Globorotalia Puncticulata Research Articles

Biostratigraphical and paleoenvironmental studies of some Miocene‒Pliocene successions in Northwestern Nile Delta, Egypt

ABSTRACT Cuttings and logs from four boreholes in the Mediterranean Sea, offshore the northwestern side of the Nile Delta, Egypt (30°00’–30°24’ N, 31°18’–31°30’ E), were examined lithostratigraphically, biostratigraphically and paleoenvironmentally. Five planktonic foraminiferal zones were determined assigning the studied boreholes to be late Miocene-Early Pliocene in age. These zones are Globorotalia mediteraneaneana Zone Sphaeroidinellopsis seminulina Zone, Globorotalia margaritae margaritae Zone, Globorotalia puncticulata Zone and Globorotalia inflate. Studying benthonic foraminifera indicated a general shallowing upward trend in all boreholes and tracking the distribution of the foraminiferal assemblages by counting the total number of foraminifera and planktic/benthic ratios provide a history of the progression of deltaic facies with secondary cycles of sea-level change.

NEW' DATA ON PLANKTONIC FORAMINIFERA BIOSTRATIGRAPHY FROM THE NEOGENE OF THE GARGANO PENINSULA (FOGGIA, SOUTHERN ITALY)

This paper concerns detailed analyses on planktonic foraminifera biostratigraphy of a section outcropping in the area of Poggio Imperiale, the western side of Gargano (FG)
 The sediments overlying the mesozoic carbonate platform have been assigned to Globorotalia puncticulata Zone (Early Pliocene) and to Globorotalia inflata Zone (Late Pliocene). A Middle Pliocene stratigraphic gap has been recognised.

Manual of Neogene foraminifera from off-shore Nile Delta (Egypt) and their biostratigraphic significance

The Mediterranean Nile Delta is a major target for hydrocarbon reservoirs. In the search for hydrocarbons, high-resolution biostratigraphy has long been established as high-impact and low-cost solution to face the challenges in the move towards structurally more complex and unexplored areas. To date, the biozonation of the Nile Delta is largely provided by benthic and planktonic index foraminifera. We have examined the foraminifera assemblages from NDOB-1, a borehole in the northern part of the Nile Delta. The material recovered provides unique and exceptionally well-preserved microfossil biotas that completely cover the Neogene succession (Middle Miocene to Pleistocene). This allows the establishment of an intact biozonation scheme for the Nile Delta region with reliable chronostratigraphic correlation and suitable industrial applications.The stratigraphic succession of the Nile Delta region consists of seven formations: Sidi Salim Formation, Qawasim Formation, Rosetta Formations, Abu Madi Formation, Kafr El Sheikh Formation, El Wastani Formation and Mit Ghamr Formation. Examination of the planktonic foraminifera assemblages of the NDOB-1 borehole from the deep part of the Nile Delta lead to the identification of twelve biozones: Globorotalia inflata Interval Zone, Globorotalia aemiliana Interval Zone, Globorotalia puncticulata Interval Zone, Globorotalia puncticulata- Globorotalia margaritae Concurrent Range Zone, Globorotalia margaritae Interval Zone, Sphaeroidinellopsis seminulina Acme Zone, Non-distinctive Zone, Globorotalia suterae Interval Zone, Globigerina woodi Interval Zone, Globorotalia mayeri Interval Zone, Globorotalia fohsi peripheroronda Interval Zone and Praeorbulina glomerosa Interval Zone. The biozones fully cover the time span from the Middle Miocene to the Pleistocene. The benthic foraminifera recovered allow the identification of five benthic biozones for the Pliocene and Pleistocene: Hyalinea balthica Interval Zone, Bulimina marginata Interval Zone, Bulimina aculeata Interval Zone, Gyroidinoides laevigata Interval Zone and Uvigerina rutila Interval Zone. The identified planktonic bioevents were used to calibrate the studied Neogene section with the Astronomically Tuned Neogene Time Scale (ATNTS, 2012).

