Reticulofenestra Pseudoumbilicus Research Articles

Calcareous nannofossils biostratigraphy of well Uche 1, Offshore Lagos, Eastern Dahomey Basin, South Western Nigeria

Well Uche 1 drilled in the offshore of Dahomey Basin was biostratigraphically analyzed, based on its calcareous nannofossils content. Thirty analyzed samples were collected from the Well at an interval range of 20m at a depth of 1284m- 1860m. The microscopic examination of the processed samples was carried out (using simple smear method) and this was found useful in the identification of the different biostratigraphic zones present. Moreover, it is equally found useful in age determination. In all, fifteen (15) calcareous nannofossil species (Braarudosphaera bigelowii, Calcidiscus leptoporus, Coccolithus nitescens, Coccolithus pelagicus, Coronocyclus nitescens, Discoaster deflandrei, Discoaster druggii, Discoaster sp (6rays), Helicosphaera cateri,Pontosphaera multipora, Reticulofenestra haqii (3-5 microns), Reticulofenestra pseudoumbilicus (5-7 microns), Reticulofenestra pseudoumbilicus (>7 µ), Sphenolithus moriformis, Triquetrorhabdulus carinatus) were identified and used for biozonation and identification of significant time surfaces. The distribution of the calcareous nanofossil species in the well enabled the establishment of zones belonging to the Early Miocene; NN2 zone. The most abundant calcareous nannofossils identified are Triquetrorhabdulus carinatus, Cyclicargolithus abisectus and Discoaster druggi. Two biozones of calcareous nannofossils were identified from the well as well as three significant surfaces.

Calcareous microfossil biostratigraphy of Upper Miocene to Pliocene deposits of the Sinú-San Jacinto Belt, Caribbean region of Colombia

A compilation of previous biostratigraphic studies conducted in Upper Miocene to Pliocene deposits from the Caribbean region of Colombia reveals a predominant reliance on mollusks and benthic foraminifera for age determinations, with planktonic microfossils being less explored. To contribute to this biostratigraphic background, we have performed biostratigraphic analyses of calcareous nannoplankton, an oceanic planktonic micropaleontological group, on 71 mudrock samples from two stratigraphic sections located in the Sinú-San Jacinto Belt (SSJB). The Canalete stratigraphic section, outcropping in the southwestern portion of the belt, yielded the biostratigraphic markers Discoaster bergenii, Discoaster berggrenii, Discoaster surculus, and Reticulofenestra pseudoumbilicus. This assemblage, typical of the Zone NN11, indicates that the 50-m-thick section was accumulated during the Late Miocene, sometime between the late Tortonian and late Messinian. The ANH-Conuco-1 well, a cored stratigraphic section drilled in the northeastern area of the belt, also contained the above-mentioned biostratigraphic markers as well as Amaurolithus primus-delicatus, Ceratolithus acutus, Discoaster quinqueramus, Helicosphaera sellii, and Reticulofenestra rotaria. These taxa suggest that the stratigraphic interval between 754.1 m and 58.4 m in this cored section is enclosed within the zones NN11 and NN12, ranging in age from Late Miocene to Early Pliocene (late Tortonian to earliest Zanclean). Reworked nannofossils Cyclicargolithus floridanus, Discoaster deflandrei, Sphenolithus disbelemnos, and Sphenolithus heteromorphus were observed in both localities, implying the redeposition of Lower to Middle Miocene and, possibly, Paleogene marine sediments. This is supported by previous documentation of reworked planktonic foraminifera in Upper Miocene to Pliocene deposits from the Caribbean region of Colombia. The identified calcareous nannoplankton assemblages not only provide additional constraints on the existing biostratigraphic data of planktonic foraminifera in this region, but also aid in the correlation of both analyzed stratigraphic sections with other Upper Miocene deposits in northwestern South America.

THE DISTRIBUTION RANGE OF CALCAREOUS NANNOFOSSIL SPECIES <em>RETICULOFENESTRA PSEUDOUMBILICUS</em> IN THE MIOCENE: AN EXAMPLE OF ECOLOGICAL INFLUENCE ON EVOLUTIONARY DEVELOPMENT

