Abundance Of Planktonic Foraminifera Research Articles

Seasonal and vertical distribution of living planktonic foraminifera in the western tropical Pacific Ocean

To investigate the seasonal and vertical distributions of planktonic foraminiferal species in the western tropical Pacific Ocean, we collected planktonic foraminifera seasonally and diurnally from eight water depths from 0 to 600 m using the Multiple Opening/Closing Net and Environmental Sensing System. We identified 23 living foraminiferal species (size fraction 212–1000 μm) and examined their abundances at the sites of oligotrophic areas. Seasonal changes were characterized by an increase in the diversity and abundance of planktonic foraminifera in summer. We estimated the habitat depth of planktonic foraminifera based on their vertical distribution. Planktonic foraminifera can be classified into species living in the surface mixed layer, uppermost thermocline, upper thermocline, and lower thermocline in the water column. The uppermost thermocline layer is characterized by the occurrence of subsurface chlorophyll maximum (water depth, 100–150 m). The boundary between the upper and lower thermocline layers (approximately 300 m) is at the depth at which the dissolved oxygen concentration begins to rapidly decrease. The species inhabiting the surface mixed layer were Globigerinoides sacculifer and Globigerinoides ruber white in spring. In summer, G. sacculifer dwelled in the surface mixed layer during night time, whereas they existed in the uppermost thermocline during daytime. Many species were found in the uppermost thermocline layer in summer, including G. ruber white, Globigerinoides conglobatus, Globigerinella siphonifera, Pulleniatina obliquiloculata, Globoquadrina conglomerata, Orbulina universa, Neogloboquadrina dutertrei, Globigerinella calida, and Hastigerina pelagica. The species Globorotalia hirsuta dwelled in the upper thermocline in spring, whereas it occurred in the lower thermocline in summer. Globorotaloides hexagonus inhabited the lower thermocline in all seasons. Our results will provide useful information for reconstructing changes in water column structure using planktonic foraminiferal shells in marine sediments.

Deep-sea paleoenvironmental evolution in the mid-Cretaceous of the Basque Pyrenees based on microfaunal analysis (Armintza section)

The mid-Cretaceous Black Flysch Group and Plentzia Formation constitute two key lithostratigraphic units in the evolution of the Pyrenean rift system but many of their paleoenvironmental characteristics are poorly known. In this work, a microfaunal analysis (planktonic and benthic foraminifera and ostracods) of these two units at the Armintza section has been carried out in order to interpret the paleoenvironmental conditions (paleodepth, oxygen level and water masses) in which they deposited, and to relate them to the contemporary tectono-sedimentary settings. Based on the high proportion of planktonic foraminifera with respect to total foraminifera and the assemblages of benthic foraminifera species, a paleodepth of ∼600 m is estimated for studied units. During syn-rift deposition of the organic-rich Black Flysch Gp. in middle Albian-early Cenomanian times, the relative abundance of planktonic foraminifera and the proportions of different shell morphotypes suggest the presence of a shallow water mass and the stagnation of deeper waters. Moreover, the presence of abundant hypoxia-tolerant benthic foraminifera species and the occurrence of only rare hypoxia-tolerant platycopid ostracods indicate severe hypoxia conditions (<1.5 ml/l) or even anoxia at the seafloor. A noticeable change is recorded at the contact between the Black Flysch Gp. and the Plentzia Fm. (lower-middle Cenomanian transition). During post-rift deposition of the Plentzia Fm. in earliest middle Cenomanian times, developed microfaunal assemblage shows an important increase in benthic foraminifera species, many of which indicate intermediate waters, and dominance of keeled planktonic foraminifera suggesting the end of water stagnation and the inflow of an intermediate water mass. In addition, the presence of hypoxia-tolerant species of ostracods and benthic foraminifera indicates the development of mild hypoxia conditions at the seafloor during this interval.