Depositional environment and age of some key Late Pliocene to Early Quaternary deposits on the underfilled Cedrino paleovalley (Orosei): Insight into the Neogene geodynamic evolution of Sardinia

In order to better constrain the relationship between tectonics and sedimentation of the Eastern Sardinian Margin, from the Messinian to the present day (METYSS project), a lithostratigraphic study was carried out on the Late Neogene deposits along the Cedrino Valley (eastern Sardinia). The late Neogene evolution is documented from sedimentological and tectonic analysis, biostratigraphic dating, and by mapping and logging stratigraphic sections. Previous authors have differentiated an early Pliocene marine formation from an older continental formation, possibly Miocene, the entire system being covered by late Pliocene to Quaternary lava flows. Preliminary biostratigraphic data suggest the absence of the lowermost Pliocene, based on the absence of Globorotalia margaritae and the presence of Globorotalia puncticulata, implying a sediment age between 3.81 and 2.41 Ma. At the foot of the Fiuli cliff, some mud clasts include a coccolith microflora, Tortonian in age, suggesting reworking. The Pliocene marine deposits consist of a single filling sequence instead of a succession of superimposed sequences as we would expect during this period of time; the occurrences of terms rarely respect the usual transgressive-regressive succession. Contrasting bathymetric environments (fore-shore, pro-delta, shelf or upper slope) can be abruptly superimposed on top of the other, along few meter thick intervals. A rapidly flooded term is observed in several sites and indicates a spatial variability over only a few kilometers distance. Some deep water deposits are in the middle of the infilling Pliocene sequence, whereas shallower water deposits can be repeated along a vertical section, or even interrupted by emersion. These marked differences can express syn-, or possibly post-sedimentation tectonic uplifts. The 10–25° bed dips originated through local tectonic uplift. At Fiuli, the geometry of the bedding planes is indicative of tilting toward the west, in a direction opposite to the one observed at Onifai. These Pliocene series form a wide syncline with an approximately NNE–SSW axis. This morpho-structural behavior appears to be largely atypical of this East-Sardinian coastal area.

The response of calcifying plankton to climate change in the Pliocene

Abstract. As a result of anthropogenic pCO2 increases, future oceans are growing warmer and lower in pH and oxygen, conditions that are likely to impact planktic communities. Past intervals of elevated and changing pCO2 and temperatures can offer a glimpse into the response of marine calcifying plankton to changes in surface oceans under conditions similar to those projected for the future. Here we present new records of planktic foraminiferal and coccolith calcification (weight and size) from Deep Sea Drilling Project Site 607 (mid-North Atlantic) and Ocean Drilling Program Site 999 (Caribbean Sea) from the Pliocene, the last time that pCO2 was similar to today, and extending through a global cooling event into the intensification of Northern Hemisphere glaciation (3.3 to 2.6 million years ago). Test weights of both surface-dwelling Foraminifera Globigerina bulloides and thermocline-dwelling Foraminifera Globorotalia puncticulata vary with a potential link to regional temperature variation in the North Atlantic, whereas in the tropics Globigerinoides ruber test weight remains stable. In contrast, reticulofenestrid coccoliths show a narrowing size range and a decline in the largest lith diameters over this interval. Our results suggest no major changes in plankton calcite production during the high pCO2 Pliocene or during the transition into an icehouse world.

A major change in the sedimentation regime in the Crotone Basin (Southern Italy) around 3.7–3.6 Ma

The Lower Pliocene succession of the Crotone Basin (Calabrian Arc, Southern Italy) is mainly comprised of blue-grey marly clay with good magnetic properties. Here the bio-magnetostratigraphic data indicate a mean sedimentation rate of about 12–15cm/kyr. Around 3.7–3.6Ma a major change in the sedimentation regime occurred: the blue-grey hemipelagic marls grade rapidly into silty marls with a significant increase in the terrigenous fraction and with abundant siliceous remains throughout the whole interval. Magnetic properties of these sediments are very poor, but an integrated calcareous plankton biostratigraphy (foraminifera and nannofossils) infers a high average sedimentation rate (about 50–60cm/kyr). The abrupt onset of this sedimentation regime in the Crotone Basin is contemporaneous with a major unconformity already recognized in the northern sector of the basin, part of a major reorganization phase in the whole Apenninic–Maghrebid Chain known as “Globorotalia puncticulata event”. Reports of coeval siliceous sediments in other marginal basins of the Apennines (Southern Calabria, Southern and Northern Apennines) suggest that this “siliceous event” might have been regionally extensive, having important palaeoceanographical implications. We infer that the “siliceous event” is characterized by a combined tectonic- and climate-induced change in palaeoceanographic conditions. The tectonic triggering factors may have been linked to two synchronous events in the Tyrrhenian–Apennine system: 1) the shortening event also known as “G. puncticulata event”, and 2) the coeval opening of the Vavilov Basin in the Tyrrhenian Sea which yielded profound influences in terms of physiography and characteristics of the Crotone Basin. The consequent uplift of the Southern Apennines would have increased sediment supply and availability of silica, resulting in eutrophication and enhanced silica preservation. Strong winter mixing and possibly upwelling conditions could have increased primary productivity during heavy isotope stages Gi4, Gi2 and MG8, at the onset of the “siliceous event”. This important event, lasting from ca. 3.6Ma to ca. 3.2Ma, would have recorded a peculiar transitional period before further climatic deterioration and more drastic palaeoceanographic changes occurred around 3.1Ma, leading to cyclic sapropel deposition in the whole of the Mediterranean sea.

