Lutetian calcareous nannofossil events in the Agost section (Spain): implications toward a revision of the Middle Eocene biomagnetostratigraphy

This paper presents a detailed calcareous nannofossil biostratigraphy of the entire Lutetian of the Agost section (Betic Cordillera, SE Spain). This investigation integrates and improves on previous study performed through the Ypresian/Lutetian boundary by the authors on this succession. The new revision of the integrated bio‐magnetobiochronology of the Early/Middle Eocene interval revealed highly diversified calcareous nannofossil assemblages, characterizing more than 8 Myr of climatic variability. The studied interval spans from Zone CP11 to Subzone CP14a and from the upper part of Zone NP13 to the base of Zone NP16 of calcareous nannofossil standard zonations. The revision of the calcareous nannofossil content enabled the identification of numerous secondary events which greatly improved the stratigraphic resolution of this time interval. An important re‐organization of the nannoflora was observed during the Y/L transition, when Reticulofenestra and Dictyococcites (Noelaerhabdaceae) became the most important genera in terms of abundance and dispersal, dominating the Middle Eocene nannofossil assemblages and replacing Toweius and Discoaster taxa characteristic of the lower Eocene. Pentaliths and Blackites experience a great expansion and diversification, whereas Discoaster and Chiasmolithus which are well diversified but never abundant during the Lutetian show a slow turnover. A reassessment of the major bio‐events observed in the Noelaerhabdaceae family as well as revision and correlation of these events with the classical Italian sections (Contessa and Bottaccione) are presented. The new results show that biostratigraphic problems related to the Middle Eocene chronology are not limited to the correlation between calcareous nannofossils and planktonic foraminiferans at the Y/L transition but extend to calcareous nannofossil events commonly used for correlating the Bartonian.     

Integrated quantitative biostratigraphy of the latest Tortonian-early Messinian Pissouri section (Cyprus): An evaluation of calcareous plankton bioevents

A quantitative study was performed on planktonic foraminifera and calcareous nannofossils of the astronomically dated Late Miocene Pissouri section (Cyprus). Our results confirm the reliability of well-known planktonic foraminiferal events as Catapsydraxparvulus LO (Last Occurrence), sinistral coiling change of Globorotaliascitula, Globorotaliamiotumida group FRO (First Regular Occurrence), Globorotalianicolae FO (First occurrence) and LO, sinistral coiling change of Neogloboquadrinaacostaensis and also of several important calcareous nannofossil events (Amaurolithusprimus FO, Amaurolithusdelicatus FO, Reticulofenestrarotaria FO and FCO). Integrated planktonic foraminifera and calcareous nannoplankton data contribute to an enhanced time resolution of the Tortonian - early Messinian interval in the Levantine basin, and contribute to detailed correlations throughout the Eastern Mediterranean. In addition, we compare methodologies commonly used in calcareous plankton biostratigraphy, and shortly outline sources of bias that can influence the results of stratigraphic studies.     

Refinements of calcareous nannofossil biostratigraphy at the Miocene/Pliocene Boundary in the Mediterranean region

The high-resolution quantitative study of the calcareous nannofossil assemblages in two Mediterranean deep-sea successions (ODP Sites 969B and 975B) encompassing the Miocene/Pliocene boundary allows the recognition of a set of reliable bioevents useful to detecting the base of the Zanclean stage. The results have been successfully compared with two on-land sections (Cava Serredi, Tuscany, and Montepetra borehole, Marche Region, Central Italy). This study confirms that Ceratolithus acutus and Triquetrorhabdulus rugosus, the markers traditionally used for identifying the Miocene/Pliocene Boundary are very rare in the Mediterranean area and cannot be used for biostratigraphic correlation. Conversely, the absence interval (paracme) of Reticulofenestra pseudoumbilicus and the distribution range of a new species belonging to the Reticulofenestra genus (Reticulofenestra zancleana nov. sp.) show high biostratigraphical potential. The position of the new biohorizons has been compared to those of the planktonic foraminifers events, and correlated to the CaCO₃ cycles reconstructed for the two sections. On the basis of these new nannofossil bioevents, Rio et al.’s (1990) MNN12 biozone is subdivided into three subzones, thus improving the biostratigraphic resolution of the Early Pliocene.     