Planktonic foraminiferal assemblages reflect warming during two recent mid-latitude marine heatwaves

Under future climate scenarios, ocean temperatures that are presently extreme and qualify as marine heatwaves (MHW) are forecasted to increase in frequency and intensity, but little is known about the impact of these events on one of the most common paleoproxies, planktonic foraminifera. Planktonic foraminifera are globally ubiquitous, shelled marine protists. Their abundances and geochemistry vary with ocean conditions and fossil specimens are commonly used to reconstruct ancient ocean conditions. Planktonic foraminiferal assemblages are known to vary globally with sea surface temperature, primary productivity, and other hydrographic conditions, but have not been studied in the context of mid-latitude MHWs. For this study, the community composition and abundance of planktonic foraminifera were quantified for 2010-2019 along the Newport Hydrographic Line, a long-term monitoring transect at 44.6°N in the Northern California Current (NCC). Samples were obtained from archived plankton tows spanning 46 to 370 km offshore during annual autumn (August – October) cruises. Two MHWs impacted the region during this timeframe: the first during 2014-2016 and a second, shorter duration MHW in 2019. During the 2014-2016 MHW, warm water subtropical and tropical foraminifera species were more prevalent than the typical polar, subpolar, and transitional species common to this region. Cold water species were abundant again after the first MHW dissipated in late 2016. During the second, shorter-duration MHW in 2019, the assemblage consisted of a warm water assemblage but did not include tropical species. The foraminiferal assemblage variability correlated with changes in temperature and salinity in the upper 100 meters and was not correlated with distance offshore or upwelling. These results suggest that fossil foraminiferal assemblages from deep sea sediment cores may provide insight into the magnitude and frequency of past MHWs.

Sedimentary and Diagenetic Controls across the Cretaceous—Paleogene Transition: New Paleoenvironmental Insights of the External Ionian Zone from the Pelagic Carbonates of the Gardiki Section (Epirus, Western Greece)

Field investigation, biostratigraphic, paleoecological, and sedimentary microfacies analyses, as well as diagenetic processes characterization, were carried out in the Epirus region (Western Ionian Basin) to define the depositional environments and further decipher the diagenetic history of the Late Cretaceous–Early Paleocene carbonate succession in western continental Greece. Planktonic foraminiferal biostratigraphy of the studied carbonates revealed that the investigated part of the Gardiki section covers the Cretaceous–Paleogene (K-Pg) transition, partly reflecting the Senonian limestone and calciturbidites formations of the Ionian zone stratigraphy. Litho-and bio-facies analyses allowed for the recognition of three distinct depositional facies: (a) the latest Maastrichtian pelagic biomicrite mudstone with in situ planktonic foraminifera, radiolarians, and filaments, (b) a pelagic biomicrite packstone with abundant planktonic foraminifera at the K-Pg boundary, and (c) an early Paleocene pelagic biomicrite wackestone with veins, micritized radiolarians, and mixed planktonic fauna in terms of in situ and reworked (aberrant or broken) planktonic foraminifera. The documented sedimentary facies characterize a relatively low to medium energy deep environment, representing the transition from the deep basin to the deep shelf and the toe of the slope crossing the K-Pg boundary. Micropaleontological and paleoecological analyses of the samples demonstrate that primary productivity collapse is a key proximate cause of this extinction event. Additional petrographic analyses showed that the petrophysical behavior and reservoir characteristics of the study deposits are controlled by the depositional environment (marine, meteoric, and burial diagenetic) and further influenced by diagenetic processes such as micritization, compaction, cementation, dissolution, and fracturing.

S/SE Brazilian continental margin sea surface temperature and productivity changes over the last 50 kyr

Off the S/SE Brazilian continental margin, the Brazil Current (BC) drives important oceanographic processes. Over the Deglacial time interval, this shallow current was influenced by the Atlantic Meridional Overturning Circulation (AMOC) at different timescales resulting in changes in sea surface temperature (SST) and primary productivity. In this work, a 50-kyr record retrieved from the upper slope of Santos Basin (NAP63–1, 24°30′10“ S, 44°11’28” W, 842 m) was utilized to evaluate SST and productivity changes based on planktonic foraminifera abundances and Globigerinoides ruber (albus) Mg/Ca ratios. Our results highlight that during Marine Isotopic Stage 3 (MIS 3), the SW Atlantic was marked by increased variability in SST and productivity related to South Atlantic Central Water upwelling during BC strengthening driven by episodic AMOC interruption events. As the AMOC weakened during MIS 2, the BC strengthened, and surface water productivity increased in the Brazilian margin. Towards MIS 1, SST progressively increased while productivity decreased because of a weaker BC as AMOC resumed its interglacial state. Our findings suggest that the previously observed Holocene antiphase relationship between AMOC and BC has been present since MIS 3.

