Planktonic Foraminifers Research Articles

The Yorktown Formation: Improved Stratigraphy, Chronology, and Paleoclimate Interpretations from the U.S. Mid-Atlantic Coastal Plain

The Yorktown Formation records paleoclimate conditions along the mid-Atlantic Coastal Plain during the mid-Piacenzian Warm Period (3.264 to 3.025 Ma), a climate interval of the Pliocene in some ways analogous to near future climate projections. To gain insight into potential near future changes, we investigated Yorktown Formation outcrops and cores in southeastern Virginia, refining the stratigraphic framework. We analyzed 485 samples for alkenone-based sea surface temperature (SST) and productivity estimates from the Holland and Dory cores, an outcrop at Morgarts Beach, Virginia, and the lectostratotype of the Yorktown Formation at Rushmere, Virginia, and analyzed planktonic foraminferal assemblage data from the type section. Using the structure of the SST record, we improved the chronology of the Yorktown Formation by establishing the maximum age ranges of the Rushmere (3.3–3.2 Ma) and Morgarts Beach (3.2–3.15 Ma) Members. SST values for these members average ~26 °C, corroborating existing sclerochronological data. Increasing planktonic foraminifer abundance, productivity, and species diversity parallel increasing SST over the MIS M2/M1 transition. These records constitute the greatest temporal concentration of paleoecological estimates within the Yorktown Formation, aiding our understanding of western North Atlantic temperature patterns, seasonality and ocean circulation during this interval. We provide a chronologic framework for future studies analyzing ecological responses to profound climate change.

An Oligocene olistostrome with exotic clasts in the Silesian Nappe (Outer Ukrainian Carpathians, Uzh River Basin)

In the Ukrainian part of the Silesian Nappe (Outer Carpathians, Uzh River Basin) the exotic clast-bearing Uzhok Olistostrome (up to 60 m thick) occurs within the Oligocene Krosno Formation and underlies the Pikui Sandstone (Otryt Sandstone in Poland). The Uzhok Olistostrome consists of debris/grain/mud flow deposits with clasts of schist and bioclastic limestone. These deposits contain redeposited pelagic sediments with planktonic foraminifers including Parogloborotalia pseudocontinuosa (Jenkins), Ciperoella ciperoensis (Bolli), Globoturborotalita woodi (Jenkins), Chiloguembelina adriatica Premec Fucek, Hernitz Kucenjak and Huber. The age of the Uzhok Olistostrome based on planktonic foraminifers correlates with the middle Oligocene within the middle O2–O5 zones. The source area for the Uzhok Olistostrome and Pikui Sandstone was a mid-Oligocene intrabasinal palaeouplift (the Pikui Ridge) interpreted as the fore-bulge located in the Silesian Sub-basin ahead the emerging Outer Carpathian accretionary prism (including the Dukla Nappe and other West Carpathian inner flysch nappes).

The response of calcareous plankton to the Sapropel S1 interval in North Ionian Sea

A high resolution study of calcareous nannofossils has been performed on samples from the Sapropel S1interval deposited in the North Ionian Sea, with the aim to assess the paleoenvironmental changes in the photic zone during this crucial interval in Mediterranean circulation. Calcareous nannofossil data have been integrated with planktonic foraminiferal data recently published from which the paleoclimatic curve has been constructed. Placoliths (namely Emiliania huxleyi) and Florisphaera profunda distributions, along with that of planktonic foraminifer Globigerinoides ruber white, evidence that, after a progressive weakening of surface water mixing, a deep chlorophyll maximum developed just prior to the sapropel deposition. We suggest that these changes took place as a response to enhanced precipitation conditions and riverine discharge as testified by increasing trend of reworked coccoliths and the occurrence of lower salinity taxon Braarudosphaera bigelowii. Calcareous nannofossils also point out that the oceanographic (water column stratification, reduced bottom water ventilation) and biogeochemical (increased primary production) processes that occurred during the S1 formation were particularly dominant during the earliest part of the older S1 warm phase (S1a). Our results support than some re-ventilation events of the shallow depth of studied site (665 m) occurred to some extent, particularly during the final phases of S1a. The distribution of holococcoliths, more abundant during the cold interruption phase S1i, seems confirm that the preservation of these tiny and delicate coccoliths, highly susceptible to dissolution, is enhanced under seafloor re-ventilation conditions. Finally, we tentatively suggest that preservation also plays a significant role in the distribution of the warm upper photic zone taxa, particularly during the warm S1b interval.