Reticulofenestra pseudoumbilicus is a Neogene calcareous nannofossil species whose highest stratigraphic occurrence (Top) is a reliable biohorizon in the Pliocene, calibrated at 3.82 Ma. The species is present in the stratigraphic record from at least the Middle Miocene, within an interval around the biohorizon Top Sphenolithus heteromorphus, calibrated at 13.53 Ma, but its lower distribution range is not precisely delineated. The study of nannofossil assemblages in sediment cores from Integrated Ocean Drilling Program IODP Site U1338 (eastern equatorial Pacific) indicates a lower stratigraphic position for the evolutionary emergence (Base) of R. pseudoumbilicus, detected in the Early Miocene with an estimated age of 16.46 Ma. This age results from a new astronomically tuned chronology, which dates the deepest sediments at Site U1338 to 16.67 Ma. Base R. pseudoumbilicus is followed above by a temporary disappearance of the taxon until a re-entrance after ~3 Myr. This lengthened stratigraphic range has been confirmed by data from other locations at low and mid-latitudes in the Atlantic. The distribution range of R. pseudoumbilicus, lasting ~13 Myr during the Neogene, is thus characterized by a variable pattern of repeated occurrences and disappearances. Comparison to benthic foraminifera δ18O and δ13C records suggests a control by global climatic/environmental conditions on these events, particularly by temperature variations. The recurrent presence of R. pseudoumbilicus at stratigraphically different intervals could represent an example of iterative evolution, expressed as repeated speciation events that are in part influenced by complex external factors related to the dynamic climate and environmental evolution during the Miocene.

Calcareous nannofossils from the middle/upper Miocene succession of Pécs-Danitzpuszta, southern Hungary: cosmopolitan Paratethys and endemic Lake Pannon assemblages

Quantitative analyses on calcareous nannofossils were carried out on 109 middle/late Miocene (Sarmatian/ Pannonian) samples from the section at Pécs-Danitzpuszta sand pit (Hungary). The lower part of the section, which can be assigned to the Sarmatian, contains normal marine low-diversity assemblages dominated by Calcidiscus leptoporus, Reticulofenestra pseudoumbilicus, Sphenolithus moriformis and Syracosphaera spp. accompanied by didemnid ascidian spicules (Perforocalcinela fusiformis). The middle/late Miocene (Sarmatian/Pannonian) boundary is characterized by the last occurrences of normal marine calcareous nannofossils. The upper part of the section (Pannonian) can be subdivided into intervals characterized by monospecific endemic nannofossils Isolithus spp. and ascidians, respectively. A short interval with common endemic coccoliths belonging to the family Noelaerhabdaceae (Bekelithella echinata, Noelaerhabdus bozinovicae, N. jerkovici, Praenoelaerhabdus banatensis) in the upper part of the profile was also documented. The drastic change in nannofossil assemblages at the Sarmatian/Pannonian boundary is a result of paleoenvironmental stress caused by the isolation of the Central Paratethys from the Eastern Paratethys.

High‐resolution Pliocene–Pleistocene calcareous nannofossil distribution and palaeoenvironmental changes in the northwest Nile Delta, Egypt

The Pliocene–Pleistocene sequences in the Nile Delta are of immense economic significance due to their hydrocarbon potential. Hence, a better understanding of the time-calibrated basinal palaeoenvironmental changes is essential to improve the hydrocarbon recovery. A total of 182 sub-surface samples from the Sapphire-DC well in the offshore north-western part of the Nile Delta were analysed to reveal changes in calcareous nannofossil assemblage composition and palaeoenvironments during the late Miocene–Pleistocene (5.44–0.43 Ma). Sixteen marker bioevents and nine biozones are identified for the first time. The absence of Ceratolithus acutus suggests a hiatus at the Messinian–Zanclean (Miocene–Pliocene) boundary. The studied interval is marked by the dominance of five species; Pseudoemiliania lacunosa (24%), small Gephyrocapsa sp. (20%), Helicosphaera kamptneri (11%), Reticulofenestra minutula (10%) and Calcidiscus leptoporus (6%). Based on their distribution patterns, six intervals (Intervals 0 to 5) are identified. Throughout the study interval, cooler waters (except during Interval 0; Messinian Salinity Crisis, MSC, 5.44–5.26 Ma) and eutrophic conditions persisted within a shallow hemipelagic and near-continental setting, marked by moderate-to-high terrigenous input (more for Intervals 4 and 5; ˜2.73–0.42). Additionally, low species diversity and high species dominance are identified, suggesting a stressed environment. Species diversity shows a gradually declining trend, up section, whereas species dominance correspondingly increases. Interval 0 (MSC) is dominated by warm water species of Sphenolithus abies and Helicosphaera kamptneri. The cool water species, Reticulofenestra pseudoumbilica, and small Gephyrocapsa dominate in Interval 1; small Gephyrocapsa dominates in Interval 2. Interval 3 is marked by the deepening of the basin with a brief introduction of warm, somewhat oligotrophic and open-ocean waters. In the middle of this interval (at 3.73 Ma; the Early–Late Pliocene boundary), an abrupt decrease in species diversity with a corresponding increase in species dominance suggests deteriorating conditions. Interval 3 also encompasses the mid–late Pliocene warming period, which in the Nile Delta is marked by cooler waters. Intervals 3–5 are dominated by P. lacunosa, suggesting a continuation of cool waters and eutrophic conditions. Hence, throughout the study interval, cooler waters (except during the MSC) and eutrophic conditions within in a shallow hemipelagic and near-continental setting are inferred with moderate-to-high terrigenous input and low species diversity and higher species dominance, suggestive of stressed environmental conditions.