Evidence for an Early-Middle Miocene age of the Navidad Formation (central Chile): Paleontological, paleoclimatic and tectonic implications

* Corresponding author ABSTRACT. The age of the Navidad Formation in central Chile has always been controversial, mainly due to the conflicting age ranges indicated by its macro- and microfossils. Macrofossils are generally interpreted as having been reworked from older, Early to Middle Miocene strata, whereas a Late Miocene-Pliocene age has been accepted on the basis of planktonic foraminifer index species. The results of this study, however, indicate that the macrofossils occur in situ, which necessitates a complete revision of the geochronological data. It is concluded that the evidence for an Early to Middle Miocene age is overwhelming, and that the planktonic foraminifer index species must have appeared in the SE Pacific earlier than elsewhere. These include Globoturborotalia apertura, Globorotalia puncticulata (Deshayes), Globorotalia spheriomizea (Walters), Neogloboquadrina pachyderma (Ehrenberg), and Neogloboquadrina acostaensis (Blow). An Early to Middle Miocene age for the Navidad Formation correlates well with a reinterpretation of its depo- sitional environment as a continental shelf instead of a deepwater continental slope, global and regional paleoclimatic events, and the tectonic development of the Andes Range.

Foraminiferal biostratigraphy of the Pliocene–Pleistocene deep marine offshore, north Nile Delta, Egypt

A high resolution biostratigraphic analysis of the Pliocene–Pleistocene sequence of the offshore Nile Delta region in West Delta Deep Marine Concession (WDDM), in which 29 planktonic foraminiferal species belonging to 8 genera and 51 benthic foraminiferal species belonging to 40 genera were identified, allowed the recognition of seven foraminiferal zones and two subzones. These are as follows: Sphaeroidinellopsis Acme Zone (MPl1), Globorotalia margaritae Zone (MPl2), Globorotalia puncticulata / Globorotalia margaritae Zone (MPl3), Sphaeroidinellopsis s.l. Zone (MPl4), Globorotalia puncticulata Subzone (MPl4a), Globorotalia planispira Subzone (MPl4b), Globigerinoides elongatus Zone (MPl5), Globorotalia inflata Zone (MPl6) and Hyalinea balthica Zone.

Geologia dell’area di Rapolano Terme in Provincia di Siena (Appennino Settentrionale)

Geologia dell’area di Rapolano Terme in Provincia di Siena (Appennino Settentrionale)

Globorotalia puncticulata: Population divergence, dispersal and extinction related to Pliocene–Quaternary water masses

