence of degassing from the northern Indian Ocean. This study thus supports the role of Southern Ocean in modulating atmospheric CO2 variations during the last deglaciation.

Foraminifera dissolution phases in the upper cretaceous succession of Jebel Duwi, Egypt

The present work examines the function of differential dissolution in planktic and benthic foraminifera and introduces the major factors that affect dissolution in early Mid-Maastrichtian Event MME and Late Maastrichtian Event LME paleoenvironmental reconstructions. Two observations on foraminifera dissolution in the Dakhla Formation, where planktic foraminifera are more susceptible to dissolution than benthic foraminifera in the Hamama Member of the Jebel Duwi section, Eastern Desert (Egypt). They are characterized by a decline in the planktic/benthic (P/B) ratio and a rise in the agglutinated percentage. The results of those observations are used for revealing foraminiferal dissolution in these two zones (Racemiguembelina fructicosa CF4a and Pseudoguembelina palpebra CF2). During these two zones, there were excessive relative abundances of agglutinated foraminifera, indicating that these two intervals witnessed severe carbonate dissolution. The high total organic carbon (TOC) and low pH due to the presence of a lot of organic matter in the black shale’s of the Dakhla Formation of the upper Maastrichtian age is the explanation for the observed dissolution that has nothing to do with oceanographic or volcanic processes. The presence of pyrite within the black shale interval suggests low oxygen conditions and the potential for meteoric water to react with the pyrite and form sulfuric acid. This acid could dissolve any carbonate material well after the original deposition.

Editorial for the Special Issue “Bio-Geochemistry of Heavy Metals/Metalloids”

This Special Issue “Bio-Geochemistry of Heavy Metals/Metalloids” contains a series of papers that cover a range of topics highlighting the role of microorganisms in ore-forming biochemical processes and potential environmental risk (the first to fourth papers), in the assessment of potentially toxic element contamination using plants and living benthic Foraminifera (the fifth and sixth papers), and in the phytoremediation of contaminated land (the seventh paper) [...]