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.

Neogene calcareous nannofossils from San José Island, Baja California Sur, Mexico

A study of calcareous nannofossils was carried out in two sedimentary columns from the Palma Sola Basin, San Jose Island, Baja California Sur, Mexico, in order to establish the age of these deposits and to place them in a chronostratigraphic context within the evolution of the Gulf of California. A total of 66 species were identified and based on the presence of small Gephyrocapsa, Reticulofenestra minuta, R. minutula, R. haqii, Pseudoemiliania lacunosa and P. ovate, an age of ≈3.6 Ma for Palma Sola I and at least for most part of the Palma Sola II equivalent to the standard NN15 Reticulofenestra pseudoumbilica Zone is assigned. The top of the Palma Sola II column does not contain reticulofenestrids. If its absence is stratigraphic, a younger age could be inferred; however, considering also the absence of zonal indicators, is tentatively, at least ≈ 3.6 Ma. On the basis of the abundance of Coccolithus pelagicus s.l., small to medium Reticulofenestra spp., and small Gephyrocapsa and Helicosphaera spp., a paleoenvironment influenced by coastal upwelling is inferred.

LATE MIOCENE CALCAREOUS NANNOFOSSIL STRATIGRAPHY AND BIOEVENTS CORRELATION: KALIDONIA CASE SECTION (NW CRETE, GREECE)

Calcareous nannofossils are widely used for biostratigraphic correlations. Quantitative approaches enable better understanding of reliability of bioevents. In order to refine the late Miocene stratigraphy ofNW Crete, the deposits of Kalidonia basin along its type section are here investigated. It was possible to distinguish the Tortonian/Messinian boundary by NNlla & NNllb, CN9a & CN9b, MNNlla & MNNllb biozones. Reticulofenestra pseudoumbilicus PB (Paracme Beginning) and R. rotaria FO (First Occurrence) proved to act as additional significant biohorizons improving the stratigraphie evolution of the studied paleobasin and providing a tight biochronologic framework. The Kalidonia section fully covers an undisturbed marine depositional cycle from the upper Tortonian to upper Messinian, where a predominant deep water fades (DWF) is followed by transitional sediments (TF) and the sequence closes at the top by a reefal-bioclastic fades (RF) relative to the 'Calcare di Base ' in Italy indicating the 'Messinian Salinity Crisis Event.

Facies and Sequence Stratigraphy Analyses of Klasaman Formation in the “X Well”, Northern Salawati Basin, Papua, Indonesia

The “X Well” is located in the Salawati Basin which is part of Western Papua. The interval of study is the Klasaman Formation that is characterized by thick sediment intercalated sandstones and shales. The movement of Sorong Fault strongly controlled the sedimentation of this formation. This study is very important to give a contribution for developing exploration prospect by predicting reservoir distribution since localized facies change may mark the distribution of sandstones. The current study aims: 1) to define the age of Klasaman Formation; 2) to define the vertical facies; 3) to define the sequence stratigraphy; and 4) to predict the lateral change of facies. Five nannofossil datum planes are found throughout the interval and cover the age Late Miocene to Early Pliocene. LO Sphenolithus abies points the age 3.65 Ma, LO Reticulofenestra pseudoumbilicus points the age 3.79 Ma, FO Pseudoemiliania lacunosa points the age 4 Ma, LO Discoaster quinqueramus and LO Discoaster berrgrenii point the age 5.59 Ma and Top of small Reticulofenestra Interval points the age 7.167 Ma. They define the NN11 up to NN16 Martini’s zonation. The age of Klasaman Formation is known as the uppermost Late Miocene to the Early Pliocene. Four facies can be identified, namely Upper Shoreface, Lower Shoreface, Offshore Transition and Offshore. The upper shoreface facies is characterized by thick and clean sandstones, about 2.41 - 20.64 meters thick, while the lower shoreface facies consists of predominantly very fine to fine-grained sandstones intercalated by siltstones and claystones. The offshore transition facies is marked by thick claystones and siltstones intercalated with thin sandstones, whilst the offshore facies is marked by thick laminated claystones. Nine Parasequences 4th order can be identified within study interval, namely Progradational Parasequence-1 to 2, Retrogradational Parasequence-3, Progradational Parasequence-4 to 6, Retrogradational Parasequence-7 to 9. They are bounded by Sequence Boundary-1 to 8. The upper shoreface sandstones of Parasequence-4 to 9 can be potential reservoir rocks in the Klasaman Formation since the sandstones are very thick and clean. The sediments of Klasaman Formation have been sourced from elevated highland in the northeast area, so the upper shoreface sandstones have changed become the offshore claystones from northeast to southwest. High sedimentation rate and rapid subsidence of the basin mark the deposition of Klasaman Formation especially during the deposition of Parasequence-6 to 9 as a result of Sorong Fault tectonics.