The K-Pg boundary section at Nasiłów, Poland: stratigraphic reassessment based on foraminifers, dinoflagellate cysts and palaeomagnetism

The Nasiłów section represents the uppermost part of the Middle Vistula River section, a classical Polish extra-Carpathian Cretaceous section, and gives access to the Cretaceous–Paleogene (K-Pg) boundary interval. Despite many papers that have been published so far, our newly collected data shed new light on the completeness of biostratigraphic and sedimentary records of the K-Pg at that site. The Nasiłów section encompasses the upper Maastrichtian regional XII and XIII foraminiferal assemblage zones and the lower Danian P0?-Pα standard planktonic foraminiferal zones. The K-Pg boundary is placed at the top of a phosphatic layer. The grey marly chalk unit, never before subjected to examination of biostratigraphically important taxa, displays blooms of guembelitrids pointing to the uppermost Maastrichtian (XIII foraminiferal assemblage Zone) as well as of planktonic and benthic foraminifers of a reduced test size. Such foraminiferal dwarfism is commonly observed near the end of the Cretaceous and interpreted as a response to the Deccan volcanism (possible 2nd phase) that caused climate changes and ocean acidification. The terminal Maastrichtian age of the marly chalk unit is additionally supported by an acme of the dinoflagellate cyst Palinodinium grallator , together with Tallasiphora pelagica and Disphaerogena carposphaeropsis . The “Greensand”, a distinct glauconite-quartz sand unit, contains exclusively terminal Maastrichtian planktonic foraminifers and dinoflagellate cyst assemblages. Individual specimens of Danian age are interpreted to be either an effect of contamination or were translocated down by burrowers into the Greensand. The lowermost portion of the Siwak (informal lithostratigraphic unit) demonstrates an early Danian age based on the co-occurrence of the common planktonic foraminifers Globoconusa daubjergensis, Guembelitria cretacea, Muricohedbergella monmouthensis, M. planispira, Planoheterohelix globulosa, Parvularuglobigerina extensa and P. alabamensis . The last occurrence of Palynodinium grallator and the first occurrences of Carptella cornuta and Senoniasphaera inornata , recorded directly above the phosphatic layer, support the same age assignment. The new palaeomagnetic data cannot prove remagnetization at the boundary interval, in contrast to previous research which gave support to a hiatus in the critical interval

Larger benthic and planktonic biostratigraphy and facies of Albian sediments in Coastal Fars Zone (Zagros area, south‐west Iran)

A total of 64 samples were collected from the Kazhdumi Formation (Albian) of south Zagros Basin (Coastal Fars Zone) in order to study the biostratigraphy and analyse the lithofacies. Stratigraphic distribution of identified larger benthic and planktonic foraminifers has confirmed the presence of three successive biozones: Mesorbitolina subconcava‐Orbitolina discoidea Zone, Favusella washitensis Zone followed by an upper Conicorbitolina conica‐Mesorbitolina parva Zone. Generally, orbitolinids are well developed in the Albian succession in the studied section, whereas the stratigraphic distribution of planktonic foraminifers is more restricted, dominating the Favusella washitensis Zone. Nevertheless, microscopic investigation recognizes five microfacies consisting of extraclast‐foraminifer packstone, peloid‐intraclast Orbitolina wackestone, foraminiferal plankton wackestone, intraclast‐Orbitolina grainstone, and coral‐rudist wackestone, which indicated a shallow water carbonates palaeoenvironment (intertidal, lagoon, bar) and open marine. The alternation of both planktic and benthic foraminifera through the Kazhdumi Formation confirms a rapid transgression and regression in the studied section during Albian time, which is attributed to Kazerun basement fault behaviour in the mentioned time interval.