Earliest Zanclean age for the Colombacci and uppermost Di Tetto formations of the “latest Messinian” northern Apennines: New palaeoenvironmental data from the Maccarone section (Marche Province, Italy)

The occurrence of planktonic foraminifers in the latest Messinian deposits (uppermost Di Tetto Formation and Colombacci Formation) of the Marche Province (Apennine foredeep, Italy) has stimulated a debate since the 1970s. An earlier palynological study of the entire Maccarone section revealed a pronounced, and a sudden increasing frequency of saccate pollen grains which indicates more distal conditions, and thus a transgression. At first attributed to tectonic activity, this transgression is now interpreted as representing the Zanclean marine transgression after the discovery of Ceratolithusacutus, the calcareous nannofossil marker of the earliest Zanclean in the Mediterranean Sea. Evidence from marine dinoflagellate cysts and planktonic foraminifers supports this result. The Colombacci Formation and uppermost part of the Di Tetto Formation (i.e. the entire p-ev2 stratigraphic unit) belong to the earliest Zanclean. The so-called Lago Mare no longer has a regional chronostratigraphic sense, and should be understood as the invasion of Paratethyan organisms via surface waters owing to a connection at high sea-level between the Aegean Sea and the Eastern Paratethys (Dacic Basin). A new robust environmental reconstruction of the northern Apennine foredeep is proposed, which respectively considers the effects of tectonics and Mediterranean eustasy.     

Biostratigraphic significance of sequential size variations of the calcareous nannofossil genus Reticulofenestra in the Upper Pliocene of the North Atlantic

We demonstrate size fluctuations of the calcareous nannofossil genus Reticulofenestra in Upper Pliocene sediments from the North Atlantic Ocean and clarify a characteristic evolutionary trend of this genus. Four bioevents, which are based on abrupt decreases in maximum size and on changes of morphologic features of Reticulofenestra specimens, are detected in the sediments. They are the disappearance of R. minutula var. A, the termination of Acme Zone II of R. minutula var. C, the disappearance of R. minutula var. B, and the termination of Acme Zone I of R. minutula var. C, in ascending order. These are nearly synchronous and traceable events.     

Response of calcareous nannofossils to the Paleocene–Eocene Thermal Maximum: Observations on composition,preservation and calcification in sediments from ODP Site 1263 (Walvis Ridge — SW Atlantic)

In this study we present the results of a detailed analysis on calcareous nannofossil assemblages from sediment cores of ODP Site 1263 (Southern East Atlantic, Walvis Ridge). This section represents one of the few complete deep-sea sections that document the Paleocene–Eocene Thermal Maximum (PETM) in the pelagic realm. The PETM transient event was characterized by a brief, but intense interval of global warming, a global negative carbon isotope excursion (CIE), and widespread dissolution of seafloor carbonate sediments. Paired analysis at polarizing light microscope (LM) and Scanning Electron Microscope (SEM) documents the different “behavior” of nannofossils through the different phases of the PETM, at the onset of CIE, within the CIE, and during the recovery interval. The presence of anomalous specimens and morphotypes within some nannofossil taxa, recorded during previous LM high resolution analyses, has been further investigated in selected samples at the SEM. Besides the known representatives of the CIE-PETM “excursion nanno-flora”, as Rhomboaster calcitrapa group and Discoaster anartios, the analysis revealed the presence of peculiar morphotypes of Fasciculithus and deformed specimens of Discoaster nobilis group, Discoaster mediosus and Discoaster multiradiatus that are considered related to the anomalous amount of CO₂ in the ocean-atmosphere system during the early phase of PETM. Comparative analyses were performed in few selected samples from other PETM sections located at different latitudes in the Atlantic and Pacific oceans. Although the anomalous geochemical conditions during the PETM-CIE interval seem to have had some influence on the nannofossil production, calcification and assemblage composition, it results that local productivity together with post depositional (diagenetic) conditions were additional important controlling factors on nannofossil assemblages. Preliminary data from Eocene Thermal Maximum 2 (ETM2 or Elmo) suggest that nannofossil malformations are not exclusive of the PETM, and are associated to other episodes of perturbation of the C cycle.     

