Benthic Foraminifera Assemblages Research Articles

Bottom water redox dynamics during the Early Cretaceous Weissert Event in ODP Hole 692B (Weddell Sea, Antarctica) reconstructed from the benthic foraminiferal assemblages

Benthic foraminifera at Ocean Drilling Program (ODP) Hole 692B were studied to understand variations in oxygen and organic-matter fluxes in bottom waters during the Early Cretaceous. The upper Berriasian to lower Barremian black shales, characterized by high concentrations of total organic carbon (TOC) ranging between 1.3 and 18%, were deposited in an outer neritic-upper bathyal environment (~200–500 m) according to benthic foraminifera assemblages. A new high-resolution record of benthic foraminiferal assemblages of high-latitude, dominated by infaunal taxa ( Citharina , Eoguttulina , Laevidentalina , Lagena , Lenticulina , Marginulina , N odosaria, Planularia , Saracenaria , and Vaginulinopsis ), is described in depleted‑oxygen and high organic‑carbon flux conditions. Extremely dysoxic conditions are recorded at the onset of the carbon isotope excursion (CIE) marking the Weissert Event (late Valanginian), followed by a period of anoxic conditions in bottom waters. A repopulation event of benthic foraminifera, linked to an increase in oxygen concentrations, coincided with the global cooling episode that characterized the late part of the Weissert Event. Subsequently, there were short periods in the late Valanginian and the late early Hauterivian when the bottom waters experienced increased oxygen concentrations. Possibly, bottom currents related to the influx of Southern Ocean waters favored short-term pulses of ventilation under constant increased organic‑carbon flux during the late Valanginian and late Hauterivian. • New Lower Cretaceous micropaleontological data from the southern high latitudes • Benthic foraminifera indicate an outer neritic-upper bathyal setting. • Alternated anoxic and dysoxic conditions during the Weissert Event in bottom-waters • Benthic foraminiferal repopulation through the Weissert Event • ODP 692B was influenced by the interplay of short-term pulses of ventilation.

New Records ofCaudriellaHaman and Huddleston from the Middle and Late Eocene of Neo-Tethys: Taxonomic and Palaeobiogeographic Implications

ABSTRACTThe middle to upper Eocene mixed carbonate-clastic and siliciclastic deposits of the Şevketiye and Keşan formations in northwest Turkey yielded unique assemblages of larger benthic foraminifera, some displaying a typical orbitoidiform test, not comparable to any known taxa in the Palaeogene of the Neo-Tethys. These specimens with a flat, discoidal test, occasionally with an indistinct central depression, possess a central layer of equatorial chambers/chamberlets displaying a cyclical (orbitoidal) growth pattern and thick lateral layers with numerous chamberlets. The megalospheric embryonic apparatus possesses three small chambers (a triconch, the chambers of which are separated by notably thin walls), followed by a large auxiliary chamberlet. These specimens closely correspond to the genus Caudriella Haman and Huddleston and its type-species Margaritella ospinae (Caudri) that has only previously been reported with confidence from the Caribbean region, notably the type locality within the middle Eocene Punta Mosquito Formation at Margarita Island off Venezuela. Caudriella at its type locality also possesses a trilocular embryonic apparatus, which was incorrectly interpreted as arranged in a rectilinear or slightly curved row. The diagnosis of Caudriella is emended and considering the similarities in their equatorial sections with closely associated Linderina Schlumberger, a comparison of their embryonic-nepionic stages is given from the same deposits in NW Turkey and with those from the middle Eocene of the Sulaiman Range (Pakistan) and Kutch (India). A new record of primitive Caudriella is presented from Jamaica. The palaeobiogeographic distribution of Caudriella is reconsidered, being recorded from both the American/Caribbean and the Western Neo-Tethys bioprovinces. Limited data suggest eastward directed dispersal of the genus, even though this would be counter to most of the prevailing surface currents during the Eocene.