Biogenic carbonate fluxes and preservation in the northwestern Labrador Sea since the Last Glacial Maximum

The important changes that took place in the glacial cycle at the termination, from the Last Glacial Maximum to the present interglacial, deserve an examination of ocean sedimentary records that document past productivity, carbon fluxes, and carbonate preservation. In this study, we analyzed coccoliths, alkenones, and foraminifers in core HU2008–029-004 PC (61.46°N and 58.04°W, water depth = 2,674 m) from the northwestern Labrador Sea to document linkages between hydrographic conditions, biogenic carbonate fluxes to the seafloor, and their preservation/dissolution during the last 25,000 years. Large changes in coccolith and foraminifer concentrations are recorded, with sediments from the last glacial interval containing significantly less carbonate microfossils (9.5 ± 3.9 × 105 coccoliths g−1 and 2,860 ± 580 planktonic foraminifers g−1) than sediments from the deglacial and postglacial intervals (up to 3.1 × 108 coccoliths g−1 and 2.9 × 104 foraminifers g−1). Three foraminifer-based calcite dissolution indices were used to evaluate biogenic carbonate preservation: the planktonic foraminifer fragmentation index, the ratio of benthic-to-planktonic foraminifers (B/P), and the ratio of organic linings to benthic foraminifers (OL/B). Fragmentation remained low throughout the postglacial (mean of 4%) but reached up to 8% in the deglacial and peaked at 16% in samples from the Bølling-Allerød of the late glacial interval. Samples from the Bølling-Allerød and the deglacial interval also display a slightly elevated B/P index (>0.15), which suggests that some dissolution may have occurred. In contrast, with the exception of the Bølling-Allerød and the deglacial interval, near zero OL/B values characterize most of the sequence, suggesting good biogenic carbonate preservation, which implies that the low biogenic carbonate and coccolith content in sediments of the glacial stage mirror low productivity of calcifying organisms. The elevated fragmentation of foraminifers during the Bølling-Allerød and the deglacial interval, a time of elevated productivity and low percentages of ice-rafted debris, may indicate the development of calcite undersaturated porewaters and consequent dissolution resulting from oxic remineralization of sedimentary organic matter. We also identify a significant decoupling of coccolith and alkenone concentrations throughout the core. Colder-than-expected UK37-SST estimates from the alkenones of the glacial interval rule out possible allochthonous inputs from lower-latitude locations. Instead, our records imply that at least during the glacial interval, alkenones were produced by non-calcifying haptophytes that may not follow the canonical UK37-based temperature calibrations.

The Dynamics of Diachronous Extinction Associated With Climatic Deterioration Near the Neogene/Quaternary Boundary

AbstractTo predict extinction, we must understand the processes leading to terminal population decline. Once a critical threshold of population size is reached, small environmental perturbations can push a species over the cliff‐edge to extinction, so the main drivers of extinction are the factors that cause the initial reduction in population size. Most studies of population decline leading up to extinction focus on modern species in a human‐dominated world. The drivers of population decline leading to non‐human mediated extinctions are less well known but changes in climate are arguably the most widely invoked mechanism. Here, we report data on >16,000 individuals of the planktonic foraminifer Globoconella puncticulata from six sites in the Atlantic Ocean along an 83 degree‐long latitudinal transect, over a 600,000‐years interval leading up to the species’ global extinction during the late Pliocene‐earliest Pleistocene intensification of Northern Hemisphere glaciation. We show changes in geographic range, abundance, and body size. We find that populations do not follow a North‐to‐South sequence in extinction as Earth cooled and developed large ice sheets in the high latitudes of the Northern Hemisphere. Instead, our results suggest that (a) populations are differentially adapted to local environmental conditions such as nutrient availability, (b) population dynamics in core populations differ from those at the edge of their range, and (c) individual population responses to external pressures are essential to understanding the drivers of global extinction. Our study demonstrates the potential to transform our understanding of extinction dynamics through spatially replicated sampling of the highly resolved marine microfossil record.