Calcareous nannofossil biostratigraphy of the M. del Casino section (northern Apennines,Italy) and paleoceanographic conditions at times of Late Miocene sapropel formation

A detailed quantitative calcareous nannofossil analysis has been performed on 138 samples from the astronomically dated Monte del Casino section with the aim to identify and precisely date the most important calcareous nannofossil events across the Tortonian/Messinian boundary in the Mediterranean, and to unravel paleoceanographic conditions at times of sapropel formation during the Late Miocene. From the biostratigraphic perspective, the genus Amaurolithus provides three successive first occurrences (FOs): A. primus, A. cf. amplificus and A. delicatus, dated at 7.446, 7.434 and 7.226 Ma, respectively. Other bioevents include the base and top of the `small reticulofenestrids' Acme, dated at 7.644 and 6.697 Ma, and the FO, FCO and LO of R. rotaria, dated at 7.405, 7.226 and 6.771 Ma. These events appear to be useful in improving biostratigraphic resolution in the Tortonian–Messinian boundary interval, at least for the Mediterranean. Quantitative analysis revealed changes in the calcareous nannofossil assemblage associated with the sapropels. The observed fluctuations suggest a single mechanism for sapropel formation in the Mediterranean during the late Neogene. Sapropels are characterized by a decrease in the total number of coccoliths, interpreted mainly as a reduction in calcareous nannofossil production due to increased siliceous plankton production during spring blooms; and an increase in reworked specimens, interpreted to reflect enhanced continental input via river run-off. An increase in abundance of the genus Rhabdosphaera can be explained by opportunistic behavior at the end of the spring bloom when nutrient levels start to become impoverished. As far as sea surface water temperature indicators are concerned, warm water D. pentaradiatus shows positive fluctuations in sapropels while cooler water D. intercalaris and C. pelagicus show negative fluctuations.     

The response of calcareous nannofossil assemblages to the Paleocene Eocene Thermal Maximum at the Walvis Ridge in the South Atlantic

Compositions and abundances of calcareous nannofossil taxa have been determined in a ca 170 kyrs long time interval across the Paleocene/Eocene boundary at 1-cm to 10-cm resolution from two ODP Sites (1262, 1263) drilled along the flank of the Walvis Ridge in the South Atlantic. The results are compared to published data from ODP Site 690 in the Weddell Sea. The assemblages underwent rapid evolution over a 74 kyrs period, indicating stressed, unstable and/or extreme photic zone environments during the PETM hyperthermal. This rapid evolution, which created 5 distinct stratigraphic horizons, is consistent with the restricted brief occurrences of malformed and/or weakly calcified morphotypes. The production of these aberrant morphotypes is possibly caused by major global scale changes in carbon cycling in the ocean–atmosphere system, affecting also photic zone environments. No marked paleoecologically induced changes are observed in abundances of the genera Discoaster, Fasciculithus and Sphenolithus at the Walvis Ridge sites. Surprisingly, there is no significant correlation in abundance between these three genera, presumed to have had a similar paleoecological preference for warm and oligotrophic conditions.     

Preliminary study of the calcareous taphocoenoses in Late Quaternary glacial marine sequences of the Ross Sea (Antarctica)

Three gravity cores were collected in north-western Ross Sea (Coulman Island and Cape Adare areas) during 1998 and 1999 “Progetto Nazionale Ricerche in Antartide”. Several carbonate-rich levels, from Late Pleistocene to Holocene in age, interbedded with glacial marine sequences were recovered. Examination of the compositional characters (X-ray structure, texture, water, TOC and CaCO₃ contents) and taphonomic data (fabric of the fossil concentration, degree of preservation of foraminifers and bryozoans, together with paleoecological inferences) has allowed the preliminary documentation of oscillations of the ice-shelf front in this area. Benthic foraminifer tests in glacial marine sediments older than the Last Glacial Maximum are often badly preserved (abraded and broken), testifying to the persistent transport of these sediments. In the younger sediments, an increased concentration of Neogloboquadrina pachyderma occurs, indicating more open water conditions. The occurrence of a mainly autochthonous fauna in muddy sediments in between two volcanic events in the Coulman Island area could indicate stable environmental conditions. The occurrence of limited % of fragmented foraminifers indicates the decreasing influence of glacial reworking. In the Cape Adare area, mass flow events were common during the Holocene retreat of the ice shelf. Several bioclastic-rich deposits (stylasterids and bryozoans assemblage) in the studied core with interbedded muddy sediments could indicate mass transport events from neighboring shallow environments. During undisturbed open-marine conditions, represented by muddy sedimentation, foraminifers and other calcareous taxa colonized the previous coarse-textured skeletal substratum.     