HIGH RESOLUTION BIOSTRATIGRAPHY AND PALEOECOLOGY OF THE EARLY PLIOCENE SUCCESSION OF PISSOURI BASIN (CYPRUS ISLAND)

The Pissouri basin (Cyprus Island) corresponds to a small tectonically controlled depression elongated NNW-SSE and widening southward in the direction of the deep Mediterranean domain. In the centre of the basin, the section Pissouri South, about 100 m thick, consists of well-preserved cyclic marine sediments including laminated brownish layers alternating with grey homogeneous marls. Plankton biostratigraphy (calcareous nannofossil and planktonic foraminifera) revealed a remarkable number of biovents bracketing the Zanclean-Piacenzian boundary. In particular the Highest Occurrence (HO) of Reticulofenestra pseudoumbilicus suggests the presence of NN14/15-NN16 nannofossil biozone boundary, dated at 3.84 Ma. Additionally the defined planktonic foraminiferal MPL3-MPL4a and MPL4a-MPL4b zone boundaries point to ages between 3.81 and 3.57 Ma, in Pissouri North section. Zanclean/Piacenzian boundary (3.6 Ma) is placed at 75.8 m from the base of the section, considering Discoaster pentaradiatus top paracme (3.61 Ma) and Globorotalia crassaformis first influx (3.6 Ma) bioevents. The cyclically developed sapropelic layers around the Zanclean – Piacenzian boundary suggest a climate characterized by a period of warm temperate conditions and a highly stratified water column that occurred at times of precession minima.

Ichnological analysis of the Upper Miocene in the ANH-Tumaco-1-ST-P well: assessing paleoenvironmental conditions at the Tumaco Basin, in the Colombian Pacific

Tumaco is a frontier basin located on the SW Colombian Pacific coast. It is composed of a thick siliciclastic sequence up to reach 10,000 m-thick. In recent years, the National Hydrocarbon Agency-ANH has promoted new exploration wells in order to understand the sedimentary dynamic and its relationship with petroleum systems. One of them, the ANH-Tumaco-1-ST-P well has ∼3000 m (12,000 feet). We carried out sedimentological, geochemical, and micropaleontological detailed analyses with special attention to the ichnology on a 55 m-cored interval (from 1695.3 to 1640.4 m = 5563–5382 ft) in order to assess paleoenvironmental conditions. Beds are composed of green and gray mudrocks interbedded with lithic sandstones and fine-grained tuffs. Calcareous microfossil assemblages defined by the recovery of Uvigerina carapitana, Uvigerina laviculata, Uvigerina pigmaea, Globigerina woodi, Globigerionoides obliquus, Discoaster bellus gr., Catinaster coalitus, Reticulofenestra pseudoumbilicus and Sphenolithus abies indicated a Tortonian age, between CN6/CN7 biozones. Six sedimentary facies were identified: (1, 2) massive and laminated mudrocks, (3, 4) massive and normal-graded sandstones, (5) heterolithic beds, and in some cases (6) sandstones with soft-deformation structures. These rocks were accumulated in a shallowing platform-prodelta environment with continuous volcanic influence. Ichnotaxonomic analysis, conducted for the first time in the Colombian Pacific, allowed the identification of eighteen ichnogenera: Alcyonidiopsis, Asterosoma, Chondrites, Conichnus, Cylindrichnus, Diplocraterion, Ophiomorpha, Palaeophycus, Phycosiphon, Planolites, Rhyzocorallium, Schaubcylindrichnus, Scolicia, Siphonichnus, Taeinidum, Teichichnus, Thalassinoides, and Zoophycos. The ichnological association belongs to the archetypal Cruziana ichnofacies and its “distal” expression. By integrating lithofacies and ichnological results, two segments have been distinguished: 1) the lower one (1695.3–1677.1 m) dominated by massive and laminated mudrocks and 1 to 6 ichnofabric indexes and, 2) the upper segment (1677.1–1640.4 m) characterized by the increase of the sandstone facies, and ichnofabric indexes from 1 to 5. Along these segments, four ichnofabrics have been identified: 1) Phycosiphon-Planolites, 2) Planolites-Thalassinoides, 3) Zoophycos-Chondrites, and 4) Phycosiphon-Thalassinoides, reflecting stable sedimentary conditions with low-moderate energy, low-moderate sedimentation rates, and dominant aerobic facies. Minor variations in these parameters (sedimentation rate, energy conditions, substrate consistency, oxygenation and organic matter), however, induced changes in the macrobenthic tracemaker community, and consequently in the registered trace fossil assemblages.