Shallow Marine Cenomanian-Turonian Benthic Foraminifera and Kerogen Type from Mangoule, Logbadjeck Formation, Douala/Kribi-Campo Basin, Cameroon, West Africa

An integrated benthic foraminiferal and organic matter analysis of samples obtained from sedimentary sections exposed in the Mangoule-Bonepoupa area, revealed a very shallow marine paleo-depositional environment for the sediments studied, with considerable influx of continental organic matter that were accumulated during the Cenomanian-Turonian age. With reference to the lithostratigraphic profile of the Douala/Kribi-Campo Basin, the age obtained reveals that the sedimentary sections studied belong particularly to the lower section of the Logbadjeck/Mungo River Formation, based on the following benthic foraminifera assemblage: Ammobaculites jessensis, Ammobaculites benuensis, Ammobaculites coprolithiformis, Ammotium cf nkalagum, Ammotium nwalum, Haplophragmoides cf beuchensis, Trochamina taylorana. A particularly very poor palynomorph assemblage was recovered and included no age diagnostic species: Acrostichum aureum, Lycopodiumsporites sp., Fungal spore, Lavigatosporites discordatus, Longapertites sp., Verrucosisporites sp. An organic petrographic analysis performed on these samples revealed Kerogen Type-II and Type-III. The entire data sets obtained from this area is remarkably poor and we suspect poor preservation as the cause viewing the extent of weathering. The paleo-depositional environment of these sediments was suggested both from the foraminifera and palynomorphs present and confirmed from the organic matter types and macrofossil contents. The studied sections are composed generally of dark to dark-gray shale beds. As one of the petroleum producing basins within the Gulf of Guinea in which exploration/exploitation activities are on-going, the current research is aim at providing more data useful in the continuous search for more potential source rocks in this basin.

Spatiotemporal assessment of the environmental quality of bottom waters through the study of benthic foraminifera in a semi-enclosed gulf

The evolution of the bottom water in Amvrakikos Gulf in Ionian Sea at western Greece for a 50-year timespan was assessed by benthic foraminifera assemblages. The degradation of the bottom water of Amvrakikos has been a catalyst for the surface water degradation. The east basin has shown permanent low environmental quality in bottom waters since 1980, while the west basin has been under seasonal hypoxic regime since 2000. The most adverse environmental conditions occurred in 1990–2000 and 2005–2010 coinciding with the recorded fish mortality events. The major cause of the environmental quality improvement of the bottom water is the intrusion of seawater. In western areas of the gulf, where the influence of the seawater is high, the decreased temperature improves the environmental conditions, while in the areas influenced by river discharges (east and northern), the environmental conditions are depended on multiple causes like organic matter input and surface salinity.

Dynamics of large benthic foraminiferal assemblages: A tool to foreshadow reef degradation?

Ecological regime shifts in the marine realm have been recorded from a variety of systems and locations around the world. Coral reefs have been especially affected, with their benthic habitat changing from a dominance of stony corals to a dominance of other organisms such as fleshy algae. To detect changes in the benthic habitat of coral reefs, simple tools applicable on a global scale are necessary for future monitoring programs. Hence, the aim of this research is to explore the hypothesis that shifts in assemblages of large benthic foraminifera (LBF) can detect early signs of degradation in the reef benthic habitat. To do so, data on living assemblages of LBF collected between 1997 and 2018 at 12 islands in the Spermonde Archipelago (South Sulawesi, Indonesia) were analyzed. Foraminiferal specimens were morphologically identified to the species level and statistical analyses performed to assess changes in their assemblage composition. A clear temporal shift was observed. Typical foraminiferal assemblages in a coral-dominated (e.g., Amphistegina lobifera, Calcarina spengleri, Heterostegina depressa) and fleshy algae-dominated (e.g., Neorotalia gaimardi, C. mayori) reef habitats were identified and significantly linked to the substrate type. Other species (e.g., Elphidium spp., Peneroplis planatus and Sphaerogypsina globulus) seem to reflect a spatial and temporal gradient of anthropogenic pollution from local inhabited islands and ongoing urban development on the mainland. Hence communities of LBF consistently follow gradual shifts in environmental conditions. Additionally to foraminiferal assemblages being an indicator for actual reef condition, closely monitoring LBF may provide early information on reef degradation, in time to take action against identified stressors (e.g., eutrophication or intensive fishing) at local and regional scales. The circumtropical distribution of LBF is such that they can be included worldwide in reef monitoring programs, conditional to calibration to the regional species pool.