Calcareous nannofossil biostratigraphy (Upper Bajocian-Lower Bathonian) of the Ravin du Bès section (Bas Auran, Subalpine Basin, SE France): Evolutionary trends of Watznaueria barnesiae and new findings of “Rucinolithus” morphotypes

A biostratigraphic study based on calcareous nannofossils was performed on the Ravin du Bès section (Bas Auran area, SE France). Semi-quantitative estimates of total nannofossil and single species abundances showed that calcareous nannofloras are rare to common and their preservation is poor to moderate. The following biohorizons were identified and calibrated to ammonite biozonation: the first occurrence (FO) of Watznaueria aff. W. communis, the FO of Pseudoconus enigma; the FO of “Rucinolithus”; the last occurrence (LO) of Carinolithus magharensis; the FO of Stephanolithion speciosum octum and the FO of Watznaueria barnesiae. These results confirm that calcareous nannofossils are good biostratigraphic markers for the Bajocian/Bathonian boundary interval. Moreover, the occurrence of P. enigma allows a direct calibration between Tethyan and Boreal nannofossil events and biozones. Morphometric analyses were performed on the W. communis-W. barnesiae group in order to quantify changes between the two taxa. The intermediate form W. aff. W. communis has been identified; it comprises coccoliths very similar to W. communis, but with central area length ≤ 0.9 μm. This study allowed the detailed reconstruction of the evolutionary trends from W. communis to W. barnesiae: the intermediate taxon W. aff. W. communis appears abruptly in the latest Bajocian and persists after the FO of W. barnesiae in the earliest Bathonian. Our results support the model of punctuated equilibrium rather than a phyletic gradualism. The finding of “Rucinolithus” morphotypes, very similar to the Cretaceous taxa R. terebrodentarius and R. terebrodentarius youngii, is intriguing. They might represent nannoliths strongly affected by a recurrent “Lazarus effect” or be diagenetic artifacts or of bacterial bioprecipitation.     

Dinoflagellate cysts,sea level changes and planktonic foraminifers across the Cretaceous-Tertiary boundary at El Haria,northwest Tunisia

Dinoflagellate cysts and planktonic foraminifers have been studied from the Cretaceous/Tertiary (K/T) boundary interval at El Haria (northwest Tunisia). A high-resolution integrated biostratigraphy is presented. The K/T boundary is drawn at the level of extinction of Cretaceous planktonic foraminifers and is coincident with the first occurrence of the dinoflagellate cyst species Danea californica. The final extinction of planktonic foraminifers is foreshadowed by a reduction in their total abundance some 5 kyr earlier at the base of the boundary clay. This reduction is coeval with reported anomalies in siderophyle elements and δ¹³C-values in the same area. Dinoflagellate cysts do not show accelerated rates of extinction at K/T time. Associations of dinoflagellate cysts, however, change drastically and parallel changes in relative numbers of sporomorphs (spores and pollen) and in the quantity of land-derived organic matter. Jointly, these changes reflect a rapidly falling sea level during the final 17 kyr of the Mesozoic which culminates at the level of the K/T boundary. This steep sea level fall at K/T time represents a peak regressive pulse at the end of the well-documented latest Cretaceous regressive trend. This short-term sea level fall might show to be a wide-spread phenomenon which could have caused an excess shrinking of the already reduced areal extent of marginal seas. Since deep waters in Cretaceous oceans were primarily produced in shallow marginal seas, the rate of formation of deep water might have been minimized at K/T time. Minimum rates of formation of deep water might have curtailed the slow upward mixing of relatively cool and nutrient-rich deeper water through which the thermocline weakened and surficial waters became depleted in nutrients. Consequently, phytoplankton productivity rapidly diminished which, in combination with a weakened thermal gradient, pushed the highly depth-stratified Cretaceous planktonic foraminiferal fauna to extinction over a period of time of some 5 kyr. Guembelitria cretacea was the sole planktonic foraminifer which could accommodate to the low productivity conditions. The oscillating rise in sea level at the beginning of the Cenozoic reinforced the upward mixing of relatively cool and nutrient-rich deeper water, steepened the thermocline and replenished the photic layer with nutrients. Concomitant niche-differentiation in the photic layer progressively stimulated morphological innovation amongst early Cenozoic planktonic foraminifers. The final return of normally-sized planktonic foraminifers and of stable and well-balanced dinoflagellate cyst associations at about 125 kyr after the K/T boundary seems to indicate that primary productivity and niche differentiation in the photic layer begin to revert to optimum levels. The earliest Cenozoic planktonic foraminiferal species Globoconusa minutula and Parvularugoglobigerina fringa are thought to have developed from a benthic foraminiferal species rather than having a planktonic ancestry.     