Calcification, Dissolution and Test Properties of Modern Planktonic Foraminifera From the Central Atlantic Ocean

The mass of well-preserved calcite in planktonic foraminifera shells provides an indication of the calcification potential of the surface ocean. Here we report the shell weight of 8 different abundant planktonic foraminifera species from a set of core-top sediments along the Mid-Atlantic Ridge. The analyses showed that near the equator, foraminifera shells of equivalent size weigh on average 1/3 less than those from the middle latitudes. The carbonate preservation state of the samples was assessed by high resolution X-ray microcomputed tomographic analyses of Globigerinoides ruber and Globorotalia truncatulinoides specimens. The specimen preservation was deemed good and does not overall explain the observed shell mass variations. However, G. ruber shell weights might be to some extent compromised by residual fine debris internal contamination. Deep dwelling species possess heavier tests than their surface-dwelling counterparts, suggesting that the weight of the foraminifera shells changes as a function of the depth habitat. Ambient seawater carbonate chemistry of declining carbonate ion concentration with depth cannot account for this interspecies difference. The results suggest a depth regulating function for plankton calcification, which is not dictated by water column acidity.

Abrupt changes in the southwest monsoon during Mid-Late Holocene in the western Bay of Bengal

• Variation in southwest monsoon governs the surface circulation of Bay of Bengal. • Reduction in fresh water flux between ∼5.9 and ∼3.7 kyr. • A progressive increase in fresh water flux after ∼3.7 kyr. • Abrupt increase in fresh water flux related to RWP and MWP extreme events. The present work aims to understand the variation in the southwest monsoon (SWM) and the surface water hydrography around the western Bay of Bengal (WBoB). In this study, we used various micropaleontological [planktonic foraminifera relative abundance, planktonic and benthic foraminiferal abundance (PFA and BFA), planktonic/benthic (P/B) ratio], sedimentological [sand %] and oxygen isotope of Globigerinoides ruber (δ 18 O G.ruber ) proxies in a marine sediment core (SK336/3) since last ∼6 kyr before present (BP). The δ 18 O G.ruber , PFA, BFA, and the planktonic foraminifera relative abundance records suggest the reduced freshwater input corresponding to an aridification phase during ∼5.9–3.7 kyr BP, possibly related to the weakening of the SWM in the WBoB. The WBoB has reworded comparatively wetter conditions since ∼3.7 kyr BP suggests increased freshwater input centering around ∼1.8 and ∼0.9 kyr BP, associated with the SWM intensification during the Roman and Medieval Warm Periods (RWP and MWP), respectively. The relative abundance of planktonic foraminifera correlates well with a sand percentage between ∼5.9 and ∼3.7 kyr BP, suggesting a productivity decline due to terrigenous dilution. Significant periodicities of ∼418, ∼165, ∼139, ∼109, ∼97, and ∼86 years are found in the spectral analysis of planktonic foraminiferal relative abundance and δ 18 O G.ruber time-series, corresponding to hydrographic changes in the WBoB due to the influence of solar-driven cyclicity in the SWM during the last ∼6 kyr BP. Comparison of our multi-proxy signatures with other paleo-proxy records during the mid-late Holocene reveals large-scale climate variability in the Northern Hemisphere, related to the changes in solar activity.

A Preliminary Study In Vertical Distribution Of Planktonic Foraminifera And Marine Ecological Conditions Of Simeulue Sub-Basin, Aceh, Indonesia

A marine sediment core EW17-09 (03˚ 28’358” latitude and 96˚ 18’788” longitude, 870 m water depth, 390 cm core length) was retrieved from the western Sumatra, Simeulue sub-basin, Indonesia. Simeulue sub-basin are situated in eastern Indian Ocean, western part of Aceh Province, which is one of the outer islands in Indonesia. This sub-basin is influenced by adjacent lands in response to tectonic and climate dynamics. The dynamics of marine ecological conditions in the past is an urgent need for providing an analogy to the changes in the future conditions. In this study, the ecological conditions were examined by identifying the vertical distribution of planktonic foraminifera assemblages. This preliminary study demonstrated the presence of Globigerinoides ruber, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, Globigerina calida calida, Globigerinoides elongates, Globigerinoides cyclostomus and Globigerinoides sacculiferus in the samples. The assemblages indicate warm water conditions prevailed in the Simeulue sub-basin during the deposition of the samples. However, subtle ecological changes might have occurred in response to the dynamic of thermocline layer. Cluster analysis of planktonic foraminifera abundance and diversity resulted in three groups showing different ecological conditions. Warm water conditions, high salinity, deeper thermocline with moderate sedimentation disturbance prevailed during the deposition of lower part of the core. Oligotropic water conditions with higher temperature, lower salinity, shallower thermocline layer, and moderate sedimentation disturbance predominated during the deposition of the middle part of the core. The paleooceanography conditions of the upper part of the core are comparable to the lower part. Nevertheless, there are a shoaling of the thermocline in the end of the period. These conditions may indicate an increase in upwelling fluctuations and may represent a change in the IOD-like mean state of the Indian Ocean.