Nannoplankton calendar: Applications of nannoplankton biochronology in sequence stratigraphy and basin analysis in the subsurface offshore Nile Delta, Egypt

A comprehensive nannoplankton biozonation of the Pliocene-Pleistocene succession of off-shore Nile Delta has been recorded from two wells, namely Baltim-1 and NDOB-1, in the present contribution. The biozonation is relied the identification of 8 nannoplankton biozones and their associated bioevents. These biozones are Pseudoemiliania lacunosa Zone (NN19), Discoaster brouweri Zone (NN18), Discoaster pentaradiatus Zone (NN17), Discoaster surculus Zone (NN16), Reticulofenestra pseudoumbilicus Zone (NN15), Discoaster asymmetricus Zone (NN14), Ceratolithus rugosus Zone (NN13) and Amaurolithus tricorniculatus Zone (NN12) as arranged from top to base. The Pliocene-Pleistocene boundary is placed near to the top of D. surculus Zone (NN16). The lower boundary of the Pliocene is placed within the A. tricorniculatus (NN12). The recognized bioevents are used to calculate the sedimentation rates (SRs) and to delineate their relative variations versus the depth. The relative variations of the SR values were interpreted in accordance with the history of fluvial fresh water supply in the Delta region since the early Pliocene. The relationship between the values of the SR and the potential occurrences of hydrocarbon sources (organic matter oxic preservation) and reservoir (coarser clastics accumulation) rocks in the studied succession has been clarified. Likewise, the possible relationships of the SR values, history of fresh water input in the Nile Valley and the sapropel formation mechanism has been discussed. The relative variations of SRs versus the depth have been interpreted in a sequence stratigraphic framework, which led to identification of three correlatable genetic sequences in the studied succession. The nannoplankton bioevents are used instead of stage and epoch boundaries in plotting of the burial history models for the studied wells, which greatly improved the precision of the maturation onset and hydrocarbon generation. This collection of nannoplankton biochronology based applications is of large importance for the future petroleum exploration in the Nile Delta region.

Quantitative studies of the calcareous nannoplankton of Sarmatian deposits: case studies in the Sieniawa–Rudka area (Outer Carpathian Foredeep, Poland)

The aim of this study was the qualitative and quantitative analysis of the calcareous nannofossil assemblages of the Machow Formation, belonging to the supra-evaporitic complex of the Polish Carpathian Foredeep Basin (PCFB). The work was concentrated in the eastern part of the PCFB, in the Sieniawa–Rudka area (Ryszkowa Wola Horst). Samples were collected from the Rudka-13 and Wylewa-1 boreholes. On the basis of calcareous nannoplankton, these deposits were assigned to the upper part of the NN6 Zone combined with the NN7 Zone, which corresponds to the Sarmatian s.s. of the Central Paratethys (upper Serravallian of the Mediterranean scale). Conclusive determination of the biozone NN7 was problematic, owing to the absence of the rare zonal marker species Discoaster kugleri . The typical association of the undivided NN6–NN7 Zone was of low species diversity and usually dominated by Coccolithus pelagicus , C yclicargolithus floridanus and Reticulofenestra pseudoumbilica (> 7 µm). On the basis of the relative abundance of species, a significant amount of redeposition was deduced. The reworked nannofossils were mostly Eocene in age. The Oligocene, Early Miocene and Late Cretaceous species occurred much less frequently. The dominance of Eocene forms indicates the Carpathians as the main supply area. The Late Cretaceous taxa may have originated from the Senonian marly deposits of the Miechow Trough in the north. Statistical treatment of the quantitative data was performed using multivariate cluster analysis and Nonmetrical Multidimensional Scaling (nMDS). The composition of the calcareous nannofossil assemblages, together with the high percentage of allochthonous taxa, indicate a shallow, coastal environment with a high supply of nutrients.