Foraminiferal assemblages of the Bric della Muda laminites (Nizza Monferrato, Piedmont): Proxies of cyclic palaeoenvironmental changes in the early Messinian of Northwestern Italy

Foraminiferal assemblages in laminites cropping out at the Bric (i.e. Hill) della Muda (Nizza Monferrato, Piedmont, Northwestern Italy) document deep marine conditions during the early Messinian, spanning a time-interval approximating, or slightly wider than the stratigraphic range of Globorotalia nicolae (6.82-6.72 Ma). Fluctuations in abundance of planktonic warm-water oligotrophic taxa and cold-water eutrophic species show a cyclical pattern, very comparable to variations measured in cyclically-bedded formations of the pre-evaporitic Messinian in the Mediterranean area. A subtropical climate with cyclic warmer and cooler episodes, characterized by surface water stratification and vertical mixing in the water column, respectively, is also documented. A depositional depth close to or larger than 1000 m is inferred on the basis of planktonic assemblages yielding also the deep planktonic Hastigerinella digitata and of very high P/(P + B) ratios. Anoxic or strongly dysoxic bottom conditions are indicated by the absence or rareness of benthic foraminifers, which are represented by taxa tolerant of low-oxygen or high organic content (Bolivina pseudoplicata, Chilostomella oolina, Globobulimina affinis). A slight decrease in P/(P + B) ratios, and the presence of rare shallow-water forms in the uppermost layers suggest a mild dysoxia and a probable shallowing, when compared with coeval events in Northern Apennines and Southern Greece sections.     

Late Miocene biota from the Abad Member of the Carboneras-Nijar Basin (Spain,Andalusia): A bathyal fossil assemblage pre-dating the Messinian salinity crisis

Marly sediments of the early Messinian Abad Member of the Turre Formation from the northeastern sector of the Carboneras-Nijar Basin (southern Spain) have yielded a rich fossil assemblage, of which 60 taxa are documented herein. Besides nannoflora and microfauna, this assemblage includes the first autochthonous macrofauna described from the Abad Member. Based on the calcareous nannofossil assemblage, in particular the occurrence of the zonal index taxon Amaurolithus primus, the sediments are assigned to the Mediterranean calcareous nannofossil zone CNM17, corresponding to the latest Tortonian to earliest Messinian interval. This matches the age range generally reported for the Abad Member. Palaeoecological evidence from calcareous nannofossils (20 autochthonous taxa), planktic and benthic foraminifera (12 taxa), Porifera (3 taxa), Octocorallia (Keratoisis), Serpulidae (4 taxa), Bivalvia (5 taxa), Gastropoda (2 taxa), Brachiopoda (7 taxa), Cirripedia (Faxelepas) and Vertebrata (5 taxa) indicates an upper bathyal environment with an influx of neritic elements for the Abad Member near Carboneras. Additionally, several faunal components may represent allochthonous/parautochthonous elements from adjacent habitats, which were transported into the deep marine setting by turbiditic mass flows. Although similarities exist, the fossil assemblage from the marls is compositionally significantly different from the biota previously documented from a nearby exposed olistostrome, the ‘red breccia’. Similar fossil assemblages from the Mediterranean have so far mainly been reported from the Pliocene-Pleistocene of southern Italy and Greece. The Carboneras fauna thus adds to our knowledge of the development of these habitats and their biota prior to the Messinian salinity crisis. Beyond the novel palaeoenvironmental data, the range of the dyscoliid brachiopod Ceramisia meneghiniana, previously known only from the Pliocene of Italy, is extended to the Miocene of Spain. The cirripede crustacean Pycnolepas paronai De Alessandri, 1895 is transferred to the hitherto monospecific genus Faxelepas Gale, 2015, whereby the range of the latter (previously Maastrichtian to Danian) is extended to the late Miocene.     

