Foraminiferal Assemblages Research Articles

Understanding the Distributions of Benthic Foraminifera in the Adriatic Sea with Gradient Forest and Structural Equation Models

In the last three decades, benthic foraminiferal ecology has been intensively investigated to improve the potential application of these marine organisms as proxies of the effects of climate change and other global change phenomena. It is still challenging to define the most important factors affecting foraminiferal communities and derived faunistic parameters. In this study, we examined the abiotic-biotic relationships of foraminiferal communities in the central-southern area of the Adriatic Sea using modern machine learning techniques. We combined gradient forest (Gf) and structural equation modeling (SEM) to test hypotheses about determinants of benthic foraminiferal assemblages. These approaches helped determine the relative effect of sizes of different environmental variables responsible for shaping living foraminiferal distributions. Four major faunal turnovers (at 13–28 m, 29–58 m, 59–215 m, and >215 m) were identified along a large bathymetric gradient (13–703 m water depth) that reflected the classical bathymetric distribution of benthic communities. Sand and organic matter (OM) contents were identified as the most relevant factors influencing the distribution of foraminifera either along the entire depth gradient or at selected bathymetric ranges. The SEM supported causal hypotheses that focused the factors that shaped assemblages at each bathymetric range, and the most notable causal relationships were direct effects of depth and indirect effects of the Gf-identified environmental parameters (i.e., sand, pollution load Index–PLI, organic matter–OM and total nitrogen–N) on foraminifera infauna and diversity. These results are relevant to understanding the basic ecology and conservation of foraminiferal communities.

Nutrients and hydrography explain the composition of recent Mediterranean planktonic foraminiferal assemblages

The composition of planktonic foraminiferal assemblages in surface sediments of the Mediterranean Sea shows a pronounced zonal gradient. This gradient is different from what is observed in the open ocean, indicating that the assemblage composition may respond to environmental variables other than the otherwise dominant surface water temperature. Here we make use of a dataset of census counts of 18 taxonomic categories in 124 surface-sediment samples extracted from the ForCenS database to understand the main environmental factors affecting the composition of recent Mediterranean planktonic foraminiferal assemblages. The tested explanatory variables include temperature, salinity, chlorophyll, nitrate and phosphate concentrations in the surface waters, temperature, nitrate and phosphate concentrations at depth and thermal, salinity and density vertical gradients. The composition of the assemblages is aligned along two environmental gradients and redundancy analysis reveals that the tested variables explain a large portion (>70%) of the variance in the compositional data. The first environmental gradient reflects the nutrient content in the deep waters, affecting nutrient availability in the productive zone, while the second gradient is driven by higher (northern area) and lower (southern area) upward nutrient advection due to differences in density stratification, conditioned by the regional hydrography. Although sea surface temperature is the most reconstructed environmental variable from fossil assemblages of planktonic foraminifera, it seems to play a secondary role in the Mediterranean Sea. This, has implications for reconstructions of past oceanographic conditions in this region, opening up the possibility to reconstruct productivity instead, or next to, temperature.

Middle Eocene (Lutetian-Bartonian) larger benthic foraminifera assemblages from Batman and Siirt (Southern Neotethys, SE Turkey): a new assessment

The benthic foraminifera assemblage has been described in the limestones outcropped in Kurtalan and Eruh district of Hoya formation which is one of autochthonous units of Arabian Platform (SE Turkey). From the two measured sections, one of them has rare fossil content due to dolomitization (DH-Dodan section),while the other is fairly remarkable in terms of fossil content (EH-Eruh section). The foraminiferal assemblages are represented by Asterigerina rotula (Kaufmann), Operculina ex. gr. gomezi Colom and Bauza, Victoriella conoidea Rutten, Amphistegina sp., Elphidium sp., Peneroplis sp., Carpenteria sp., Stomatorbina sp., miliolid and rotaliid forms and echinoderms, coral fragments in the Dodan section. The foraminiferal assemblages are represented by Nummulites biedai Schaub, Nummulites maximus d’Archiac, Nummulites perforatus de Montfort, Nummulites postfossulatus Sirel and Deveciler, Nummulites praeaturicus Schaub, Assilina exponens (Sowerby), Sphaerogypsina globulus (Reuss), Asterigerina rotula (Kaufmann), Lockhartia cf. hunti Ovey, Neoratlia sp., Operculina sp., Discocyclina sp., Asterocyclina sp., Lockhartia sp., Lenticulina sp., miliolid-rotaliid forms and echinoderms in the Eruh section. The fossil assemblage described shows that the limestones are of Lutetian-Bartonian and this assemblage indicates a very shallow marine deposition environment. This study provides biostratigraphic and stratigraphic data that help to reassess the Eocene geological evolution of the region. Paleobiogeographically, larger benthic foraminiferal assemblages recorded on carbonate platforms in southeastern Turkey show an affinity to Arabian and Middle Eastern platforms.