Could Norwegian fjords serve as an analogue for the future of the Svalbard fjords? State and fate of high latitude fjords in the face of progressive \u201catlantification\u201d

Benthic foraminifera are one of the most widely and abundantly distributed organisms in the fjords of Svalbard and Norway. Due to their short life span and quick reactivity to environmental changes they can be used as indicators of the “atlantification” process. Here, we compare the benthic foraminifera assemblages along the latitudinal gradient, from the fjords of northern Svalbard to southern Norway to assess whether the “atlantification” process may homogenise the foraminiferal assemblages in terms of their abundance and species composition. Furthermore, the previously published data on benthic foraminiferal faunas was updated to identify changes in distribution that have occurred over the last few decades. For this purpose, fjord mouths in western and northern Svalbard (Isfjorden, Wijdefjorden and Rijpfjorden) and northern and southern Norway (Balsfjorden, Raunefjorden and Hjeltefjorden) were resampled. The analysis revealed similarities between the Svalbard and Norwegian foraminiferal assemblages of up to 30%; however, there were essential differences in terms of abundance and biodiversity. These results suggest that Svalbard fjords will remain distinct in the future, even under conditions of further warming or “atlantification”. Svalbard fjords may be dominated by Atlantic Water- preferring species, whereas, in Norwegian fjords, pressure from human activity will probably be the main driver of environmental changes, leading to changes in the foraminiferal assemblages with the increasing dominance of opportunistic, hypoxia-tolerant species.

Miocene paleoceanographic evolution of the Mediterranean area and carbonate production changes: A review

Miocene is a key interval in the global climate evolution as well as in the geodynamic evolution of the Mediterranean basin. Therefore, global and regional factors controlled Miocene Mediterranean oceanography, which, in turn, affected carbonate production. In this work, we review the Miocene paleocenographic evolution of the Mediterranean starting from its Sr and Nd isotope records. Secondly, we discuss Mediterranean shallow-water carbonate production changes to identify the role of oceanographic conditions in controlling carbonate systems' evolution. During Aquitanian, Sr and Nd isotope records attest an open Mediterranean, mainly fed by the Indian Ocean. From the late Burdigalian, the intermittent connection with the Indian Ocean changed the overall circulation in the basin, leading to higher residence time of waters and smaller water exchanges with the adjacent oceans. In this newly established paleoceanographic framework, regional factors such as volcanism, significantly affected Mediterranean seawater chemistry. Local tectonics led to the development of small sub-basins in the Eastern Mediterranean, characterized by restricted water exchanges from the Tortonian in the easternmost part, to the early Messinian, as attested by the deviation of the Sr isotope record of the proto-Adriatic basin. Larger Benthic Foraminifera (LBF) assemblages dominated carbonate production in the Aquitanian, while they were the most affected by the Indo-Pacific closure, showing a demise after the Burdigalian. With the LBF demise, red algae and bryozoans dominated carbonate ramps from the middle Miocene to the Tortonian. Bryozoans in particular spread during the Monterey Event, favoured by global and regional factors. During early to middle Miocene, corals formed mounds in the oligophotic zone or coral carpets controlled by local conditions. Conversely, in the late Tortonian-early Messinian, they developed as huge reef complexes in the Western and Central Mediterranean, with the exception of small restricted sub-basins, such as the proto-Adriatic basin, where red algae and small benthic foraminifera persisted.

Untangling the effect of organic matter and dissolved oxygen on living benthic foraminifera in the southeastern Arabian Sea

We studied the relationship between organic carbon in sediments (%Corg), bottom water dissolved oxygen and living benthic foraminifera in a marginal marine upwelling setting from the southeastern Arabian Sea to develop proxy indicator for marine productivity as well as oxygen deficient zones. The surface sediments from 43 stations covering a depth range of 25 to 2980 m were used. The relationship between living benthic foraminifera and ambient environmental parameters (seawater temperature, salinity, dissolved oxygen, organic carbon and Corg/TN and depth) was assessed by multivariate analysis. A majority of the living benthic foraminifera were significantly affected by several ambient parameters. We report that the living benthic foraminiferal assemblage comprising of Epistominella umbonifera, Uvigerina auberiana, Reophax longicollis and Osangularia bengalensis is significantly affected only by %Corg in the sediment. Additionally, we also found that the assemblage including Bolivina obscuranta, Bulimina arabiensis, Bulimina pseudoaffinis and Cancris penangensis is significantly affected only by the bottom water dissolved oxygen. The living benthic foraminifera assemblages can be used to reconstruct marine productivity and dissolved oxygen concentration in the past.