Quantitative calcareous nannofossil biostratigraphy of the subsurface Pliocene sequence,north-east Nile Delta,Egypt

Detailed quantitative calcareous nannofossil biostratigraphy was carried out on a subsurface lower–upper Pliocene succession (Kafr El Sheikh Formation) in three offshore wells (Ras El Barr-1, Bougaz-1 and Bougaz East-1), north-east Nile Delta area, Egypt. The standard zonations are easily applied in these sediments and additional biohorizons have been adopted in this study. For early to late Pliocene interval, the following five bioevents are considered reliable: last occurrences (LOs) of Discoaster surculus, D. tamalis, Reticulofenestra pseudoumbilicus and Amaurolithus tricorniculatus and first occurrence of D. asymmetricus. The LO of R. pseudoumbilicus was used to detect the early/late Pliocene boundary in the three studied wells. In Bougaz-1-Well, the LO of D. intercalcaris was used to approximate the Miocene/Pliocene boundary. The calcareous nannofossils are moderate to good preserved. Lower–upper Pliocene sediments are dominated by small-sized reticulofenestrids (R. minuta), Pseudoemiliania lacunosa, Helicosphaera carteri and H. kamptneri. Large size (>7 μm) R. pseudoumbilicus is recorded. Discoaster species is rarely represented. No nannofossils were found in the top part of the Kafr El Sheikh and the overlying Wastani Formations.     

Calcareous nannofossil biostratigraphy of the Thomel Level (OAE2) in the Lambruisse section, Vocontian Basin, southeast France

The Thomel Level of the Lambruisse section in the Vocontian Basin (southeast France), which is marked by intercalations of black shales and organic-rich marls, accumulated during the oceanic anoxic event 2 (OAE2) occurring in the Cenomanian-Turonian (C-T) boundary interval. Calcareous nannofossil biostratigraphic investigation of this interval revealed a total of five nannofossil zones, corresponding to the UC3-UC8 zones (Middle Cenomanian-Middle Turonian) as defined by Burnett. Biostratigraphically important taxa observed in the section include Cretarhabdus striatus, Axopodorhabdus albianus, Lithraphidites acutus, Corollithion kennedyi, Helenea chiastia, Quadrum gartneri, Q. intermedium, Eiffellithus eximius, Eprolithus octopetalus and E. eptapetalus. The two nannofossil events commonly used in the delineation of the C-T boundary, namely the LO of H. chiastia and the FO of Q. gartneri, occur less than 2 m apart in the studied section. These two bioevents define the limits of the UC6 nannofossil Zone and occur within the Whiteinella archaeocretacea foraminifer Zone. Previous litho- and chemostratigraphic analyses indicate that the δ¹³C profile of the section corresponds well with changes in lithofacies and fluctuations in the total organic carbon (TOC) and calcium carbonate content of the section. Initial increase in the δ¹³C values occurs within the UC3-UC4a undifferentiated zone, coinciding with the onset of the deposition of the organic-rich sediments of the Thomel Level and a drastic decline in the CaCO₃ values. The plateau of high δ¹³C values, on the other hand, occurs within the UC5 zone, between the LO of C. kennedyi and the LO of H. chiastia (and FO of Q. gartneri). This interval of high δ¹³C values also corresponds to the interval of high TOC and low CaCO₃ values. The integrated nannofossil, planktonic foraminifer and δ¹³C data provide a precise biostratigraphic and chemostratigraphic framework of the C-T boundary in the Lambruisse section that can be used in future studies in the Vocontian Basin and allow correlations with other well-studied C-T boundary sections.     

Long-term upwelling evolution in tropical and equatorial Pacific during the last 800 kyr as revealed by coccolithophore assemblages

The coccolithophore assemblages in two ODP Sites (1237 and 1238) are studied in order to reconstruct the paleoenvironmental conditions in the tropical and equatorial Pacific during the last 800 kyr. Both ODP Sites are located in the two most significant upwelling zones of the tropical and equatorial Pacific: Peru and Equatorial upwelling, respectively. The two sites are considered to have had similar evolutions. The coccolith relative abundance, the nannofossil accumulation rate (NAR) and the N ratio (namely, the proportion of < 3 μm placoliths in relation to Florisphaera profunda) allow us to identify three different intervals. Interval I (0.86-0.45 Ma) and interval III (0.22-0 Ma) are related to weak upwelling and weak Trade Winds, as suggested by coccolithophore assemblages with low N ratios. Interval II (0.45-0.22 Ma), characterized by dominant Gephyrocapsa caribbeanica and very abundant “small” Gephyrocapsa and Gephyrocapsa oceanica, is conversely related to intense upwelling and enhanced Trade Winds.     