Tectonic setting, provenance, depositional, and paleo-climatic conditions of the late quaternary subcrop sediments of the southeastern coastal region of the Bengal basin

This is a systematic attempt to depict the genetic evolution of the Late Quaternary sediments of the southeastern (SE) coastal region of the Bengal basin regarding paleotectonic settings, sedimentation, provenance, paleo-climatic conditions, weathering condition and age. The study has considered multiple attributes such as, lithology/lithofacies, sedimentary features/records, major oxides, clay minerals, foraminifera, and radiocarbon dating. The lithological characters along with associated clay minerals confirmed that a Pleistocene paleosol horizon (over-bank deposits) of warm-humid nature is commonly encountered immediately on top of the sub-crop bed-rock in the area overlain by Holocene fluvio-marine sediments of the same nature. The lithofacies, foraminiferal assemblages, and sedimentary structures of the analyzed samples suggest that the Holocene sediments have been presumably deposited in a fluvio-marine condition after the Last Glacial Maximum (LGM) due to the transgression of the sea. Geochemically, the sediments are classified as Fe-rich shale, shale, and wake and primarily intermediate to felsic orogen provenance. These are possibly derived from intense weathered sources from the upheaval of Himalayan ranges of both active continental margin and Island Arc paleotectonic setting. The plot of the Index of Compositional Variability versus the Chemical Index of Alteration indicates that the sediments seemingly experienced intense weathering associated with warm and humid climatic conditions. The sedimentation rates of the area vary from place to place and layer to layer due to the complex delta-building process. The reconstructed Relative Sea Level Curve reveals that presumably, the sea level has reached its current position after the LGM. The deduction possibly will facilitate the (1) reconstruction of Late Quaternary coastal evolution after LGM, (2) support for future urbanization, land use plans, etc., and (3) also be helpful for international researchers to understand the possible sources of sediment input in the area from the complex interplay of the Indian-, Eurasian- and Myanmar-plates.

New Triassic finding in Andız Peninsula (İzmir, Western Turkey) and comparison of pre-Neogene sequences of Andız and Karaburun Peninsulas: Stratigraphic and tectonic implications

This study aims to review the geology of the Andız Peninsula and compare the pre-Neogene Andız succession with the middle part of the Karaburun Peninsula to discuss the nature of the Paleozoic-Mesozoic boundary in the Karaburun Peninsula. The pre-Neogene units of the Andız Peninsula are represented by the Paleozoic Dikendağı, Triassic Gu?vercinlik, and Jurassic Nohutalan Formations. In this study, the Triassic carbonate rocks in the Andız Peninsula are paleontologically defined for the first time. The Megalodont-bearing Gu?vercinlik Formation contains a late Norian-Rhaetian characteristic foraminiferal assemblage consisting of Aulotortus gr. sinuosus, A. tenuis, A. friedli, A. impressus, and Triasina hantkeni. The Thaumatoporella-bearing Nohutalan Formation conformably overlies the Gu?vercinlik Formation and yields a typical Liassic fossil assemblage of Orbitopsella praecursor, Siphovalvulina gibralterensis, S. colomi, Meandrovoluta asiagoensis, and Palaeodasycladus mediterraneus. In the Andız Peninsula, the Mesozoic Gu?vercinlik and Nohutalan Formations tectonically overlie the Paleozoic Dikendağı Formation along a displacement contact. In the middle Karaburun Peninsula, the Triassic Gerence Formation lies directly on the Dikendağı Formation along a displacement contact. Lateral continuation of this displacement contact is discovered between the Triassic Gerence and Camiboğazı Formations at the top and Paleozoic Dikendağı Formation at the bottom. Further north, the same displacement contact extends into the Paleozoic sequence where the Carboniferous Alandere Formation tectonically overlies the Dikendağı Formation. These observations suggest that the succession in the Karaburun Peninsula ranging from Bashkirian to Cretaceous, is a tectonic slice or a package of slices over the Dikendağı Formation.