Using microplankton proxies to evaluate marine palaeonvironmental changes during late Maastrichtian: Evidence from the Møre Basin (Norwegian continental shelf)

This work presents high-resolution palynological and micropalaeontological analyses of a cored succession across the upper Maastrichtian from a well in the Møre Basin (Norwegian continental shelf). Diverse assemblages of dinoflagellate cysts and foraminifera provide insights into the palaeobiogeography and palaeoenvironmental conditions during the late Maastrichtian in this region. An outer neritic setting is interpreted based on the general high abundance of planktonic foraminifera. A subdivision of the biostratigraphic record into three Ecozones has allowed for a detailed documentation of the phytoplankton communities during the late Maastrichtian until the K-Pg boundary. Ecozone A is characterised by a predominance of peridinoid cysts which together with abrupt fluctuations in planktonic foraminifera suggests high nutrient availability and, possibly, high terrestrial input potentially associated with regional turbiditic currents. Also, the occurrence of taxa characteristic of boreal affinity suggests colder waters for this Ecozone. Ecozone B is characterised by consecutive influxes of areoligeracean species such as Palynodinium grallator, Areoligera senonensis and Circulodinium distinctum in the dinoflagellate cyst assemblages. The increase abundances of planktonic foraminifera across this interval suggests an increase in palaeowater depth into a more outer shelf to upper slope. Immediately before the K-Pg boundary (Ecozone C), an increase in abundance of low latitude dinoflagellate species and the planktonic foraminifera Pseudotextularia elegans may represent the local signal of the global latest Maastrichtian Warming Event. Two new dinoflagellate cyst species restricted to the late Maastrichtian, Glaphyrocysta turgida sp. nov. and Heterosphaeridium silybum sp. nov. are also formally described.

Strontium isotopes and planktonic foraminiferal biostratigraphy of Eocene carbonate rocks from the Adıyaman–Malatya vicinity (southeast Turkey) and chronostratigraphic implications

Cenozoic sediments are spread across southeast and eastern Anatolia, including the Adıyaman–Malatya regions of southeast Turkey. This study presents the first detailed petrographic, micropaleontologic, and strontium isotope analyses of the Eocene marl, clayey limestone, and limestone units that outcrop unconformably above the Mesozoic Meydan and İspendere ophiolitic rocks in the Adıyaman and Malatya regions, respectively. These carbonate rocks contain abundant planktonic foraminifera, including Turborotalia frontosa, Subbotina senni, Subbotina eocaena, Acarinina bullbrooki, Guembelitrioides nuttalli, Globigerinatheka subconglobata, and G. curryi, and benthic taxa (Nummulites, Discocyclina, and Chapmanina).Two planktonic foraminiferal zones were defined: the Turborotalia frontosa zone representing the Early–Middle Eocene (Ypresian–Lutetian/Bartonian), and the Turborotalia possagnoensis zone representing the Middle Eocene (Lutetian–Bartonian). Strontium isotope ratios (87Sr/86Sr) calculated for four samples ranged between 0.707663 and 0.707784, indicating an age of 45.1–51.9 million years (Ypresian–Lutetian/Bartonian). The presence of echinoid thorns in the units indicates a shallow marine environment where carbonates developed on the seaward side of a reef. For the first time in the study region and southeast Anatolia, this study has revealed the stratigraphic position of the Nummulitic limestone of the Kırkgeçit Formation unconformably overlying the ophiolites. Therefore, based on strontium isotope analyses and planktonic foraminiferal micropaleontology, the Kırkgeçit Formation is estimated as Early–Middle Eocene (Ypresian–Lutetian/Bartonian) in age.