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.

Easternmost Mediterranean evidence of the Zanclean flooding event and subsequent surface uplift: Adana Basin, southern Turkey

Abstract According to the literature, the Adana Basin, at the easternmost part of the Mediterranean Basin in southern Turkey, records the Pliocene stage with shallow-marine to fluvial deposits. Our micropalaeontological analysis of samples from the Adana Basin reveal Late Lago–Mare biofacies with Paratethyan ostracod assemblages pertaining to the Loxocorniculina djafarovi zone. Grey clays rich in planktonic foraminifera lie above the Lago–Mare deposits. Within the grey clays, the continuous occurrence of the calcareous nannofossil Reticulofenestra zancleana and the base of the Reticulofenestra pseudoumbilicus paracme points to an Early Zanclean age (5.332–5.199 Ma). Both ostracod and benthic foraminifera indicate epibathyal and bathyal environments. 87 Sr/ 86 Sr measurements on planktonic and benthic foraminifera fall below the mean global ocean value for the Early Zanclean, indicating potentially insufficient mixing of low 87 Sr/ 86 Sr Mediterranean brackish ‘Lago–Mare’ water with the global ocean in the earliest Pliocene. We utilize the ages and palaeodepths of the marine sediments together with their modern elevations to determine uplift rates of the Adana Basin of 0.06 to 0.13 mm a −1 since 5.2–5.3 Ma (total uplift of 350–650 m) from surface data, and 0.02–0.13 mm a −1 since c. 1.8 Ma (total uplift of 30–230 m) from subsurface data. Supplementary material: Microphotographs of foraminifers, ostracods, and calcareous nannofossils, plots of the calcareous nannofossil frequencies, occurrence of foraminifers and ostracods in the study sections, results of Sr isotopic analysis, and a complete list of fossils are available at www.geolsoc.org.uk/SUP18535 .

Biostratigraphic and palaeoenvironmental analyses of the Messinian/Zanclean boundary and Zanclean succession in the Moncucco quarry (Piedmont, northwestern Italy)

Abstract Integrated biostratigraphic and palaeoenvironmental analyses of foraminiferal, ostracod and calcareous nannofossil assemblages were carried out on the Messinian/Zanclean succession of the Moncucco quarry (Piedmont, northwestern Italy). The uppermost Messinian deposits may be correlated to the “Lago-Mare” deposits of the Mediterranean area. They yield a brackish ostracod assemblage, which belongs to the Loxocorniculina djafarovi zone of the Messinian post-evaporitic interval, indicating their deposition in oligo-mesohaline shallow waters and the influx of Paratethyan faunas. Only reworked marine microfossils are present. The boundary between the “Lago-Mare” deposits and the overlying Zanclean Argille Azzurre Fm. is marked by an irregular erosional surface, followed by a barren, 10–50 cm thick, black arenitic layer. The Zanclean succession consists of grey to whitish clayey marls (Argille Azzurre Fm.), rich in microfossils, which document the MPl1 (Sphaeroidinellopsis acme) zone up to the MPl4a foraminiferal zone, and the MNN12 to MNN14-15 calcareous nannofossil zones. Micropalaeontological data confirm that the Pliocene flooding event was synchronous at the Mediterranean scale. Some foraminiferal bioevents recognized at the Mediterranean scale and related to precessional cycles are recorded in the studied succession : the Globorotalia scitula common occurrence (CO) (cycle 3), the occurrence of Siphonina reticulata (cycle 6), and the Globorotalia margaritae first common occurrence (FCO) (cycle 10). A short hiatus could be inferred in the lowermost Zanclean sediments for the absence of Triquetrorhabdulus rugosus and of the Reticulofenestra pseudoumbilicus paracme. Hiatuses or reduced sedimentation could also have affected the bottom during the MPl2-MPl3 zones. Foraminiferal and ostracod assemblages document a rather deep basin just from the lower Zanclean, warm surficial waters (common Globigerinoides spp.), rather high seasonal primary productivity (common phytoplankton grazer Neogloboquadrina acostaensis) and mesotrophic bottom (common Eponides pusillus, Hoeglundina elegans, Argilloecia acuminata, Krithe compressa, Paijenborchella iocosa). Bottom depths in the lower Zanclean of northwestern Italy appear to be shallower than depths suggested by coeval southernmost assemblages. A deepening of the basin during the MPl1 and MPl2 zones is suggested by the increasing diversity of microfossils and by the spreading of deep bathyal taxa (Cibicidoides robertsonianus, Paijenborchella malaiensis cymbula). Warm, oligotrophic conditions in the water column become more constant. Palaeoenvironmental conditions change progressively during the upper MPl2, the MPl3 and MPl4a zones. Cold, eutrophic planktonic foraminifers (Globigerina bulloides, N. acostaensis) become dominant, as well as benthic taxa tolerant of low oxygen content and high organic matter (Uvigerina peregrina, Brizalina spp.), suggesting an increase in eutrophic conditions. Deep benthics such as Cibicidoides kullenbergi, C. robertsonianus disappear, and many outer neritic to bathyal taxa decrease in abundance, whereas inner shelf taxa increase, suggesting a shallowing of the basin and episodes of strong winnowing, probably tectonically controlled, in the uppermost Zanclean succession.