Upper Campanian-lower Maastrichtian integrated carbon isotope stratigraphy and calcareous microplankton biostratigraphy of North-central Tunisia

A comprehensive stratigraphic framework is presented for the upper Campanian-lower Maastrichtian succession of the Elles section in North-central Tunisia. This has been done by applying an integrated approach including calcareous nannofossil and planktonic foraminiferal biostratigraphy in conjunction with carbon isotope stratigraphy. The studied interval spans from the Uniplanarius sissinghii (CC21) to Reinhardtites levis (CC24) calcareous nannofossil zones and their coeval planktonic foraminiferal zones from the Contusotruncana plummerae Zone to Planoglobulina acervulinoides Zone. Seven positive and negative δ13C events have been recognized and considered for high-resolution global correlation. Isochroneity and diachroneity of the microplankton bioevents regarding the carbon isotope stratigraphy were assessed. Some discrepancies were reported, and some of them denote actual diachronism. However, the impact of the different taxonomic concepts and/or environmental issues cannot be totally excluded. The Campanian/Maastrichtian boundary has been precisely positioned within the lowermost part of the El Haria Formation at the base of the δ13C event CMBc (72.15 ± 0.05 Ma). This level projects directly below the first occurrence of the planktonic foraminifer Gublerina cuvillieri and about 9.4 m below the last occurrence of the nannofossil Uniplanarius trifidus.

Latitudinal Differentiation among Modern Planktonic Foraminiferal Populations of Central Mediterranean: Species–Specific Distribution Patterns and Size Variability

Studies of the spatial distribution and size of modern planktonic foraminifera are still lacking in the Mediterranean Sea. In this study, 17 core-top sediments collected from a north-south transect along the central Mediterranean have been analyzed for planktonic foraminiferal content, in terms of their distributional pattern and intraspecific size variability. Among the analyzed planktonic foraminiferal species, Globigerina bulloides and Globigerinoides ruber (w) were the most abundant, presenting an antagonistic behavior and an overall decreasing trend in their average size values from Adriatic to Ionian sub-basins. Intraspecific differences have been also documented for G. ruber (w), with the dominant sensu stricto morphotype to present generally higher frequencies and more constant shell sizes than sensu lato. The greater size variability of the latter is possibly related to its adaptation in particular hydrographic conditions based on its depth habitat preference and ecological characteristics to reach the (sub)optimum growth conditions. The rest of the species occur in minor percentages and show on average 11% increase with decreasing latitude characterized by distinct species-specific size variations along the transect. Our results show that the relationship between planktonic foraminifera shell size and abundance or sea surface temperature are either absent or weaker than previously reported for other regions and that in central Mediterranean assemblages’ size may be mainly related to nutrient availability. Besides the environmental parameters (sea surface temperature, primary productivity, water depth, stratification), the possible hidden cryptic diversity, still lingers to be consistently determined, could give a better understanding of the geographic and morphological differentiation within the Mediterranean planktonic populations.

Disruption of the Atlantic Meridional Circulation during Deglacial Climates Inferred from Planktonic Foraminiferal Shell Weights