Planktonic foraminiferal biostratigraphy of the Farrokhi Formation and determination of the Campanian/Maastrichtian boundary in Central Iran

The Cretaceous Farrokhi Formation is located in the Khur area of central Iran and yielded a reasonably well-preserved rich planktonic foraminiferal assemblage. This formation consists of 154 m of fossiliferous marl and limestone. The lower and upper bounding surfaces of the Farrokhi Formation are unconformable with the underlying Haftoman Formation and the overlying Chupanan Formation. In this research, 46 planktonic foraminiferal species belonging to 19 genera were identified and resulted in recognition of the following three biozones (from base to top); the Globotruncana aegyptiaca Interval Zone (IZ), the Gansserina gansseri IZ, and the Contusotruncana contusa IZ. This biozonal framework places deposition of the Farrokhi Formation during the late Campanian to early Maastrichtian. Biostratigraphic comparison between the samples for this research and data from three other studied sections within the Farrokhi Formation indicates that the basal and upper boundaries of the formation are time-transgressive and migrate chronologically from north to southeast. Since the first occurrences of Pseudoguembelina palpebra and Rugoglobigerina pennyi mark the latest Campanian worldwide, we approximate the Campanian/Maastrichtian boundary based on the FOs of Trinitella scotti and Rugoglobigerina hexacamerata, and identify the basal Maastrichtian by the last occurrence of Laeviella bollii.

Pleistocene Paleoceanographic Conditions in the Ioffe Drift Area (South Atlantic) Based on Benthic Foraminiferal Assemblages

The Ioffe Drift located in the western South Atlantic to the north-east to the Vema Channel was discovered in the 32nd cruise of the R/V “Akademik Ioffe” in 2010. The analysis of the seismoacoustic, biostratigraphic, lithological, grain-size, geochemical and X-ray fluorescence data allowed to estimate the Pleistocene age of the upper part of the drift as well as to confirm contourite genesis of the sediments. Quantitative analyses of benthic foraminiferal assemblages are carried out in the sediment core AI-2436 (26°51.6′ S, 34°01.40′ W, 3800 m water depth) collected near the drift summit. The obtained results allowed reconstructing relative changes of the organic matter flux to the seafloor, its periodicity and bottom current intensity as well as suggesting interplay of the deep-water masses during the Pleistocene. Visual evaluation of benthic foraminiferal tests allowed distinguishing three groups of damages of presumably variable genesis. First group includes damages possibly resulted from impacts of particles transporting by bottom currents. Second group consists of damages that appeared due to movement of the tests by strong bottom currents. Third group contains deformations caused by dissolution in carbonate-aggressive bottom-water environment. Thus, specific features of the tests in combination with traditional methods may serve as a supporting technique for diagnostics of contourites. However, this method demands a development of application criteria and should be verified on reliable material.

Evidence of upwelling on the Brazilian continental shelf of Rio Grande do Norte

This study evaluates Foraminiferal assemblages and their relation with grain size, calcium carbonate content, organic matter, and mineralogy of sediment samples collected at the sediment-water interface along a transect on the northern continental shelf of Rio Grande do Norte State, Brazil, adjacent to the city of Areia Branca. The sedimentary sequence of this shelf is represented by lithostratigraphic units of a marine regressive sequence dominated by four facies: Siliciclastic sand, Silicibioclastic Sand, carbonate mud, and Biosiliciclastic sand. The carbonate content ranged from 5.83% to 85% and the organic matter content from 1.16% to 27.05%. Mineralogical characters separated the predominant siliciclastic content (37% to 92%) from the bioclastic content (8% to 63%). We have identified 14 species out of 50 species of Foraminifera, associated to particular depths and sediment types as follows: (1)deeper-water sediments in the middle shelf contain Bolivina striatula, Bulimina marginata, Triloculina trigonula, Pyrgo ringens, Textularia gramen (2)the shallowest sediments in the inner shelf contain Ammonia tepida, Buccella peruviana, Miliolinella subrotunda, and Quinqueloculina patagonica, (3)the central parts of the transect, also in the inner shelf, provide habitats for Quinqueloculina lamarckiana, Textularia earlandi, Buliminella elegantissima, Discorbis peruvianus, and Pyrgo nasuta. The distribution of Uvigerina striata and Buccella peruviana is probably related to colder water temperatures and possibly the occurrence of an upwelling phenomenon for the deepest parts of the area rather than the sedimentological features discussed here.