Age calibration of dinoflagellate cyst and acritarch events in the Pliocene–Pleistocene of the eastern North Atlantic (DSDP Hole 610A)

An independently calibrated record of dinoflagellate cyst and acritarch events is presented for the Early Pliocene through Middle Pleistocene (ca. 4.0–0.5 Ma) of eastern North Atlantic Deep Sea Drilling Project (DSDP) Hole 610A. A new age model is established for this hole and tied to marine isotope stratigraphy and magnetostratigraphy back to 3.6 Ma. New data on the range of the calcareous nannofossil Reticulofenestra pseudoumbilicus indicate that the base of this hole is about 1.0 Myr younger than previously thought. A diverse dinoflagellate cyst and acritarch record allows the significant highest and/or lowest occurrences of 19 dinoflagellate cyst and seven acritarch taxa to be recognised in Hole 610A and calibrated to the latest astronomically-tuned Neogene time scale (ATNTS 2004) via our new age model. Comparing records across the North Atlantic and Mediterranean reveals near-synchronous highest occurrences of the dinoflagellate cysts Ataxiodinium confusum (2.63–2.65 Ma), Invertocysta lacrymosa (2.72–2.74 Ma in the eastern and central North Atlantic and Mediterranean) and Impagidinium solidum (ca. 3.15–3.17 Ma), and the acritarch Leiosphaeridia rockhallensis (ca. 3.83–3.88 Ma). Highest occurrences of the dinoflagellate cyst Batiacasphaera minuta/micropapillata (3.83–ca. 3.7 Ma) and acritarch Cymatiosphaera latisepta (2.49–2.63 Ma) also provide useful markers for correlation. A precise stratigraphy for Hole 610A allows us to evaluate the impact of paleoceanographic and climatic events on the dinoflagellate cyst record. Climatic and oceanographic reorganizations associated with the onset of Northern Hemisphere glaciation appear responsible for the disappearance of many species between 2.8 and 2.6 Ma. The lowest occurrence of Impagidinium cantabrigiense (1.86 Ma) in the Olduvai Subchron is one of the few good biostratigraphic markers for the uppermost Gelasian in Hole 610A.

Surface water dynamics and phytoplankton communities during deposition of cyclic late Messinian sapropel sequences in the western Mediterranean

Distinctive precession-scale sapropel/marl sequences of late Messinian age are found in several outcrops bordering the western Mediterranean. To examine the roles of stratification and productivity in driving this cyclic sedimentation, we performed a high resolution analysis of calcareous nannofossil assemblages through four orbital sequences (composed of sapropel/marl/diatomite/marl) from the Sorbas basin in southern Spain. This effort also involved a detailed comparison between calcareous nannofossil abundances and other micropaleontological, sedimentological and geochemical proxies to further understand the behaviour of some taxa. For this period, fluctuations in the depth and gradient of the pycnocline, and the distribution and remobilization of nutrients seem to be the main factors controlling the calcareous nannoplankton assemblages, with temperature of secondary importance. In the sapropels, the warm-oligotrophic genus Sphenolithus and Discoaster are abundant. Especially significant is the progressive increase towards the top of Discoaster pentaradiatus, indicator of severe oligotrophic (deep pycnocline) conditions. At the top of the sapropels, peaks in Reticulofenestra rotaria are interpreted here as the result of an increase of surface water temperatures, although decreasing salinity may also play a role. Small Reticulofenestra (< 5 μm) is the major component of the overlying marl, and peaks in episodes of high nutrient availability (assessed here by the phosphorus proxy P/Ti). This morphotype is linked to a relatively shallow deep chlorophyll maximum, with a stable but shallow thermocline. Overlying the marl is a diatomite bed, interpreted here as an indicator of peak nutrient availability (confirmed by P / Ti ratios), with a reduction of calcareous nannofossils due to nutrient competition and dilution. Interestingly, however, species such as Reticulofenestra pseudoumbilicus (> 5 μm) are more frequent in diatomites even considering conditions of extreme mixing and eutrophication occurred in the basin. Umbilicosphaera jafari peaks just after diatomites, replacing small Reticulofenestra, probably as a response to an increase in salinity and/or nutrient limitation. Species such as Coccolithus pelagicus and Helicosphaera carteri are abundant at the top of the diatomites and in the overlying marls, indicating relatively mesotrophic and cool water conditions. This succession shows similar characteristics in the four studied cycles, allowing us to interpret surface water dynamics in this region on orbital time scales. The top of the sapropel represents a warm, low salinity and well stratified episode under a situation of maximum insolation. A well developed pycnocline and oligotrophic conditions (moderate production of calcareous phytoplankton) coinciding with anoxic conditions at the bottom enhance the preservation of organic matter, and consequently generate a sapropel. Diatomites are deposited under a situation of unstable pycnocline that produce an increase in productivity in surface waters. Diatoms significantly deplete limiting nutrients, and consequently calcareous nannofossils start to be dominant again in the water column as result of a progressive stabilization of the pycnocline.