Changes in the density structure of the upper oceanic water masses are an important forcing of changes in the Atlantic Meridional Overturning Circulation (AMOC), which is believed to widely affect Earth’s climate. However, very little is known about past changes in the density structure of the Atlantic Ocean, despite being extensively studied. The physical controls on planktonic foraminifera calcification are explored here, to obtain a first-order approximation of the horizontal density gradient in the eastern Atlantic during the last 200,000 years. Published records of Globigerina bulloides shells from the North and Tropical eastern Atlantic were complemented by the analysis of a South Atlantic core. The masses of the same species shells from three different dissolution assessed sediment cores along the eastern Atlantic Ocean were converted to seawater density values using a calibration equation. Foraminifera, as planktonic organisms, are subject to the physical properties of the seawater and thus their shells are sensitive to buoyancy forcing through surface temperature and salinity perturbations. By using planktonic foraminifera shell weight as an upper ocean density proxy, two intervals of convergence of the shell masses are identified during cold intervals of the last two deglaciations that may be interpreted as weak ocean density gradients, indicating nearly or completely eliminated meridional circulation, while interhemispheric Atlantic density differences appear to alleviate with the onset of the last interglacial. The results confirm the significance of variations in the density of Atlantic surface waters for meridional circulation changes.

Coiling directions in the planktonic foraminifer Pulleniatina: A complex eco-evolutionary dynamic spanning millions of years.

Planktonic foraminifera are heterotrophic sexually reproducing marine protists with an exceptionally complete fossil record that provides unique insights into long-term patterns and processes of evolution. Populations often exhibit strong biases towards either right (dextral) or left (sinistral) shells. Deep-sea sediment cores spanning millions of years reveal that some species show large and often rapid fluctuations in their dominant coiling direction through time. This is useful for biostratigraphic correlation but further work is required to understand the population dynamical processes that drive these fluctuations. Here we address the case of coiling fluctuations in the planktonic foraminifer genus Pulleniatina based on new high-resolution counts from two recently recovered sediment cores from either side of the Indonesian through-flow in the tropical west Pacific and Indian Oceans (International Ocean Discovery Program Sites U1486 and U1483). We use single-specimen stable isotope analyses to show that dextral and sinistral shells from the same sediment samples can show significant differences in both carbon and oxygen isotopes, implying a degree of ecological separation between populations. In one case we detect a significant difference in size between dextral and sinistral specimens. We suggest that major fluctuations in coiling ratio are caused by cryptic populations replacing one another in competitive sweeps, a mode of evolution that is more often associated with asexual organisms than with the classical ‘biological species concept’.

Enhanced Carbonate Dissolution Associated With Deglacial Dysoxic Events in the Subpolar North Pacific

AbstractHere we use volume density (ρV) measurements as a metric of size‐normalized weights for Neogloboquadrina pachyderma, a planktonic foraminifer, from upper OMZ and abyssal depth sites in the Gulf of Alaska over the past ∼20,000 years to test for covariation between carbonate preservation and OMZ intensity. We find that dissolution of N. pachyderma is most intense at the upper OMZ site where oxygenation is generally lower than at the abyssal site. We also examine Uvigerina peregrina, a benthic foraminifer, at the upper OMZ site and find that the lowest ρV measurements in both taxa occur during deglacial and early Holocene dysoxic events. We use computed tomography images to confirm that changes in ρV are related to shell thickness, observe dissolution features, and test for growth influences on ρV. Further, we use stepwise selection of multiple regression models in which coregistered environmental proxies are potential predictors of ρV and find that the best supported models retain negative associations between ρV and the concentration of redox‐sensitive metals and the relative abundance of dysoxia‐tolerant and opportunistic benthic foraminifera, indicating that low ρV is associated with low‐oxygen conditions and pulsed availability of organic matter at the seafloor. Taken together, our results suggest the primary driver of carbonate dissolution here is related to organic carbon respiration at the seafloor. This highlights the importance of metabolic dissolution in understanding the inorganic carbon cycle and the role regions with high‐organic carbon export, such as OMZs, can have as CO2 sources as metabolic dissolution intensifies.