Priabonian (upper Eocene) larger foraminifera from the Helvetic Nappes of the Alps (Western Switzerland): new markers for Shallow Benthic zones 19-20

Here, we revise and update the biostratigraphy of larger foraminiferal assemblages in three sections of the Priabonian Sanetsch Formation in the Helvetic Nappes of theWestern Swiss Alps: The SexRouge (SE) and the Sanetsch Buvette (SA) sections in the Wildhorn Nappe Complex, and the Col des Essets (ETS) section in the most external Morcles Nappe. In the SE and SA sections, the Tsanfleuron and most of the Pierredar Limestone members of the formation are assigned to SBZ 19 (early Priabonian), while the uppermost part of the formation is assigned to SBZ 20 (late Priabonian). In the external ETS section the entire Sanetsch Formation contains assemblages characteristic of SBZ 19, suggesting an earlier, middle-late Priabonian onset of the hemipelagic Stad Formation (Globigerina Marls). Since it was established in 1998, the Shallow Benthic Zones (SBZ), a biozonation based on larger foraminifera, has been a useful tool in the biostratigraphy of the Paleogene. Biozonation proposals for the late middle-late Eocene are based mainly in biometrical subdivision of lineages of nummulitids and orthophragmines,which requiresmeasurements in oriented sections of isolated specimens. Here, we define previously unreported taxa from the Sanetsch Formation, which are considered characteristic for the Priabonian. They are easy to identify in random sections and thus useful biostratigraphical markers.We also describe a new orthophragminid genus, Virgasterocylina n. gen. (Orbitoclypeidae) characterized by the presence of rods, radial thickenings of calcite along ribs; a new species of Rotorbinella, R. epardi n. sp., and a new genus and new species of difficult suprageneric attribution, Sanetschella indeprensa n. gen., n. sp. We add the new taxa to the larger foraminiferal association characterizing the Priabonian (SBZ 19-20). The revision of the literature, together with our own sample collections revealed that these new taxa occur in Priabonian rocks from different basins in the western Tethys. Virgasterocylina n. gen. also occurs in the Caribbean bioprovince in the middle and upper Eocene. In the western Tethys, Virgasterocylina ferrandezi is subdivided into two subspecies, V. f. ferrandezi (Ozcan and Less) and V. f. lessi n. ssp., which characterize the SBZ 19 and 20 biozones respectively.

Retrieving planktonic foraminifera from lithified rocks, examples from the Eocene limestones and marls (External Dinarides, Croatia)

Paleoecologic (paleoclimatologic) and biostratigraphic studies of pelagic and deep-water deposits rely on the identification of planktonic foraminifera. Here we report and compare the results of planktonic foraminiferal assemblages from the Middle Eocene indurated limestones and marls collected in the External Dinarides extracted with acetic acid of different concentrations (50%, 60%, 70% and 80%) and different reaction (exposure) times. The deposits originated within the Dinaric foreland basin, have been assigned to the so-called Transitional beds and Flysch, and are characterized by different ratio of carbonate content and degree of lithification. The aim of this paper is to compare the efficiency of the laboratory procedures for obtaining isolated specimens and to evaluate the impact of preparation procedure on the quality of tests (complete test vs. secondary dissolution effects). For each acetic concentration we assessed:(1)the effectiveness of the treatment in terms of the time required for successful extraction of planktonic foraminifera, and(2)the degree of dissolution by analyses of dissolution proxies, including the weight percentage of sieved residues after disaggregation and preservation features of the tests. Our results indicate that accurate taxonomic analysis of carbonate rocks requires the use of 60% acetic acid for a shorter reaction time, and hydrogen peroxide methods for marls.