Biostratigraphy and depositional environments of the Palaeocene–Eocene succession at Um El Huwaitat area, Eastern Desert, Egypt

The Palaeocene–Eocene succession in southwest Safaga, Eastern Desert, Egypt has been studied to determine its lithostratigraphic units, biostratigraphic zonation, microfacies association, and depositional environments. The variation in lithofacies allows the subdivision of the Danian–Ypresian interval into four lithostratigraphic units that are arranged, from base to top, as the Dakhla Shale (only its upper part), Tarawan Chalk, Esna Shale, and Thebes Formation (only its lower part). Moreover, the Esna Shale is further subdivided into four members, arranged from base to top, as El Hanadi, Dababiya Quarry, El Mahmiya, and Abu Had. The depositional setting is interpreted to primarily reflect the relative sea‐level changes. The planktonic/benthic (P/B) foraminiferal ratio is indicative of oscillations of depositional settings in normal open marine conditions, ranging from shallow inner to outer neritic environments. Biostratigraphically, the Palaeocene–Eocene succession in the studied area is subdivided into 12 biozones and subbiozones. These are correlated with the standard biozonation of the Palaeocene–Eocene. Deposition of the Palaeocene–Eocene succession in the studied area took place on a relatively stable shelf. Three lithofacies were recognized: shale, marl, and limestone. The shale lithofacies is differentiated into two sub‐lithofacies; pure shale and calcareous foraminiferal shale, whereas marl lithofacies contains abundant planktonic foraminifera. The encountered carbonate rocks comprise eight microfacies types. In addition, the studied interval is correlated with the Global Standard Stratotype Section and Point in the Dababiya section, south of Luxor, Egypt.

Variable Kuroshio Current intrusion into the northern South China Sea over the last 7.3 kyr

The branch intrusion of the Kuroshio Current (KC) into the northern South China Sea (SCS) has a significant effect on temperature, salinity, circulation, and eddy generation. However, the study of Holocene hydrological changes and the historical influence of the KC in this region is limited. Here, we report high-resolution sea surface temperature (SST) and δ18Osw (as a proxy for sea surface salinity, SSS) records based on paired Mg/Ca ratios and δ18O analyses of the planktonic foraminifera Globigerinoides ruber combined the Pulleniatina obliquiloculata and G. sacculifer/G. ruber ratios from core 05E306 (22°0.06′ N, 118°59.64′ E; water depth = 1440 m) in the northern SCS. By comparing these data with records from cores located within and outside of the main KC flow pathway, we evaluate the spatiotemporal evolution of the KC in this region over the last 7.3 kyr. The strongest influence was observed from 6.1 to 5.3 ka, recorded as an abrupt increase in SST and SSS with remarkably increased P. obliquiloculata abundance (37.4%) and G. sacculifer/G. ruber ratios (3.18). During the following period, 5–2.5 ka, SST decreased by 0.4–1.1 °C with an associated decrease in δ18Osw, indicating a weakened KC. After 2.5 ka, the influence of the KC on the northern SCS strengthened; however, the high SST record still exhibits a spatial constraint in the longitude distribution of the KC during this period of strongest intrusion. Moreover, the abundance of planktonic foraminifera in the study area more strongly correlates with SSS than SST. The δ18Osw records in core 05E306 show a freshening trend after 5.7 ka, which is inconsistent with the declining East Asian Summer Monsoon precipitation record but consistent with the Holocene freshening trend recorded in the Western Pacific. This suggests that hydrological variability of the northern SCS is mainly influenced by the Western Pacific Ocean.

Changes in sea surface hydrography and productivity in the western equatorial Atlantic since the last interglacial