Atmospheric carbon dioxide variations across the middle Miocene climate transition

Abstract. The middle Miocene climate transition ∼ 14 Ma marks a fundamental step towards the current “ice-house” climate, with a ∼ 1 ‰ δ18O increase and a ∼ 1 ‰ transient δ13C rise in the deep ocean, indicating rapid expansion of the East Antarctic Ice Sheet associated with a change in the operation of the global carbon cycle. The variation of atmospheric CO2 across the carbon-cycle perturbation has been intensely debated as proxy records of pCO2 for this time interval are sparse and partly contradictory. Using boron isotopes (δ11B) in planktonic foraminifers from Ocean Drilling Program (ODP) Site 1092 in the South Atlantic, we show that long-term pCO2 varied at 402 kyr periodicity between ∼ 14.3 and 13.2 Ma and follows the global δ13C variation remarkably well. This suggests a close link to precessional insolation forcing modulated by eccentricity, which governs the monsoon and hence weathering intensity, with enhanced weathering and decreasing pCO2 at high eccentricity and vice versa. The ∼ 50 kyr lag of δ13C and pCO2 behind eccentricity in our records may be related to the slow response of weathering to orbital forcing. A pCO2 drop of ∼ 200 µatm before 13.9 Ma may have facilitated the inception of ice-sheet expansion on Antarctica, which accentuated monsoon-driven carbon cycle changes through a major sea-level fall, invigorated deep-water ventilation, and shelf-to-basin shift of carbonate burial. The temporary rise in pCO2 following Antarctic glaciation would have acted as a negative feedback on the progressing glaciation and helped to stabilize the climate system on its way to the late Cenozoic ice-house world.

Integrated biochronology of the pliocene deposits of the Estepona basin (Málaga, S Spain). Palaeobiogeographic and palaeoceanographic implications

In the Estepona basin (Málaga, S Spain), the richest and the most diverse Pliocene sites of marine invertebrates (mostly molluscs) of the Mediterranean are found. Most of the species described up until now (~95% out of 892 identified species) occur at the Parque Antena and the Velerín Area (Velerín, Velerín-Carretera and Velerín-Antena) sites. Although molluscs are very well known, the age of these important sites is still controversial. In this paper, a biochronological study of these sites based on an integrated study of the microfossil (calcareous nannoplankton and planktonic foraminifers) and macrofossil (molluscs) assemblages is presented. The Parque Antena and Velerín-Carretera sites can be attributed to the late Zanclean (uppermost part of the early Pliocene) based on the presence of Globorotalia margaritae, Gr. puncticulata and Gr. group crassaformis (including Gr. crassaformis s.s.). Nannoplankton assemblages agree with this age, and can be attributed to the CN11b biozone of Okada & Bukry (1980) due to the presence of small Gephyrocapsa, Sphenolithus abies and Reticulofenestra pseudoumbilica. At the Velerín-Antena section, the bioindicators of the early Pliocene Gr. margaritae, Sphenolithus abies and Reticulofenestra pseudoumbilica are absent. The molluscs found in the studied sites correlate with the Mediterranean Pliocene Molluscan Unit 1 of Raffi & Monegatti (1993) (MPMU1). Finally, the coexistence of Gr. margaritae and Gr. group crassaformis in the Mediterranean domain is described for the first time.

The Adıyaman Group carbonate succession on the northern Arabian Plate (southeastern Turkey): A review of lithostratigraphy, foraminiferal biostratigraphy, depositional environments and sequence stratigraphic evolution

Abstract This study presents a new stratigraphic framework for the Adiyaman Group succession developed on the northern margin of the Arabian Platform. This Upper Cretaceous carbonate sequence, distributed widely in outcrop and subsurface rocks in the southeast Anatolia region, is investigated in terms of lithostratigraphy, biostratigraphy, microfacies analysis and sequence stratigraphy. The sequence is divided into six lithostratigraphic units, which in ascending order are the Karabogaz, Saytepe, Saydere, Sayindere, Beloka and Sanli formations. Based on examination of benthic and planktonic foraminifera, the Adiyaman Group ranges in age from late Santonian to early late Campanian. The Saytepe, Beloka and Sanli formations are characterized by benthic foraminifers, while the Karabogaz, Saydere and Sayindere formations are defined by planktonic foraminifers. Following a detailed microfacies analysis, the Adiyaman Group carbonates are interpreted to have been deposited in settings that range from deep shelf to lagoonal depositional environments. Sequence stratigraphic studies identified three successive third-order depositional sequences that are separated by sequence stratigraphic surfaces. Sequence boundaries are correlated to global cycle boundaries. The abundance and diversity of foraminifera are interpreted as a function of relative sea-level changes. This study provides revisions in stratigraphic nomenclature that rely on precise biostratigraphic data.