The isolating effect of water mass partitioning of populations on the morphology, stratigraphic distribution and extinction of planktonic foraminifera is assessed from the Pliocene–Quaternary record of Globorotalia puncticulata. Southern Hemisphere, Mediterranean and North Atlantic data on these aspects of its history are examined and appear consistent with a limited dispersal biogeographic model wherein populations are largely confined by hydrographic barriers. Earliest populations appeared during the latest Miocene in Southern Hemisphere middle latitude water masses. However, morphometric analysis shows that significant differentiation in the axial shape of shells had developed by 4 Ma between Southwest Pacific populations from ODP Site 1123 (temperate water) and ODP Site 1119 (subantarctic water). These sites are in close proximity but separated by the Subtropical Front. At Site 1123 inflation of late-formed chambers and reduction in the number included in the outer whorl created shell profiles that anticipated the globose form of Globorotalia inflata. The latter's gradual evolution from G. puncticulata s.s. took place in this temperate water mass, with the earliest morphotypes with three chambers in the outer whorl present by 4.1 Ma. In contrast, subantarctic populations at Site 1119 retained four chambers but their axial shape was modified. The development of a large, highly arched aperture and increase in the number of chambers in the outer whorl in Mediterranean–North Atlantic Globorotalia puncticulata bononiensis is an example of population differentiation later in the Pliocene. Chronostratigraphy shows that the northward expansion of central temperate water populations commenced with their occupation of Southwest Pacific subtropical water about 4.8 Ma. The rather abrupt entry of substantial populations into Mediterranean and North Atlantic water at 4.5 Ma marked a major biogeographic expansion and established G. puncticulata as a bipolar species. It was widely distributed about 3 Ma, with major populations in several water masses during a period of middle Pliocene warmth. After this acme North Atlantic and Mediterranean G. puncticulata bononiensis populations collapsed as late Pliocene Northern Hemisphere glacials intensified. They were extinguished in MIS 96 (2.4 Ma). Concurrently, G. puncticulata s.s became extinct in the warm subtropical Southwest Pacific. Subantarctic populations persisted but in turn were decimated in severe glacials during the Middle Pleistocene Transition. Most had disappeared by MIS 16 (0.66 Ma). However, at Sites 594 and 1119 there was a small Lazarus-like revival in MIS 11 (0.41 Ma). The highest known occurrence is in MIS 9 (0.33 Ma) at Site 1119. Confinement of the species to subantarctic water in the Pleistocene may have raised its vulnerability to extinction. While stable isotope data indicate that the lineage's evolution is related to depth habitat selection about the thermocline, its biogeography suggests that hydrographic barriers significantly isolated populations and probably facilitated speciation. Eddies such as the North Brazil Current rings provide conduits for inter-water mass transfer of populations but the history of G. puncticulata suggests that such mechanisms seldom operated successfully. The morphology of the lectotype of G. puncticulata s.s., from beach sand at Rimini, Italy, is consistent with a lower Pliocene source. Reports of living occurrences are poorly documented and the species is considered to be extinct.

Identification des zones biostratigraphiques méditerranéennes dans le Pliocène du Cap-Bon (Tunisie)

The Nabeul-Hammamet series analysis allows to recognize the six biozona known in the Mediterranean realm, as specified by Cita (1975a). These are: the Sphaeroidinellopsis subdehiscens BANNER & BLOW acme biozone equivalent to MPL1; the Globorotalia margaritae margaritae BOLLI & BERMUDEZ interval zone (= MPL2); the Globorotalia margaritae BOLLI & BERMUDEZ , Globorotalia puncticulata (DESHAYES), concurrent range zone (= MPL3); the Sphaeroidinellopsis subdehiscens BANNER & BLOW interval zone (= MPL4); the Globigerinoides elongatus (D’ORBIGNY) interval zone (= MPL5); the Globorotalia inflata (D’ORBIGNY) interval zone (= MPL6). There is no similarity between these biozones and those established by Berggren and al. (1995) for the atlantic and the indo-pacific realms. The MPL1, MPL2, MPL3 and MPL4 zones are especially englobed in argillaceous and yellow sandy lithological units specified in north-eastern Tunisia, such as ‘Argiles des Potiers’, ‘Sables Jaunes de Nabeul’ and ‘Argiles de Sidi Barka’. These units are together equivalent to the Raf-Raf Formation developed towards the North, in the Bizerte area. Besides, the MPL5 and the MPL6 zones are included in sands and sandstones composing the Hammamet unit, equivalent to the Porto-Farina Formation.

Paleoecology, stratigraphy and taxonomy of the pliocene marine diatoms from central crete (Greece)