Scientific projections point to the increase of greenhouse gas levels in the atmosphere will turn the oceans warmer and, consequently, the upper layer of the thermohaline circulation will get thicker, restricting the productivity areas. Oligotrophic conditions will tend to prevail, and expanding the range of proxy data in oligotrophic oceans, across different climate scenarios, has the potential to improve predictions of climate models about how primary productivity will respond. Still, the variability of past primary production in the equatorial Atlantic remains elusive. We used organic-walled dinoflagellate cysts (dinocysts) assemblages to reconstruct changes in the sea surface hydrography and productivity in the western equatorial Atlantic over the last ~130 kyr. Four dinocysts assemblages were defined: open ocean, river outflow, neritic and nutricline assemblages. Multiple proxies were used to support the environmental changes evidenced by the observed variations in the dinocyst assemblages, such as the X-ray fluorescence (XRF) Ti/Ca ratio, and planktonic foraminifera abundances. We observed glacial-interglacial as well as the millennial-scale changes in the dinocyst assemblages. A clear glacial-interglacial pattern was marked by more autotrophs dinocysts over the interglacials and the prevalence of heterotrophs dinocysts during the glacial period. We pointed out the interchange of autotrophs assemblages (nutricline and open ocean) over the interglacials intervals, denoting divergences in nutrient availability. During the last glacial period, precipitation events occurred in northeastern Brazil due to southward displacements of the Intertropical Convergence Zone (ITCZ). The increase of precipitation boosted the freshwater input to the adjacent ocean, and the dinocyst assemblages oscillated in response to such freshwater/salinity changes. Over the glacial period, dinocysts with different nutritional requirements (autotrophs and heterotrophs) varied following the ITCZ displacements. Thus, in this study, we showed the influence of ocean-atmospheric processes on the ocean and investigated the productivity in an oligotrophic region over distinct past climatic backgrounds.

Sedimentary response to sea level and climate changes in the inner sea of Maldives carbonate platform over the past 30 kyr

We applied AMS 14C dates, Mg/Ca estimated sea surface temperature (SST), planktonic foraminiferal abundance, coarse component and X-ray diffraction mineral composition analyses for an International Ocean Discovery Program (IODP) sediment Hole U1467C in the Maldives inner sea, to reveal factors that affected the depositional process in the Maldives inner sea over the past 30 kyr. We found that the linear sedimentation rate (LSR) in Holocene (6.8 cm/kyr) was obviously higher than that in glacial period (3.45 cm/kyr); the average SST during the Holocene was 2–3°C higher than that in glacial stage. High abundance of planktonic foraminifera occurred during the glacial period, which was consistent with the variation of pelagic biogenic component. Reef-sourced material showed apparent high percentage during the Holocene (43.5%), in contrast to the low values during the glacial stage (20.7%). Terrigenous matter, only accounting for a small percentage in carbonate platform, was relatively high during the glacial period than that in the Holocene. We therefore conclude that reef-sourced material, dominated in the glacial-interglacial sediment sources, was mainly affected by sea level and climate changes. During glacial stage, sea level low-stand and weakened weathering in Maldives limited the input of the eroded material into the inner sea, resulting in low LSR; while the Holocene high sea level accompanied with rapid growth of the reef atoll and enhanced weathering, brought more reef-sourced material to the inner sea, leading to increased LSR and lowered abundance of planktonic foraminifera. The sea level and climate-controlled reef-sourced material changes are the key to understand the sedimentary process of the Maldives inner sea. Our study will shed some light on the evolution of glacial-interglacial sedimentary process of carbonate platform.

Reassessment of the age and depositional environments of the Eocene Çayraz Formation, a reference unit for Tethyan larger benthic foraminifera (Haymana Basin, central Turkey)

The Çayraz Formation, a reference unit for Tethyan Ypresian-middle/late Lutetian larger benthic foraminifera (Haymana Basin, central Turkey), is a thick (>350 m) ‘shallow-marine’ mixed carbonate-siliciclastic sequence, divided into lower, middle and upper units. The lower and upper units predominantly consist of rhythmic intercalations of limestone and marly/silty beds with abundant larger benthic foraminifera (LBF), and the middle unit is composed of massive fine siliciclastic sediments, mostly barren in LBF and macrofossils. By studying three sections (ÇAYA, ÇAYB, and YEŞ), encompassing the lower unit, we show that the Çayraz Formation (ca. 100 m-thick) displays notable vertical and lateral variability in benthic fauna and facies along an SE-NW transect at its type locality near Çayraz village. The distribution of LBF and facies patterns indicate a general shallowing upward trend, with more open marine environments in the easterly section (ÇAYA) and restricted shallow marine to continental environments with low diversity fauna in the westerly section (YEŞ). A depositional setting ranging from outer to inner-ramp with continental influence only in the westerly section is proposed. Key orthophragminid and alveolinid taxa from the lower unit of the Çayraz Formation indicate shallow benthic zones (SBZ) 9/10 for its lower part, and SBZ 12 for its upper part, suggesting a late Ypresian age. The massive marly/silty section of the middle unit of the Çayraz Formation overlies the Alveolina-bearing limestones in all sections and yielded abundant planktonic foraminifera suggestive of P9 Zone. This implies a sharp environmental transition from platform to basin across the Ypresian-Lutetian boundary.