Messinian West Alboran Sea record in the proximity of Gibraltar: Early signs of Atlantic-Mediterranean gateway restriction

Late Miocene sedimentary records in the Gibraltar arch region hold fundamental information on the Atlantic-Mediterranean connectivity before, during and after the Messinian Salinity Crisis (MSC; 5.96-5.33 Ma). In this work we tackle this still unresolved problem through a detailed foraminifer-based biostratigraphy, micropaleontological and geochemical analyses of four available records (ODP 976B and DSDP 121) and boreholes (Andalucia-G1 and Alboran A1) in the West Alboran Basin (WAB). The combined use of these different analytical techniques together with new seismic stratigraphy enabled us to create a new and revised Upper Tortonian-Lower Pliocene Alboran Sea chronostratigraphic framework and estimate the magnitude of the Zanclean erosion. At Site 976, the dominance of a peculiar cold planktonic foraminifer fauna in the late Tortonian-early Messinian could possibly imply the existence of a proto-Gibraltar Strait, while at ~7.2 Ma, changes towards warmer foraminifer assemblages, increasingly stratified water column and sharp increase in terrestrial input indicate the beginning of the restriction of the Mediterranean from the Atlantic Ocean. Cyclical changes visible both in the elemental composition and foraminifer assemblages from here onward highlight a strong precessional cyclicity, which can be correlated to the first signs of reduced ventilation and sapropel deposition in the Eastern Mediterranean. The integration of seismic profiles and core analyses finally revealed that the Messinian expression in the Alboran basin is limited to two units: one hemipelagic and one chaotic, most probably connected to the MSC final stages. The Messinian succession in the Alboran basin is topped by an unconformity, most likely related with the Zanclean reflooding, which eroded a sedimentary succession of ~1.67 Ma. An extremely rare phosphate (canaphite) and Mg rich minerals were recognized described and associated to interstitial fluids and diagenetic processes.

Reconstruction of oceanographic and environmental conditions in the eastern Mediterranean (Kottafi Hill section, Cyprus Island) during the middle Miocene Climate Transition

The multi-proxy investigation of the deep-marine Kottafi Hill section (KHS), a part of the carbonate system of the Miocene Pakhna Formation, Cyprus, involved such proxies as calcareous nannofossil analysis, measurements of the oxygen and carbon isotope composition of the planktonic foraminifer Orbulina universa, and determination of the pollen and palynomorph contents, revealed the importance of these sedimentary sequences in the assessment of the impact of major global events during the middle Miocene on the regional scale. The KHS spans the 20.89–11.6 Ma time interval, during which eighteen OC-rich siltstone intercalated laminae have been deposited under warm and humid climate at 15.5–11.6 Ma. These layers can be possibly considered as the precursors of sapropelic layers mostly developed in the eastern Mediterranean Basin during Pliocene–Holocene. The global glacial events Mi3a–Mi5, traced by δ18O planktonic foraminifera records in the KHS, represent the stepwise cooling phase during the middle Miocene Climate Transition.