Benthic foraminifera from the Albian shallow-marine limestones in the Geyik Dağı area (Central Taurides), southern Turkey

AbstractCretaceous carbonates in the Geyik Dağı area (Central Taurides, southern Turkey) are represented by two successions with different paleoenvironmental settings: open shelf to slope succession of Cenomanian to Danian age and inner platform succession of Albian to Maastrichtian age, which is interrupted by a post-Cenomanian disconformity. Outcropped lowermost part of the platform-type one is composed of rudistid limestones corresponding to the Urgonian-type carbonates and belongs to the Geyik Dağı Unit (=Anamas-Akseki Carbonate Platform). It contains a rich assemblage of larger benthic foraminifera including orbitolinid, chrysalidinid, cuneolinid, nezzazatid, and miliolid taxa, which has been illustrated and documented here for the first time from the upper Albian of the Tauride Carbonate Platform. The occurrence of such a diversified foraminiferal fauna indicates a prominent high diversity that took place in the Tauride Carbonate Platform during the late Albian time, which corresponds to a major emersion period in some parts of the platform.

Living (stained) calcareous benthic foraminiferal assemblages ([formula omitted]) in a coastal upwelling zone of the Humboldt Current System, Northern Chile ([formula omitted]S)

In coastal upwelling ecosystems, understanding of environmental factors regulating the structure of benthic foraminiferal communities is fundamental to enhance our knowledge of their ecology and to validate their use in palaeoceanographic studies. In this study, we assess the influence of organic matter (quantity/quality) and subsurface oxygenation on living (stained) calcareous benthic foraminifera inhabiting a coastal upwelling ecosystem influenced by Oxygen Minimum Zone (OMZ) off Inglesa Bay, Northern Chile. Benthic foraminifera and their environment (i.e. biochemical/elemental sediment composition and subsurface water column oxygenation) were sampled along a transect perpendicular to the coastline consisting of three stations (30, 70 and 120 m) and covering two seasons (winter and summer). The geochemical composition of surface sediments and subsurface oxygenation reveal a typical pattern of marine ecosystems associated with coastal upwelling centers influenced by OMZ. Forty-seven species of living calcareous benthic foraminifera were identified, in which Bolivinella seminuda, Buliminella elegantissima, Bulimina marginata, and Nonionella miocenica were found as the most abundant species. Total abundance increases remarkably with depth while taxonomic richness and evenness decrease. Multivariate analyses show three benthic foraminiferal associations strongly linked to nutritive organic matter and subsurface oxygenation, regardless of the sampling period. Assemblages “A” (22 species, 4 dominant) and “C” (5 species, 1 dominant) are associated with the shallow (30 m) and deep (120 m) station, and present contrasting subsurface oxygenation and organic matter content. Assemblage “B” (19 species, 3 dominant) is associated with the intermediate station (70 m) characterized by mixed subsurface oxygenation and organic matter content. Our results suggest that local environment conditions (i.e. OMZ intensity, organic matter quality/quantity) govern the structure and composition of the living calcareous benthic foraminiferal assemblages of Inglesa Bay. Such assemblages have similarities and differences with other benthic foraminifera assemblages found in other coastal upwelling ecosystems impinged by an OMZ.

Lowermost Cretaceous biostratigraphy and paleoenvironmental features of the central-western Getic Carbonate Platform (Pui-Bănița zone, Southern Carpathians, Romania): A holistic approach

We carried out combined micropaleontological, microfacies and multivariate statistical analyses of benthic foraminiferal assemblages on a previously undocumented lowermost Cretaceous carbonate succession from the western part of the Getic Carbonate Platform (Pui-Bănița zone, Southern Carpathians). The microfacies analysis and interpretations suggest that these limestones were developed under peritidal settings within different zones of a shallow-water inner platform paleoenvironment (bioclastic grainy bars, subtidal–intertidal flats and intertidal–supratidal ponds), where benthic foraminifera, microbial microstructures and calcareous algae were the main carbonate producers. The well-preserved micropaleontological content (mostly benthic foraminiferal assemblages) is important for lowermost Cretaceous Neotethyan biostratigraphy and allows the recognition of the Valanginian stage within this part of the Getic Carbonate Platform. The multivariate data processing (diversity indices, cluster analyses and principal components analyses) performed on the benthic foraminifera assemblages provide valuable information about their compositional patterns, diversity trends and spatial distribution with respect to the main facies zones. The results obtained through these analyses are extremely useful for the recognition of common/different paleoecological features and for a more precise interpretation of depositional paleoenvironments.