Biostratigraphy and paleoenvironments of the Oligocene succession(İhsaniye Formation) at Karaburun (NW Turkey)

The biostratigraphy and paleoenvironments of the Ihsaniye Formation exposed at Karaburun in northwest Turkey is described based upon the study of abundant and well-preserved foraminifera, calcareous nannofossils and palynomorphs. The studied succession is Early Oligocene in age, with calcareous nannofossil zones upper NP21 (Subzone CNO1) to lower NP23 (Subzone CNO3) and planktonic foraminifera zones O1 (~P18) and O2 (~P19) represented, and palynological assemblages suggestive of zones D13 to D14a. Based on these new data, a revised interpretation of the stratigraphic succession is presented. Deposition was controlled by a now inverted normal fault, with deposition of older stratigraphy (upper NP21 to NP22) restricted to the original hanging wall. During NP23, deposition commenced on the footwall, resulting in progressive onlap of an exposed Eocene reefal limestone (Sogucak Formation). Three primary sedimentary facies are present: marls with thin calcareous siltstones, marls with synsedimentary slumps and debris flows, and coarse pebbly sandstones. The coarse pebbly sandstones were deposited in a fan-delta/shoreface paleoenvironment and represent the initial phase of onlap during biozone NP23 onto a rocky shoreline on the footwall side of the fault. The marl-dominated facies represent deposition in outer shelf?upper bathyal environments. The succession demonstrates evidence for a near-end Eocene relative sea-level fall. Changes in the abundance of planktonic foraminifera and the onlap onto the footwall demonstrate maximum subsequent transgression within NP23. This reflects eustasy rather than Paratethyan relative sea-level. No interpretation of sea-water salinity reduction can be made for the sediments deposited during biozone NP23 in the studied sections, although this is noted in coeval sediments in parts of Paratethys (the Solenovian Event). Together with the open marine nature of the diverse and abundant fossil assemblages, it is suggested that deposition of the Karaburun section was strongly influenced by a connection to the global ocean, via the Catalca Gap, as suggested in a recent study.

Latest Priabonian larger benthic foraminiferal assemblages at the demise of theSoğucak Carbonate Platform (Thrace Basin and Black Sea shelf, NW Turkey): implications for the shallow marine biostratigraphy

The Eocene-Oligocene transition corresponds to a significant biotic turnover globally. In shallow marine realms, the larger benthic foraminifera (LBF) belonging to most nummulitids and all orthophragminids became extinct at or near the Eocene/Oligocene boundary, reflecting the environmental deterioration. We here record the advanced developmental stages of midlatitude LBF from the Soğucak Carbonate Platform in NW Turkey on the brink of their extinction in the Tethys. The LBF assemblages in the uppermost part of the platform, exposed in Gökçetepe and Karaburun in the Thrace Basin and Black Sea shelf, are represented by the dominant occurrence of Heterostegina d'Orbigny, 1826, Spiroclypeus Douville, 1905, Operculina d'Orbigny, 1826, Discocyclina Gümbel, 1870, Nemkovella Less, 1987, Orbitoclypeus Silvestri, 1907, Asterocyclina Gümbel, 1870, and subordinate Assilina d'Orbigny, 1826, Nummulites Lamarck, 1801, and Pellatispira Boussac, 1906, characterizing shallow benthic zone (SBZ) 20. In general, the occurrence of Heterostegina, Spiroclypeus, Orbitoclypeus, and Asterocyclina in both sections suggests a deep environmental setting in the shelf. This interpretation is also supported by the presence of abundant planktonic foraminifera in Gökçetepe and the rareness of Nummulites and Assilina in both localities. The cooccurrence of Heterostegina reticulata and H. gracilis in Gökçetepe suggests a stratigraphic position in the lower part of SBZ 20, while in the absence of H. reticulata, Karaburun samples are referred to the upper part of the same biostratigraphic zone. Spiroclypeus carpaticus specimens in Gökçetepe possess more primitive features than those in Karaburun as recorded in the number of operculinid chambers (parameter X), further supporting the age relations of both sections. The occurrence of D. samantai, N. daguini, A. alticostata, and O. zitteli in association with H. gracilis and S. carpaticus in the latest Priabonian is reported here for the first time. Our findings prompt the revision of the upper stratigraphic ranges of these taxa in the Tethys.