A rich siliceous phytoplankton assemblage of late Early Pliocene to early Late Pliocene age, containing 31 genera of marine diatoms with 55 specific taxa, was found in fine laminated diatomite beds in the sections of Kallithea, Marathitis, Prassas and Aitania from the northern central part of the Crete Island (Province of Heraklion, Greece). The sediments of the studied sections belong to the upper part of the Stavromenos facies-unit (Early to Late Pliocene). The diatom associations were mainly investigated for their paleoecology, stratigraphy and taxonomy. The diatom assemblages are characterized by species typical of low latitudes. They belong to the upper part of the Nitzschia jouseae biozone (Early Pliocene — Late Pliocene) because of the presence of the marker species N. jouseae, which is rare to frequent in the Kallithea and the Marathitis sections, and rare in the Prassas and Aitania sections. The upper part of the N. jouseae biozone corresponds to the CN11b ( Discoaster asymmetricus) and CN12a ( D. tamalis) subzones of calcareous nannofossils as well as to the Globorotalia puncticulata and Gl. bononiensis biozones of planktic foraminifera. Among the diatoms the planktie, centrie species dominate in terms of their percentage distribution and reflect a succession of two paleoclimate intervals : a subtropical interval with the warm-water species Azpeitia nodulifer, Hemidiscus cuneiformis and Thalassiosira leptopus and a temperate interval characterized by the cold-water species Coscinodiscus marginatus. These two intervals are proposed as two new local acme subzones.

The significance of Messinian occurrences of Globorotalia margaritae and Globorotalia puncticulata in Sicily

ABSTRACT Globorotalia puncticulata and Globorotalia margaritae are critical species that define internationally recognized planktonic foraminiferal biozones in the Pliocene. These biozones are defined from stratotype sections on Sicily and their fauna are commonly considered to have been introduced to the Mediterranean after an influx of Atlantic water that terminated the late Miocene desiccation of the basin. Herein new discoveries of these species in rocks that predate the late Miocene desiccation are described. These data are supported by magneto‐ and lithostratigraphy that have been integrated at a single continuous section. Not only do these discoveries question the existing foraminiferal biozone stratigraphy, they also suggest new models for the dispersal of planktonic species. It is proposed that Globorotalia puncticulata and perhaps even Globorotalia margaritae evolved in the Mediterranean during earliest Messinian times (during or before chron C3Bn1n) and dispersed into the Atlantic. This suggests that a marine connection remained between the two sea areas until at least chron C3An.1n. Using the existing geomagnetic polarity time scale, these occurrences are some 2 Myr earlier than previously recorded in the Mediterranean. The distribution of G. margaritae and G. puncticulata in Mediterranean sections is likely to reflect palaeoenvironment or the preservation of deposits rather than the absolute age of the sediments.

The formation of Pliocene sapropels and carbonate cycles in the Mediterranean: Diagenesis, dilution, and productivity

High‐resolution micropaleontological (planktonic foraminifera and calcareous nannofossils) and geochemical (stable isotopes, organic carbon, Fe, P, S, Ca, Ba, Mn, and Al) records are presented for the first sapropel‐containing carbonate cycle in the Pliocene of Sicily. The carbonate cycle is characterized by a gray to white to beige to white color layering typical of the marls of the Trubi formation. A faintly laminated sapropel is intercalated in the gray‐colored bed of the carbonate cycle. CaCO3 content varies from 40% in the beige to 45‐50% in the white layers. Lowest CaCO3 content of 25–30% is found in the gray layer and sapropel. Variations in carbonate and organic matter percentages can best be explained by changes in paleoproductivity rather than by variations in dilution and dissolution. Total productivity was highest during deposition of the gray layer and sapropel, as indicated by high organic carbon and Ba contents and high abundance of Globorotalia puncticulata. Carbonate production reached its highest values, however, during deposition of the white layers, as evidenced by enhanced abundances of planktonic foraminifera and nannofossils. The low carbonate content in the gray layer and sapropel is explained in terms of a collapse in carbonate production caused by extreme changes in the physical and biochemical properties of the water column, which in turn resulted in siliceous plankton and opportunistic foraminifers such as Globorotalia puncticulata outcompeting most calcareous organisms. The beige layer represents a low‐productivity environment similar to the present‐day eastern Mediterranean basin. Several mechanisms have previously been proposed to explain variations in productivity in the eastern Mediterranean. Both sapropels and gray layers were deposited at times when perihelion occurred in northern hemisphere summer. We envisage that the increase in seasonal contrast resulting from this orbital configuration enhanced winter mixing and stabilization of the water column during summer, both leading to favorable conditions for intensification of the spring bloom. In addition, a decrease in excess evaporation, as can be deduced from the δ18O record, led to shoaling of the pycnocline and reduced circulation, thus enhancing the availability of nutrients in the photic zone. Finally, enhanced precipitation and associated runoff should have caused an increase in river‐borne nutrients.