Integrated biostratigraphy for the Santonian/Campanian boundary interval,the Kurdistan Region,northeast Iraq

The first high-resolution integrated biostratigraphic study for Santonian/Campanian sediments of the Tabin section in the Kurdistan Region, northeast Iraq is provided. The study, based on 28 closely spaced samples, combines data from planktic foraminifers (25 species), calcareous nannofossils (32 species) and two ammonite genera in the Kometan Formation, marking the Santonian/Campanian boundary (S/C boundary) in the Kurdistan Region. In the absence of the crinoid Marsupites testudinarius, the proposed boundary marker, secondary markers such as calcareous nannofossils, planktic foraminifers and ammonites, have been used to establish a multi-stratigraphic biozonation for the late Santonian–early Campanian duration. Based on the occurrences of calcareous nannofossils, three biozones are identified — Lucianorhabdus cayeuxii (late Santonian), Calculites obscurus (latest Santonian–earliest Campanian), and Broinsonia parca parca (early Campanian). Seven calcareous nannofossil bioevents and three planktic foraminiferal bioevents are also identified. The Santonian/Campanian boundary is marked by: (a) the LO (Last Occurrence) of the planktic foraminifera D. asymetrica, (b) the FOs (First Occurrence) of the calcareous nannofossil species B. parca parca and B. parca constricta, (c) the extinction of several planktic foraminiferal species of Dicarinella and Marginotruncana, (d) the abundance and diversification of the planktic foraminifera genera, Globotruncana and Globotruncanita at the beginning of the Campanian, and (e) the disappearance of the ammonite genus Texanites, 0.5 m below (i.e., at 19 m) the disappearance of all Dicarinella and Marginotruncana species in the study section. Similar to several other Tethyan sections, the FO of B. parca parca is above the LOs of D. concavata and D. asymetrica; the LO of D. asymetrica is used here to mark the S/C boundary     

Calcareous nannofossil biostratigraphy and paleoclimatology of the Paleocene succession,Tenida area,Western Desert,Egypt

This study is a preliminary quantitative analysis of Paleocene calcareous nannofossil assemblages of the Tenida area (Egypt) in order to establish a detailed biostratigraphic framework as well as to reconstruct the paleoclimatic trends. A total of 48 samples with an average sample spacing of 1.5 m allowed the identification of 63 calcareous nannofossil species belonging to 19 different genera. The preservation of the studied samples varies from poor to moderate and is characterized by the frequent presence of small frangible placoliths, and nannoliths. This study recognizes three calcareous nannofossil biozones in the Danian-Thanetian time interval; Chiasmolithus danicus (NP3) Zone, Ellipsolithus macellus (NP4) Zone, and Heliolithus kleinpellii (NP6) Zone. Moreover, the multivariate statistical analysis of the calcareous nannofossil communities reveals a relationship between the distribution of these nannofossil assemblages and variations in paleoclimatic trends. Accordingly, the relative abundances of Coccolithus pelagicus in addition to nine calcareous nannofossil genera along with the diversity and preservation indices of calcareous nannofossil elements have been used to elucidate changes in paleoclimatic trends. Based on the cyclic change from cold to warm climates, it was possible to subdivide the Paleocene Period recorded in the Tenida section into four paleoclimatic intervals. The oldest is a global cooling trend spanning 2.01 Myr long, starting in the early Paleocene (Danian) during the deposition of the lower part of the Kharga Shale Member. This cooling trend is followed by a ～ 0.56 Myr warming trend during deposition of the middle part of the Kharga Shale Member that was followed by a return to a cooling mode, with an estimated duration of roughly 1.67 Myr. The last interval includes a 0.39 Myr long period at the Selandian/Thanetian boundary interval, which is dominated by a global warming trend during deposition of the upper part of the Upper Kharga Shale Member.     