Late Campanian to early Maastrichtian planktonic foraminiferal assemblages from Cretaceous oceanic red beds (CORBs) in the Yongla section, Gyangze, southern Tibet

Well-preserved and abundant planktonic foraminifera have been recovered from limestones of the Cretaceous oceanic red beds (CORBs) from the Yongla section in Gyangze, southern Tibet. This foraminiferal assemblage is dominated by species of Contusotruncana, Globotruncana, and Globotruncanita. The assemblage contains 21 species belonging to 7 genera and suggests a late Campanian to early Maastrichtian age, which permits amore precise age constraint for CORBs in the Gyangze area. This planktonic assemblage provides an important biostratigraphic datum for the correlations of theCORBs in theHimalayan region of the northern Tethys. The interval yielding foraminifers in the Yongla section may be the youngest known CORB in the Gyangze area.

Biozonation, Paleobathymetry and paleoenvironmental study of the Gurpi Formation in southwestern Iran

Planktonic foraminifera and major palynomorph groups (i.e. terrestrial, marine, and amorphous organic matter) of the Campanian-Selandian strata of the Gurpi Formation were studied to evaluate the changes in the Zagros paleobasin in southwestern Iran. Planktonic foraminifera were categorized into four morphotypes according to their paleodepth, extending from Morphotype 1, comprising surface generalists, to Morphotype 4, comprising deep-water aphotic heterotrophic species. The relative amount of species belonging to Morphotype 4 is noticeable in the Campanian-Maastrichtian. It shows that the depth of the basin was generally greater than 200 m in the Late Cretaceous. Two major sea-level regressional phases could be recognized during the formation deposition. The first one occurred near the middle of the Maastrichtian in the Contusotruncana contusa Biozone, during which the relative abundance of terrestrial palynomorphs increased prominently, and the species belonging to Morphotype 4 became notably rare. This regression correlates well with the eustatic curves, suggesting that it was controlled by global factors. Also, the species belonging to Morphotype 4 disappeared in the Danian, the relative abundance of terrestrial palynomorphs increased, and the relative abundance of planktonic foraminifera (P%) decreased prominently. However, this regression does not correlate with the eustatic curves and indicates that local tectonic events should be considered. The palynofacies study of the strata shows that during the Campanian-Maastrichtian, the strata were deposited in a deep suboxic-anoxic setting (Palynofacies IX), whereas the Danian strata were deposited in a shallow-shelf setting (Palynofacies VI). The studies show that during the Selandian, the depth of the basin increased again.

Paleoclimate of Upper Oligocene-Lower Miocene Temburong Formation, Klias Peninsula, Sabah, Base on Planktonic Foraminifera Assemblage

Planktonic foraminifera assemblages were studied for biostratigraphy and paleoclimatic interpretation of the Upper Oligocene-Lower Miocene of Temburong Formation, Klias Peninsula, Sabah. The Temburong Formation is composed of mainly flysh-type argillaceous deposit intercalations of slightly calcareous pelagic shale. Recently we discovered abundance of moderate to well-preserved planktonic foraminifera at the measured section and its planktonic assemblages are useful for biostratigraphy and paleoclimatic studies of Temburong Formation. A total of nine samples of shale were collected from three outcrops and processed based on standard micropaleontology method. Twenty-eight species of planktonic foraminifera were identified and grouped into three zones, namely: P21-P22 Globorotalia opima opima-Globigerina angulisuturalis zone, N4 Globigerinoides primordius-Globigerinoides quadrilobatus zone, and N5-N6 Catapsydrax dissimilis-Globigerinoides altiapetura zone. For paleoclimate studies, the relative abundance of planktonic foraminifera was obtained and grouped into climatic indices namely cool, cool-temperate, warm, warm-temperate and none climatic diagnostic. The result shows the changes of planktonic foraminifera assemblages and the paleoclimatic indices through Oligocene-Miocene boundary. The cool climate indices were identified at the lower part of the study section of Upper Oligocene sediment and gradually shifted to warm climatic indices at Lower Miocene section.