Biotic response of benthic foraminifera to OMZ variations in the northwestern Pacific since the last deglaciation

Recent declines in oxygen concentrations in the global oceans have been particularly acute in oxygen minimum zones (OMZ) at intermediate depths. Fossil benthic foraminifera have the potential to provide useful information on the long-term biotic responses of marine organisms to past variations in the OMZ. During the last deglaciation, the OMZ at 1 km water depth in the northwestern Pacific Ocean intensified. However, temporal variations in benthic foraminifera in the upper layer of the OMZ since the last deglaciation are poorly understood. Thus, we studied temporal variations in benthic foraminifera assemblages in a sediment core taken from a water depth of 777 m off of Hokkaido, North Japan, to determine their biotic responses to environmental changes in the upper layer of the OMZ from the last deglaciation to the late Holocene. The results suggested that dysoxic species such as Bolivina seminuda and Buliminella tenuata increased rapidly during the Bolling/Allerod warming event, which was associated with severe oxygen depletion and expansion of the OMZ. Similar dysoxic assemblages were recorded at 1 km water depth in this region. On the other hand, the dominance of the oxic species Nonionellina labradorica during the Younger Dryas cold period may indicate that oxygenation events were induced by intensification of intermediate water ventilation. Suboxic assemblages composed of Uvigerina akitaensis, Bolivina spissa, and Elphidium batialis appeared in the late Holocene. The increase in this late Holocene assemblage, which is similar to the modern assemblage in this region, may coincide with gradual cooling around the Japanese Islands.

A preliminary investigation of Eocene larger benthic foraminifera assemblages from Alpine and molasse-type deposits of the Hellenic peninsula (Greece)

Larger Benthic Foraminifera (LBF) from five localities in Greece were studied in order to define the morphological features of various nummulitid forms and to describe the foraminiferal assemblages in different geotectonic environments. The selected sites belong to molasse-type formations in Kirki/Thrace Basin and Vasiliki Trikala/Mesohellenic Trough, and carbonate deposits in Alpine Pindos, Ionian and Tripolis geotectonic units.Taxonomic studies combined with biometric data, when possible, enabled us to identify different morphotypes. In the molasse-type deposits of Thrace Basin (Kirki Thrace), N. perforatus was found along with N. maximus and Assilina exponens suggesting correlation with biozone SBZ 16/17, while in the Mesohellenic Trough deposits (Vasiliki Trikala) the association included N. perforatus group, Operculina gomezi group and Silvestriella tetraedra, indicating a Bartonian age, SBZ 17-18A. In outcrops found within Pindos unit (Perivoli Grevena) three different assemblages have been observed in the microbreccious olistholiths, suggesting three distinguished deposits forming quasi-continuous succession spanning from early to middle and up to late Eocene. The Ionian unit (Manoliasa Ioannina) presented a mixed redeposited fauna including late Eocene, early Paleogene and planktonic foraminifera clasts. Finally, the Tripolis unit (Dervenakia and Tripolis) association was interpreted as Bartonian in age, defined by the presence of Operculina gomezi group and N. perforatus group.

Paleoceanographic evolution of the Gulf of Tehuantepec (Mexican Pacific) during the last ~6 millennia

Oceanographic dynamics in the Gulf of Tehuantepec (GT) are the direct consequence of climate variability, mainly influenced by the strong wind regime locally called “Tehuanos” and the interactions between the Intertropical Convergence Zone (ITCZ) and El Niño Southern Oscillation (ENSO). The area is characterized by intense upwelling driven by the Tehuanos within one of the largest Oxygen Minimum Zones (OMZ) in the world. Upwelling carries nutrient-rich subsurface waters to the surface and provides marine resources to the coasts conforming one of the main economic sectors in the region. In this study, sediment core MD02-2521 is used to perform the first high-resolution paleoceanographic reconstruction of the last 6 millennia in the GT. The main focus is put on the analysis of the benthic foraminifera (BF) assemblages inhabiting within the OMZ, which appear to respond to bottom oxygenation and climate variations of the last ~6000 years. The microfossil assemblages throughout the sediment core revealed, first, intervals where the lack of foraminifera provide evidence of episodes of strong deoxygenation that triggered the dissolution of calcareous foraminiferal tests, second, a long-term decline of bottom-water oxygenation in the last ~2500 years likely responding to the southward migration of the ITCZ. Last, variations in response to the transitions between cold and warm periods occurred during the last 2–2.5 millennia and cyclicities of 1470 years resembling Bond Cycles suggest a climatic connection between the Pacific and Atlantic Oceans during the late-Holocene.