Testing the stratigraphic consistency of Pleistocene microfossil bioevents identified on the Alpha and Lomonosov Ridges, Arctic Ocean

ABSTRACT Two different biostratigraphic approaches are used to identify Marine Isotope Stage 11 (MIS 11) in Arctic Ocean sediments. On the Lomonosov Ridge, globally calibrated nannofossil bioevents constrain the age of sediments back to MIS 13 (Core LOMROG12-3PC). In the Amerasian Basin the unique occurrence of the planktonic foraminifer Turborotalita egelida is increasingly used as a marker for MIS 11. However, the T. egelida horizon has only been dated using cyclostratigraphy. Here we bridge these approaches through investigation of a new core (AO16-8GC) from the Alpha Ridge, Amerasian Basin. AO16-8GC is easily correlated to LOMROG12-3PC and contains the T. egelida horizon, allowing the first comparison between the biostratigraphy of both regions. Based on the nannofossil biochronology of LOMROG12-3PC, the most convincing lithologic correlation between the Alpha and Lomonosov Ridge cores places the T. egelida horizon between MIS 15 and MIS 17. This potentially older age for the T. egelida biohorizon emphasizes the need for continued caution in interpreting paleoceanographic records predating MIS 6, until further work can reconcile the nanno- and microfossil biostratigraphies that are emerging for middle Pleistocene sediments of the central Arctic Ocean.

Planktonic Foraminiferal Biosatratigraphy of the Eocene – Oligocene Boundary at Sinjar Area, NW Iraq

The present study deals with the lithostratigraphy, biostratigraphy and chronostratigraphy of the Eocene- Oligocene boundary in three surface sections in Sinjar anticline, northwestern Iraq. Jaddala Formation composed of marl, marly limestone represents deep Eocene facies, Palani, and Tarjil formations represent Early and Late Oligocene sequences. Sixty-two planktonic foraminiferal species belonging to sixteen genera have been recognized which permit the recognition of four Zones; these are from older at the base: Globorotalia opima opima Total- Range Zone (P21) Globigerina ampliapertura partial- Range Zone (P20) Pseudohastigerina micra Interval Zone (P 19) Globigerinatheka subconglobata subconglobata Partial Range Zone (P11) (Part). The Eocene- Oligocene boundary in Sinjar area represents disconformity surface, where the deposition ceased in the Middle Eocene (Lutetian) at the end of Jaddala Formation, then deposition started at the Upper Early Oligocene due to rapid wide transgression, leading to the deposition of Palani (Rupelian) and Tarjil (Chatian) formations, which consist of thinly laminated hard white-pale brown intercalation of marly limestone and marl beds.

The Monterey Event in the Mediterranean platform to basin transition: The Guadagnolo Formation (Miocene, Prenestini Mountains, Central Apennines)

The stratigraphic evolution of the Guadagnolo Fm, developed on the transition between the Latium-Abruzzi Platform and the Umbria Sabina Basin (central Apennines), was studied through facies and stable isotope analysis. Calcareous nannofossil biostratigraphy allows to identify the Burdigalian-Langhian boundary, constraining the sections to the lower to middle Miocene. This interval consists of marly deposits forming the intermediate member of the formation dominated by sponge spicules, molluscs, bryozoans, benthic and planktonic foraminifers. This member is deposited in a distal outer ramp where the abundance of siliceous sponges has been attributed to the high seawater fertility coinciding with the Monterey event, enhanced by regional nutrient flux due to continental runoff and volcanism. The upper member is Serravallian and consists of bryozoan-dominated cross-bedded calcarenites deposited in a shallower environment of the outer ramp.A positive carbon isotope excursion was correlated with the Monterey event recorded in the Central Apennines carbonate ramps and from ODP sites. Five carbon maxima belonging to the Monterey Carbon Isotope Excursion have been identified. Four carbon isotope peaks fall in the spongolitic member, one in the upper member. The Carbon Maxima recorded within the spongolitic member show an attenuate isotope excursion compared with the pelagic and the carbonate platforms record. The weaker signal is due to the fractionation effect of primary producers of the photic zone and to the sponge release of 12C-enriched CO2 deriving from the oxidation of organic matter. Conversely, the largest positive carbon isotope excursion is recorded in the upper member, representative of a shallower environment, and it is due to the absence of sponges and the increased contribution of photosynthetic biota. The shoaling of the depositional environment is related to the global cooling recorded after 14 Ma, as evident also from the δ18O positive shift at the base of the upper member of the Guadagnolo Fm.