Nannofossil evolutionary events in the mid-Pliocene: an assessment of the degree of synchrony in the extinctions of Reticulofenestra pseudoumbilicus and Sphenolithus abies

The mid-Pliocene was an interval of subtle reorganisation within the nannoplankton community, including the prominent and biostratigraphically important last occurrences of Sphenolithus abies and Reticulofenestra pseudoumbilicus. The transition is part of the Pliocene to Recent ‘attrition’ of nannofossil species that resulted from changes in the distribution of trophic resources, and deep-water and surface-water current systems, likely associated with the initiation of Northern Hemisphere glaciation. The extinctions of Sphenolithus abies and Reticulofenestra pseudoumbilicus were analysed in detail at ODP Sites 659, 662, and 926 in the equatorial and subequatorial Atlantic. These taxa show significantly different patterns of duration and timing of decline based on high-resolution abundance records and calibration with oxygen isotope stratigraphy. The initiation of abundance decline between 3.71 and 3.67 Ma and the extinction of S. abies between 3.56 and 3.52 Ma are diachronous. This extinction may have been a response to the intensification of glacial intervals at this time. In contrast, the last occurrence of R. pseudoumbilicus at 3.81–3.82 Ma appears to be a valid example of biostratigraphic (although not necessarily biological) synchrony in the fossil record. Direct environmental forcing is not attributable for the extinction of R. pseudoumbilicus; however, indirect physical and/or biological environmental stress may explain the observed patterns.

CALCAREOUS PLANKTON HIGH RESOLUTION BIOSTRATIGRAPHY (FORAMINIFERA AND NANNOFOSSILS) OF THE UPPERMOST LANGHIAN – LOWER SERRAVALLIANRAS IL-PELLEGRIN SECTION (MALTA)

Results of an integrated biostratigraphic (calcareous nannofossils and planktonic foraminifers) study of the uppermost Langhian/lower Serravallian Ras il-Pellegrin section (Fomm ir-Rih Bay – Malta) are presented. This high resolution study allowed us to recognise several useful lower Serravallian bio-events in the Mediterranean and to provide a detailed distribution pattern of the recognised taxa. The astrochronological calibration, reported in a different paper of this volume, provided absolute ages of the bio-events of the studied section. The LO (Last Occurrence) of Globorotalia peripheroronda at 13.39 Ma, the Paragloborotalia partimlabiata FO (First Occurrence) at 12.62 Ma and the Paragloborotalia mayeri FCO (First Common Occurrence) at 12.34 Ma among the planktonic foraminifera, and the Sphenolithus heteromorphus LO at 13.59 Ma, the Cyclicargolithus floridanus LCO (Last Common Occurrence) at 13.39 Ma, the Reticulofenestra pseudoumbilicus FCO at 13.32 Ma, the Calcidiscus macintyrei FO at 12.57 Ma and the Calcidiscus premacintyrei LCO at 12.51 Ma among the calcareous nannofossils, were recorded. Moreover, our results confirm the LO of S. heteromorphus as a fairly synchronous event in the Mediterranean and in the Atlantic and Pacific Oceans. Therefore, we suggest a lithological level near or coincident with this event for the definition of the GSSP of the Serravallian. The Ras il-Pellegrin section may be considered a good candidate for this definition.