Magnetostratigraphy of Pliocene Sediments From the Stirone River (Po Valley)

The Miocene-Pliocene and Pliocene-Pleistocene boundaries bracket a Pliocene section, approximately 800 m thick, along the Stirone river near Parma (Northern Italy). From the base to the top, the sequence consists mainly of blue clays (Zanclean in age), whitish laminates, silty clays and sandstones of Piacenzian age. A debris flow, which is the sedimentary expression of a hiatus, separates the Zanclean from the Piacenzian sediments. Thermomagnetic analysis, thermal evolution of magnetic susceptibility, acquisition and removal of anhysteretic and isothermal remanent magnetization (ARM and IRM) by alternating field and thermal methods, X-ray diffraction and scanning electron-microscopy (SEM) have been used in conjunction to try and unravel the complex magnetic mineralogy of the Stirone samples. Two major carriers of the magnetic remanence appear to be pseudo-single domain (PSD) magnetite and high-coercivity pyrrhotite in varying amounts and grain sizes. Five different magnetic indicators yield roughly consistent logs, with magnetite being important in the lower part of the section and pyrrhotite becoming dominant upsection. Six zones with more or less uniform properties have been outlined. Except in the lowermost zone where magnetite is also an important carrier, pyrrhotite in the 150-350°C range is taken to be the main carrier of the characteristic and, we believe, primary magnetization. The overall mean direction for about 200 samples is D = 0, I = 52 (ag5 = 3), corresponding to a lack of local rotation about a vertical axis but implying some 10 of inclination shallowing. The magnetostratigraphy encompasses ten successive polarity zones. Correlation of magnetic and biostratigraphic results to the geomagnetic polarity time scale and to the biozonation of the Mediterranean area leads to the proposal that the Thvera subchron and part of the above reversed polarity zone are missing, as revealed by the absence of the Sphaeroidinellopsis seminulina s.1. Zone and by the occurence of Globorotalia margaritae from the very base of the section. The Sidufjall and Nunivak subchrons are recognized and the first occurrence of Globorotalia puncticulata occurs just above Nunivak subchron. The Cochiti subchron is observed next. A remarkable hiatus involves the upper part of the Gilbert chron up to the lower part of the Kaena subchron based on the record of the last occurrence of G. margaritae and G. puncticulata and the first occurence of G. aemiliana and G. bononiemis. Another hiatus involving the Reunion and Olduvai subchrons is suggested to occur in the upper part of the Pliocene sequence based on the absence of the G. inflata Zone and on the first occurrence of'Artica islandica, which marks the Pliocene/Pleistocene boundary, towards the top of the section. The average sedimentation rate is estimated to be 450-500 m Ma-' for the early Pliocene and 200-300 m Ma-1 for the late Pliocene. Despite highly non-uniform sedimentation, both reflecting the episodic nature of coupled tectonic and sedimentary processes on 359 Downloaded from https

Early Late Pliocene biochronology and surface water temperature variations in the Mediterranean

A high-resolution magnetobiostratigraphy is presented for the early Late Pliocene in Sicily. Paleomagnetic measurements on samples from 100 stratigraphic levels provide an unprecedented high-quality polarity sequence which extends from the upper reversed Gilbert to the upper normal Gauss subchron. The resultant chronology for the early Late Pliocene provides ages for the following principal Mediterranean bioevents: (1) FOD Globorotalia crassaformis at 3.40 Ma (2) prolonged absence of Globorotalia puncticulata between 3.38 and 3.16 Ma (3) LOD Uvigerina rutila at 3.16 Ma (4) LOD Sphaeroidinellopsis seminulina at 3.07 Ma (5) LOD Globoquadrina altispira at 3.04 Ma (6) LOD Cibicides italicus at 2.96 Ma. Summer and winter surface water temperature estimates for the period 3.50 to 2.92 Ma are based on the abundances of Globigerinoides sacculifer and Globorotalia puncticulata in 111 samples with an average resolution of some 5000 years. Short-term variations in temperature of the surface water and in colour and carbonate content of the sediment are primarily controlled by the equinoxal precession. A higher seasonality during deposition of the grey-coloured, carbonate-poor facies suggests that at that time the summer solstice occurred near perihelion, whereas an inverse alignment occurred at the time of deposition of white-coloured, carbonate-rich layers. This phase-relationship between the precession cycle and grey-coloured layers is also valid for the sapropels which began to intercalate in the grey-coloured layers at 2.94 Ma. Long-term changes in surface water temperatures include a warming between 3.38 and 3.18 Ma followed by a cooling from 3.18 to 3.03 Ma. The warming of Mediterranean surface waters at 3.38 Ma is believed to be associated with the final closure of the Isthmus of Panama. Consequent strengthening of the Gulf Stream injected larger volumes of warm surface water into the North Atlantic Drift and eastern boundary current and this caused surface water temperatures in the mid to high-latitude northeast Atlantic and Mediterranean to rise. The subsequent climatic cooling at 3.18 Ma is linked to a first stage of Northern Hemisphere continental ice growth.