Intertidal zonation of live benthic foraminiferal assemblages from mangrove environments around south-west Penang Island, Peninsular Malaysia

Abstract Studies on benthic foraminifera were conducted in the mangrove forests of Teluk Tempoyak, Pulau Betong and Kuala Sungai Pinang, Penang Island, Peninsular Malaysia to examine species composition and distribution patterns in different intertidal zones. Twenty-eight live benthic foraminiferal species were successfully identified at the study locations, predominantly species with agglutinated tests. Assemblages in Pulau Betong and Teluk Tempoyak were dominated by similar species such as Ammonia aoteana, Elphidium hispidulum, Elphidium neosimplex and Trochammina inflata, while Kuala Sungai Pinang comprises a high number of Trochammina inflata and Arenoparrella mexicana. Three species, Aubignyna perlucida, Elphidium neosimplex and Elphidium sandiegoense, were recorded for the first time in Malaysian mangrove forests. Principal component analysis showed that sediment type and organic matter content were the dominant parameters that explained the variation of environmental gradient. Canonical correspondence analysis of these parameters with benthic foraminiferal species indicated that sand particles influenced distribution of the hyaline tests. Species with agglutinated tests were abundant in sediment with rich organic matter in combination with high silt and clay content. Species with hyaline tests dominated lower intertidal zones, while those with agglutinated tests inhabited the area from the middle to upper intertidal zones. This distribution pattern of benthic foraminiferal species mirrored patterns found at other local and global mangrove locations.

New biostratigraphy and microfacies analysis of Eocene Jahrum Formation (Shahrekord region, High Zagros, West Iran). A carbonate platform within the Neo-Tethys oceanic realm

The Eocene Jahrum Formation in High Zagros was studied in Kuh-e- Soukhteh and North Gahrou sections (southwest of Shahrekord region, Chahar-mahal Bakhtiari Province). This formation, composed of limestone, marl, and dolomitic limestone (dolostone), accumulated on a marine platform within the Neo-Tethys ocean realm. It yields a rich foraminiferal fauna, in which three larger benthic foraminiferal assemblage zones were identified. Two assemblage zones in the North Gahrou section were correlated to the Ypresian and Bartonian, and one assemblage zone is represented in the Kuh-e- Soukhteh section and assigned to the Bartonian. In addition, three other groups of benthic foraminiferal associations have been identified based on test wall type (porcellaneous, agglutinate, hyaline) and paleogeographical significance. A discontinuity marked by a hiatus from Cuisian to Lutetian in the North Gahrou section was most probably due to a concealed fault. According to microscopic textures and distribution of benthic foraminifera and other components (peloids, intraclasts, etc.), a gentle depth gradient from the inner ramp to the proximal outer ramp may be reconstructed.

Biostratigraphy of larger foraminifera from the Middle Eocene Jahrum-Pabdeh formations (Zagros region, SW Iran) and their correlation with the planktonic foraminiferal zones

Eocene larger benthic foraminifera including orthophragmines, nummulitids and alveolinids from the Jahrum and Pabdeh formations in the Zagros region are presented. The studied 20-m-thick stratigraphic interval contains, Asterocyclina Gumbel 1870, Nemkovella Less 1987, Orbitoclypeus Silvestri 1907, Discocyclina Gumbel 1870, Nummulites Lamarck 1801, Assilina d'Orbigny 1826 and Alveolina d'Orbigny 1826. This larger benthic foraminiferal assemblage testifies for the shallow benthic zones (SBZs) 15 to 17, which ranges from the middle Lutetian up to the early Bartonian. Further micropaleontological analysis made on intercalated planktonic-rich levels helps calibrate the larger foraminifera biostratigraphy, demonstrating a correlation with the E11 biozone. This confirms that the chronostratigraphic calibration of the SBZs made by previous authors for the peri-Mediterranean area can, through the middle Lutetian to the early Bartonian, be applicable in the Middle East as well.

Foraminifera of the Eocene Shitakara Formation in eastern Hokkaido, with the designation of neotype specimens of Yoshida (1957)

Forty-three species belonging to thirty-seven genera of benthic foraminifera were differentiated from the Eocene Shitakara Formation in the eastern part of the Kushiro Coalfield, eastern Hokkaido. The foraminiferal assemblages show upward transgression from the inner to outer sublittoral condition. They contain abundant agglutinated and calcareous hyaline benthic species, including Labrospira crassiformis, Haplophragmoides subamakusaensis, and Cribroelphidium sorachiense, indicating similarity to the Eocene fauna in central Hokkaido. Two planktonic species Chiloguembelina ototara and Tenuitella insolita also indicate a late Eocene age. Neotype specimens of Cyclammina pacifica var. kushiroensis, Nonion kushiroense, and Nonion sorachiense var. konbumoriense described by Yoshida (1957) have been designated as replacements for holotype specimens that were lost in a fire in May 1965. A taxonomical reexamination based on the neotypes and topotypes indicates that Cyclammina pacifica var. kushiroensis is a distinct species, whereas Nonion kushiroense and Nonion sorachiense var. konbumoriense are junior synonyms of Cribroelphidium sorachiense (Asano 1954). All foraminiferal taxa are illustrated with taxonomical notes.