Reservoir quality of the Surmeh (Arab-D) reservoir in the context of sequence stratigraphy in Salman Field, Persian Gulf

The Upper Jurassic Surmeh reservoir in the northern Persian Gulf is a stratigraphic equivalent of Arab-D reservoir that is one of the best Jurassic reservoir rocks of the Arabian Peninsula. In this study, in the first step the palaeontology, sedimentary environment, sequence stratigraphy and reservoir quality of the Surmeh reservoir was investigated in a core-bearing well in Salman oil field. The palaeontological studies reveal a moderately diverse assemblage of benthic foraminifera. Dominated foraminifera include the agglutinated forms and miliolids and there are also fragments of alga, stromatoporoids, corals, bivalves, gastropods and echinoderms. These recorded fauna and flora resulted in distinction of three zones that characterize the age of undifferentiated Kimmeridgian-Tithonian. Based on petrographic observations, along with palaeontological materials, eight microfacies were identified that represent four sub-environments of a carbonate inner ramp including supratidal, intertidal, lagoon and shoal. These studies combined with well log responses resulted in identification of a 3rd order sequence and parts of an incomplete one that is composed of an incomplete HST. These 3rd order sequences comprise four 4th order subordinate sequences.In addition by integration of petrographic analyses, sub-environments energy regimes and petrophysical data, five reservoir zones were identified. Also, based on core porosity and permeability 6 Hydraulic Flow Unit (HFU) with poor to excellent reservoir quality in ascending trend were identified. The reservoir zone I, which belongs to the sabkha and littoral facies, represents the worst reservoir quality (includes HFU1 to HFU3), while the reservoir zone III with best reservoir quality (includes HFU4 and HFU5) comprises the back shoal grain-supported facies. The introduced sequences and reservoir zones in the studied well were propagated to three other wells throughout the Salman Field via using log responses. Also they were correlated with those introduced for Arab-D reservoir in the southern parts of the Persian Gulf providing a correlation framework. This pattern can be used in the next exploration wells which are going to be drilled especially in the northern parts of the Persian Gulf.

Benthic foraminifera as bio-indicator of Mangrove ecosystem quality: A case study from Abu Ghoson area, Red Sea Coast, Egypt

The assemblages of benthic foraminifera were studied in surface sediment samples collected along two transects from the mangrove swamp and the intertidal flat zone in Abu Ghoson area, the Red Sea coast of Egypt, to validate and support their use as bio-indicators of ecosystem quality. Using Q-mode and R-mode cluster analyses, three biotopes following the bathymetric and environmental gradients have been documented. The seaward intertidal flat stations were dominated by larger symbiont-bearing foraminifera (Peneroplis planatus, Peneroplis pertusus, Sorites orbiculus, Coscinospira spp., and Amphisorous spp.). This biotope reflects the oligotrophic environment. Assemblage of smaller miliolids and rotaliids is diversified and characterized the swamp stations and the closest intertidal stations. The assemblage from the most landward semi-closed swamp station was distinguished by stress-tolerant taxa, especially Ammonia tepida, found in high percentages, though relatively low diversity.

Systematic and biostratigraphic evaluation of the Late Cretaceous benthic foraminifera assemblages of southeastern Batman

Systematic and biostratigraphic evaluation of the Late Cretaceous benthic foraminifera assemblages of southeastern Batman

Foraminifera Biostratigraphy, Palynofacies and Paleoenvironment of deposition of the Albian to Santonian sediments in the Southern Benue Trough, Nigeria