Calcareous nannofossil biostratigraphy and paleoecology of the Cretaceous–Tertiary transition in the central eastern desert of Egypt

The Gebel Qreiya and nearby Wadi Hamama sections of the central Eastern Desert are among the most complete K/T boundary sequences known from Egypt. The two sections were analyzed spanning an interval from l.83 Myr below to about 3 Myr above the K/T boundary. A 1-cm-thick red clay layer at the K/T boundary at Gebel Qreiya contains an Ir anomaly of 5.4 ppb. The high-resolution study and well-preserved nannoflora provide good age control and the first quantitative records of calcareous nannofossil assemblages for paleoecological interpretations across the K/T transition in Egypt. Four zones (Micula murus, Micula prinsii, NP1, and NP2) were distinguished and correlated with other nannofossil and planktonic foraminiferal zonations that are broadly applicable for the eastern Tethys region. Latest Maastrichtian assemblages are abundant and diverse, though Cretaceous species richness progressively decreased across the K/T boundary. Dominant species include Arkhangelskiella cymbiformis, Micula decussata and Watznaueria barnesae, with high abundance of dissolution-resistant M. decussata reflecting periods of high environmental stress. Thoracosphaera blooms mark the K/T boundary and are followed by an acme of the opportunistic survivor Braarudosphaera bigelowii, the first appearance of the new Tertiary species Cruciplacolithus primus, and an acme of Coccolithus cavus/pelagicus. These successive abundance peaks provide the basis for subdivision of the Early Danian Zones NP1 and NP2 into five subzones. Correlation of selected nannofossil taxa from the Egyptian sections with those from various onshore marine and deep-sea sections provides insights into their paleoenvironmental and paleoecological affinities.     

Did the Late Paleocene thermal maximum affect the evolution of larger foraminifers? Evidence from calcareous plankton of the Campo Section (Pyrenees,Spain)

The larger foraminifer turnover (LFT), which marks the base of the Ilerdian stage, may be related to the Late Paleocene Thermal Maximum (LPTM), or be at least nearly coeval with that climatic event. Thus, the impact of the LPTM may have been greater than hitherto realised, having also affected mid-latitude shallow-marine biota. This conclusion has been reached after a re-study of the calcareous plankton of the uppermost Paleocene and lowermost Eocene interval of the Campo section in the central southern Pyrenees. Campo is an important reference section because it contains larger foraminifers, planktic foraminifers and calcareous nannofossils, and their co-occurrence was used to intercalibrate their respective zonal schemes. Previous studies at Campo placed the onset of planktic foraminiferal Zone P5 near the base of the Ilerdian, and the calcareous nannofossil NP9/NP10 chronal boundary (sensu Bybell, L.M., Self-Trail, J.M., 1995. Evolutionary, biostratigraphic and taxonomic study of calcareous nannofossils from a continuous Paleocene/Eocene boundary section in New Jersey. US Geol. Surv. Prof. Pap. 1554, pp. 1–36) not less than 150 m above the Ilerdian lower limit. By these estimates, the LPTM (known to have occurred in the middle part of Zone P5 and just before the NP9/NP10 boundary) would be an event much younger than the LFT.However, our reexamination of planktic foraminifers suggests that the base of the Ilerdian is probably situated at the middle of Zone P5 (a possibility proposed by Hillebrandt in 1965, but denied by later authors). For instance, Morozovella occlusa has been found for the first time in the Campo section. Its Last Appearance Datum (LAD), which in the Pyrenees was approximately coeval with that of Morozovella velascoensis (event used to place the top of Zone P5), has been identified in beds situated less than 70 m above the base of the Ilerdian. Such thickness represents a time span of a similar magnitude as the one which separated the LPTM and the LAD of M. occlusa in the deep-water hemipelagic succession of the Basque Basin, in the western Pyrenees. Autochthonous calcareous nannofossils are neither abundant nor well preserved in most of the studied interval, with Rhomboaster bramlettei (the marker of the base of Zone NP10) being extremely rare in lower and middle Ilerdian beds, a fact that makes it very difficult to fix the position of the NP9/NP10 boundary in the Campo section. However, the bases of zones NP9 and NP11 have been located, and they support the zonation with planktic foraminifers. These new data suggest that the LFT and the LPTM may have been coeval or nearly so, a possibility reinforced by correlation with sections of the Basque Basin.Specialists of larger benthic foraminifers can easily delineate the LFT in shallow water carbonate successions of the Tethys domain, and they propose to place the Paleocene/Eocene boundary at the base of the Ilerdian stage. On the other hand, the deep benthic extinction event (BEE) is a major global biotic turnover in the bathyal and abyssal realms, while the ∂13C excursion (CIE) is an excellent tool for correlation between marine and terrestrial records. Therefore, the synchrony or near synchrony postulated here between the LFT, BEE and CIE (all of them probably related to the LPTM) would argue strongly in favour of these events as the criterion to officially redefine the Paleocene/Eocene boundary.