SIX-CHAMBERED VOLUTION OF THE MAASTRICHTIAN PLANKTIC FORAMINIFERAL PLUMMERITA SPECIES IN THE TETHYS

Brönnimann (1952), from Trinidad, was distinguished the last six-chambered volition of the genus Rugoglobigerina (R. reicheli, R. pustulata, R. hexacamerata) as a separate group from another last five-chambered volition with spine-like prolongation of ultimate and penultimate chambers Plummerita hantkeninoides group (P. hantkeninoides, P. costata, P. inflata). Later on, the Rugoglobigerina reicheli specimen belongs to the genus Plummerita due to its spine-like prolongation of ultimate and penultimate chambers, while the other two species R. hexacamerata and R. pustulata don’t have these distinguished characters of the genus Plummerita. In this study, added to P. reicheli of Brönnimann, three new species of the planktic foraminiferal assemblage of six-chamber volution of the Plummerita reicheli group are presented: Plummerita reicheli (Trinidad), P. caribbeanica (Porto Rico). P. spainica (Spain) and P. tunisica (Tunisia).

Shelf inhabiting foraminifera as a tool for understanding late quaternary mass transport processes in the Northern Gulf of Eilat/Aqaba, Red Sea

Sedimentary systems on continental margins are sensitive to climate change and sea level fluctuations, especially in tectonically active areas as the Gulf of Eilat/Aqaba (GEA). During the Late Quaternary, in addition to the repetitive seismic activity along the Dead Sea Transform, drastic changes in sea level, temperature and salinity occurred in the marine environment resulting in changes of the faunal community. In this study, a newly established approach, using the depth distribution of foraminifera to identify displaced sediment units, is utilized to reconstruct the events, which occurred in this rapidly changing environment. A total of 11 units of displaced sediments and 3 temporally significant unconformities were identified based on foraminiferal assemblages and time constrained by radiocarbon dating. These were identified within two cores from the GEA northwestern slope at water depth of 300–400 m, covering up to 40 kyr BP. Two foraminiferal assemblages were identified corresponding with the changing salinity: 1) the ‘Holocene assemblage’ dominated by the stenohaline symbiont-bearing larger species Operculina ammonoides, Amphistegina papillosa and Amphistegina bicirculata; and 2) the ‘Glacial assemblage’ dominated by the hypersaline tolerant species Elphidium cf. limbatum, Elphidium jenseni and Peneroplis planatus. Both assemblages were found in deeper settings than their natural living habitat, indicating the presence of sediment transport down slope, and suggesting benthic foraminifera can serve as an indicator for sediment transport events. Unconformities were found to be associated with periods of rapid sea level changes and/or increased sedimentation rates, effecting sediment porosity and slope stability. Displaced shells of the ‘Holocene assemblage’ were dated to 12 kyr BP and believed to be the first recorded evidence for the post glacial re-settlement of this ecologically important group in the northern GEA.

Sedimentary records and implications for the evolution of sedimentary environments inferred from BH1302 during the late Quaternary in the Bohai Sea, China

Under the influence of glacial-interglacial climate change and regional tectonic activities in the Quaternary, the sedimentary environments of the Bohai Sea changed greatly, providing significant information on transgression-regression events, East Asian monsoon changes and regional tectonic activities. This study analyzed the sedimentological characteristics of the BH1302 core (water depth of 12.3 m, length of 70.2 m) in the southern Bohai Sea based on grain size, foraminiferal assemblages, carbon and oxygen isotopes in foraminiferal shells and element geochemistry, and established a chronological framework based on AMS 14C, optically stimulated luminescence dating and Oxcal age-depth model using Bayesian modeling. The results showed that three interglacial transgressions and one interstadial transgression were revealed in BH1302 since the late Quaternary, corresponding to marine isotope stages (MIS) 7, 5, 3 and 1, and three subinterglacial transgressions were further identified during MIS 7. The sedimentary environments of Laizhou Bay transitioned from an estuary environment dominated by rivers to a neritic environment dominated by marine conditions because of subsidence of the Miaodao uplift in late MIS 7.1. Three subinterglacial transgressions occurred in MIS5 and two subinterstadial transgressions in MIS 3, and the highstand sea level of MIS 3 reached approximately −18 ∼ −21 m. Under the influence of sea level fluctuations and the East Asian monsoon, the sedimentary environments of MIS 1 can be divided into a low salinity tidal-flat environment (12.0–7.0 kyr BP), a low salinity neritic environment (7.0–4.5 kyr BP) and a modern neritic environment (∼4.5 kyr BP).