The Albian-Santonian sedimentary sequence in the Ndeaboh-Nenwe area of Enugu, Southern Benue Trough, were analysed for foraminifera and integrated with ostracod and palynofacies analyses to comprehensively appraise the age and depositional environment of the sediments. This is paramount since the studied formations have intermittent series of non-marine sedimentary influences throughout the basin. The results of foraminifera evaluation indicate that the Abakaliki Formation is barren of foraminifera species, whereas the Eze-Aku and Awgu formations have preponderance of planktonic foraminifera assemblages over benthic forms. The Eze-Aku Formation records an abundance of species of Hedbergella and a peak for Heterohelix. The co-occurrence of Whiteinella archeocretacea, Hedbergella planispira, Heterohelix delrieonsis and the ostracod species Ovocytherida symmetrica, suggests a Late Cenomanian to Early Turonian age. Rare species of short-ranging and keeled planktonic taxa are present in Awgu Formation, which has a preponderance of Heterohelix reussi, Heteroheix globulosa, Heterhelix pulchra, Whiteinella baltica, and the ostracods Brachycythere ekpo and Cythereis sp. The Awgu Formation is Middle Turonian to Santonian. The percentage of amorphous organic matter and lithologic characteristics suggest a marine environment for the Abakaliki Formation, although the water depth cannot be ascertained. In the Eze-Aku Formation, the prevalence of Hedbergella and its co-occurrence with Whiteinella and associated palynofacies data (amorphous organic matter, black debris, few structured terrestrial phytoclasts) and dinoflagellate cysts suggest a fairly deep (200–300 m) marine environment with occasional terrestrial input. The low diversity of agglutinated benthic foraminifera assemblage in the Awgu Formation indicates deposition at a minimum paleo-water depth. The paucity of benthic foraminifera, rare occurrence of keeled planktonic species, and the dominance of Hedbergella and Heterohelix; low oxygen tolerant species, in the studied interval are attributed to anaerobic bottom conditions possibly caused by poor bottom water circulation and high organic productivity in the oceans and seas during the Cenomanian-Santonian.

Development of a benthic foraminifera based marine biotic index (Foram-AMBI) for the Gulf of Mexico: A decision support tool

The Gulf of Mexico (GoM) is an economically important region (e.g. oil and gas, fisheries) and with the expansion of oil drilling, harmful algal bloom events, oil blowouts, dead zones, anthropogenic eutrophication and contaminant loading, it is important that the ecological quality statuses (EcoQS) of different localities in the Gulf are closely monitored. The EcoQS, as implemented by the European Water Framework Directive, is an effective tool for monitoring ecological health and developing reference conditions. One such index used to define EcoQS is the AZTI Marine Biotic Index (AMBI), which pairs species abundance with environmental stressors. Benthic foraminifera are ideal specimens to populate the index due to their varying environmental sensitivities among species, preservation potential, and high diversity and abundance in nearly every marine environment. To calculate the benthic foraminiferal AMBI (Foram-AMBI), species are assigned to one of five groups ranging from sensitive (I) to first-order opportunists (V) based on their correlation to total organic matter and sediment grain size. This study constructs a Foram-AMBI from benthic foraminifera assemblages collected at 59 sites throughout the GoM. This approach provides reference EcoQS for the GoM and will satisfy the need for widespread geospatial coverage in the case of future natural or anthropogenic disturbances. This study provides a master assignment list of 155 species and identification plates of 44 of those species from a depth range of 42 m-2975 m. The development of a GoM Foram-AMBI encourages collaborative partnerships between academic scientists and living resource managers throughout the GoM to operationalize, refine and implement the Foram-AMBI as a decision support tool.

Palaeoceanographic and palaeoclimatic changes during the last 37,000 years detected in the SE Bay of Biscay based on benthic foraminifera

Benthic foraminifera assemblages from a sedimentary core (PP10-12; 701 mwd) from the SE Bay of Biscay allow us to trace palaeoceanographic and palaeoclimatic changes occurred in this region during mid MIS 3 (Marine Isotope Stage 3) and MIS 1 interval (37–2.4 ka BP). Results are based on 176 benthic foraminifera species considering their ecology, the difference between autochthonous/allochthonous, preservation and oxygen rates, thus evidencing climatic and oceanographic events. MIS 3 is characterised by waters with a dominance of Cassidulina laevigata and Uvigerina peregrina. By the end of this interval, waters became colder and less oxygenated indicated by the occurrence of Melonis affinis. These conditions persisted at the beginning of MIS 2. The Heinrich Event 1 (H1) is well registered in this core with three intervals (H1a, H1s.s., H1b) where Hyalinea balthica dominates. During H1s.s. the coldest waters are registered, and the environment was unstable. These conditions continued during H1b when the occurrence of Globobulimina affinis evidences some intervals with anoxia. During Bølling-Allerød (B/A) waters were warmer and low-ventilated indicated by Bulimina gibba. Cassidulina laevigata dominates the Younger Dryas (YD) and the beginning of Lower Holocene, evidencing the occurrence of cool waters with low-oxygen and high organic matter content. The Lower to Middle Holocene transition is registered as a cold interval: Holocene Cooling Event (HCE-5). From the Middle Holocene onward water temperature were milder based on the dominance of Uvigerina peregrina.