Improved Dating of the Pliocene of the Eastern South Atlantic Using Graphic Correlation: Implications for Paleobiogeography and Paleoceanography

Graphic correlation of foraminifer and nannofossil events establishes a high resolution chronology for the Pliocene at Deep Sea Drilling Project Site 532. Coarsely sampled magnetic inclination data are reinterpreted to indicate a complete Pliocene section. The age model suggests mean accumulation rates of 9.5 cm 10-3 yr for the first half of the early Pliocene and 5.8 cm 10-3 yr throughout the later part of the early Pliocene early Pleistocene. Major upwelling began at the location of Site 532 at 3.2 Ma. Time series analysis indicated a 41 ky cyclicity to the CaCO3 record between 2 and 4.5 Ma. Data support ages of 1.9 Ma for the first appearance of Globorotalia truncatulinoides and approximately isochronous southern hemisphere first appearances for Globorotalia crassaformis (4.70 Ma), Globorotalia puncticulata (4.77 Ma), and Globorotalia inflata (3.68 Ma).

Determinación del límite Mioceno-Plioceno y reconocimiento del Plioceno Inferior en Tomares (Sevilla)

Planktonic foraminifera from 53 samples coming from Tomares (El Aljarafe, Sevilla) were investigated, allowing the identification of three biozones: GloborotaJul margaritse-Globoquadrina dehiscens Zone, Globorotalia puncticuJats s.l. Zone and Globorotalia crassaiormis Zone. The first one is assigned to the Upper Messinian and otbers to tbe Zanclian. The first evolutionary appearance of Globorotalia puncticulata sphericomiozea is virtually syncbronous with the extinction of Globoquadrina debiscens and the last event may serve as useful criteria in determining the position of the Miocene-Pliocene boundary.

Planktonic foraminifera from the Pliocene Coralline Crag of Suffolk, Eastern England

Abstract. Nine species of planktonic foraminifera have recently been identified from the Coralline Crag of Suffolk, Eastern England. Stratigraphically important species include Globorotalia puncticulata (Deshayes) and Neogloboquadrina atlantica (Berggren) whose joint ranges, based on evidence from the North Atlantic, indicate an age for the deposit of between c. 4.2 and 2.3 Ma; other published evidence suggests that it may not be younger than c. 3.4 Ma. The low planktonic foraminiferal species diversity is interpreted as being due to a combination of factors, including the shallow water nature of the Coralline Crag, which would preclude deeper water species of planktonic foraminifera, and the possibility that the source of the fauna was from relatively high latitudes of the North Atlantic via the northern entrance to the North Sea. The planktonic foraminifera recorded indicate that the water temperature of the sea was within the range 10–18°C.The Coralline Crag contains very rich Lusitanian faunas of gastropod and bivalve molluscs, bryozoans, ostracods and benthic foraminifera.

Miocene/Pliocene boundary magnetostratigraphy at Capo Sopartivento, Calabria, Itlay

A magnetostratigraphic study at Capo Spartivento (Calabria, southern Italy) indicates that the Miocene/Pliocene boundary lies in the lowest reversed interval (Chron 3r) of the Gilbert Chron. The magnetostratigraphic time frame gives an estimate close to 19 ka for the duration of individual limestone-marl couplets that characterize the lithology. The eight couplets within Chron 3r indicate that the age of the Miocene/Pliocene boundary is about 154 ka older than the age of the reversal at the top of Chron 3r (4.78 Ma). We therefore estimate the age of this boundary as 4.93 Ma, which is 420 ka younger than that given by Berggren et al. and 100 ka older than that given by Zijderveld et al. The first-appearance datums of Globorotalia margaritae and Globorotalia puncticulata are similarly estimated to have ages of 4.66 and 4.15 Ma, respectively, the former being considerably younger than its first appearance in the open ocean.