Latest Hauterivian foraminiferal and calcareous nannofossil assemblages and bioevents from the Pseudothurmannia beds (Central Western Carpathians, Slovakia): A prelude to the Faraoni event

A diverse and abundant assemblage of deep-water agglutinated foraminifera (DWAF) has been recovered from an uppermost Hauterivian ammonite-rich horizon (Pseudothurmannia ohmi Biozone) from the Central Western Carpathians. The section records the last occurrence of the calcareous nannofossil species Litraphidites bollii (Thierstein) preceding the Faraoni anoxic level. Various morphogroups of agglutinated foraminifera show changes in response to trophic regime shift and decreasing oxygenation of the bottom and pore waters in a relatively short time-series. The DWAF data were compared with calcareous nannofossil assemblages and foraminifera analysed from thin sections (calcareous benthic and planktonic foraminifera). Four ecozones were identified, each with a specific taxonomic composition of foraminiferal assemblages. The zone-to-zone changes include fluctuations in the richness and relative abundance of morphogroups and planktonic foraminifera, and dwarfism in certain groups of foraminifera.

New larger benthic foraminifera from the subsurface Lower to Middle Eocene Oldsmar Formation of southeastern Florida (USA)

We describe two larger benthic foraminiferal taxa collected from wells drilled in the subsurface Eocene rocks of southeastern Florida that are new to peninsular Florida and the Caribbean region. Saudia floridana n.sp. is characteristic of a foraminiferal assemblage, along with Helicostegina gyralis, wide forms of the Cushmania americana group, and Gunteria floridana, in an upper part of the Oldsmar Formation. Globogypsinoides browardensis n.gen. n.sp. occurs in a second foraminiferal assemblage, along with Borelis cf. floridanus, Coskinolina cf. yucatanensis, and as-yet undescribed large rotaliids, in a middle part of the Oldsmar Formation. The foraminiferal assemblage of the middle Oldsmar unit is ascribed an Ypresian age and the assemblage of the upper Oldsmar unit a Lutetian age. These two assemblages indicate inner shelf water depths of 40 m or less on the Florida Platform during the Early to Middle Eocene deposition of the middle to upper part of the Oldsmar Formation.

Spatial Distribution of Benthic Foraminifera in the Neretva Channel (Croatia Coast): Faunal Response to Environmental Parameters

Benthic foraminiferal assemblages have been studied at 11 sediment surface samples located in the Neretva Channel covering the delta habitat and the adjacent open sea areas. The major objective of the investigation was to explore the main environmental parameters affecting the benthic foraminifera compositional changes. To this end, a statistical approach was applied that integrates micropaleontological data with physical, geochemical and sedimentological parameters (total organic carbon and grain size). Statistical analyses identified four distinct groups (cluster A1, A2, B1, B2) corresponding to different environmental settings. Cluster A1 groups samples under Neretva river influence and is characterized by Aubignyna perlucida, Nonionella turgida, Eggerelloides scaber and Rectuvigerina sp.; species able to live in organic-matter-rich sediments and in a wide range of oxygen content. Cluster A2 includes samples distant from the fluvial outlet and samples along the NW coast partially influenced by the Neretva river plume. In these environmental conditions, Ammonia beccarii, Bulimina marginata, Nonionella turgida and Textularia sp. resulted as the most characteristic taxa. Cluster B1 distinguishes the deepest stations which are in connection with the open Adriatic Sea. Here Asterigerinata mamilla, Buccella granulata, Cibicides group, Reussella spinulosa and Textularia sp. reach their maximum abundance associated with coarse-grained sediments. Cluster B2 groups samples collected in the inner bay of the southernmost sector of the studied area characterized by silt and clay and a negligible influence by river inputs. The benthic microfauna is principally composed of Miliolids, Porosononion granosum and Textularia sp.