North Atlantic (Rockall Plateau) coccolith assemblage data for MIS 5 of ODP Hole 162-980B

Calcareous nannoplankton analyses on late quaternary sediments from the eastern North Atlantic ODP Site 980 (55°29'N, 14°42'W) provide detailed insight into palaeoceanographic and palaeoclimatic changes that occurred throughout the Termination II and the adjacent interglacial of the Marine Isotope Stage (MIS) 5. This study presents the development of the coccolith assemblage throughout the interglacial MIS 5 towards the beginning of the glacial MIS 4 in the vicinity of the Rockall Plateau and investigates and characterises the impact of climatic and environmental variations on the coccolith assemblage distribution between 135 and 65 ky. In general, the coccolith assemblage is dominated by Gephyrocapsa muellerae and Emiliania huxleyi, whilst significant changes in palaeoceanographic and palaeoclimatic conditions are mainly shown by variations of subordinate species. A drastic increase in coccolith accumulation rates and a change from a less to a higher diverse species assemblage indicate a rapid increase in surface water temperatures during the onset of MIS 5 from c. 127.5 ky on. Highest coccolith numbers, high numbers of taxa and a large diversity indicate highest coccolithophore primary productivity and peak interglacial conditions during MIS 5.5, which are due to the high influence of relatively warm surface water to this region. Coccolith numbers peak again around 120 ky and decline afterwards but stay above glacial levels. The two cooling events of MIS 5.4 and 5.2 interrupt the generally warm conditions and are indicated by lowered coccolith numbers, a drop of thermophile species and a reduction of the species diversity. Decreasing coccolith numbers and a slightly reduced diversity indicate that environmental conditions deteriorated towards the onset of MIS 4. The analysis of the coccolith assemblage reveals that not only the stadial events MIS 5.4 and 5.2 are characterised by colder conditions, but furthermore confirms the upcoming notion that MIS 5.5 was terminated by a slight short-term cooling of the surface water which occurred around 124 ky.

Stratigraphic update of the Cenozoic Sub-Numidian formations of the Tunisian Tell (North Africa): Tectonic/sedimentary evolution and correlations along the Maghrebian Chain

The Sub-Numidian Tertiary stratigraphic record of the Tunisian Tell has been updated by means of 11 stratigraphic successions belonging to the Maghrebian Flysch Basin (N-African Margin) reconstructed in the Tunisian Numidian Zone and the Triassic Dome Zone. The Sub-Numidian successions studied range from the Paleocene to the Priabonian, representing a major change in the sedimentation from the latest Cretaceous onwards. The Sub-Numidian succession and the Numidian Formation are separated by an Intermediate interval located between two erosive surfaces (local paraconformities). The stratigraphic analysis has revealed diachronous contacts between distal slope to basinal sedimentary formation, allowing the identification of an Early Eocene Chouabine marker bed. The integrated biostratigraphic analysis made by means of planktonic foraminifera and calcareous nannoplankton updates the ages of the formations studied, proving younger than previously thought. The new definition of the Sub-Numidian stratigraphy enables a better correlation with equivalent successions widely outcropping along the Maghrebian, Betic, and southern Apennine Chains. The study proposes a new evolutionary tectonic/sedimentary model for this Tunisian sector of the Maghrebian Chain during the Paleogene after the Triassic–Cretaceous extensional regime. This paleogeographic reorganization is considered a consequence of the beginning of the tectonic inversion (from extensional to compressional), leading to the end of the preorogenic sedimentation. Our results suggest a non-tabular stratigraphy (marked by lateral changes of lithofacies, variable thicknesses, and the presence of diachronous boundaries) providing significant elements for a re-evaluation of active petroleum systems on the quality, volume, distribution, timing of oil generation, and on the migration and accumulation of the oil.

Updating the marine biostratigraphy of the Granada Basin (central Betic Cordillera). Insight for the Late Miocene palaeogeographic evolution of the Atlantic – Mediterranean seaway

The marine stratigraphic record of the Granada Basin (central Betic Cordillera, Spain) is composed of three Late Miocene genetic units deposited in different sea-level contexts (from base to top): Unit I (sea-level rise), Unit II (high sea-level), and Unit III (low sea-level). The latter mainly consists of evaporites precipitated in a shallow-basin setting. Biostratigraphic analyses based on planktonic foraminifera and calcareous nannoplankton indicate four late Tortonian bioevents (PF1-CN1, PF2, PF3, and PF4), which can be correlated with astronomically-dated events in other sections of the Mediterranean. PF1-CN1 (7.89 Ma) is characterized by the influx of the Globorotalia conomiozea group (including typical forms of Globorotalia mediterranea) and by the first common occurrence of Discoaster surculus; PF2 (7.84 Ma) is marked by the first common occurrence of Globorotalia suterae; PF3 (7.69 Ma) is typified by the influx of dextral Neogloboquadrina acostaensis; and PF4 (7.37 Ma) is defined by the influx of the Globorotalia menardii group II (dextral forms). The PF1 event occurred in the upper part of Unit I, whereas PF2 to PF4 events occurred successively within Unit II. The age of Unit III (evaporites) can only be estimated in its lower part based on the presence of dextral Globorotalia scitula, which, together with the absence of the first common occurrence of the G. conomiozea group (7.24 Ma), points to the latest Tortonian. Comparisons with data from the other Betic basins indicate that the evaporitic phase of the Granada Basin (7.37–7.24 Ma) is not synchronous with those from the Lorca Basin (7.80 Ma) and the Fortuna Basin (7.6 Ma). In the Bajo Segura Basin (easternmost Betic Cordillera), no evaporite deposition occurred during the late Tortonian. The evaporitic unit of the Granada Basin (central Betics) records the late Tortonian restriction of the Betic seaway (the marine connection between the Atlantic and Mediterranean). The diachrony in the restriction of the Betic seaway is related to differing tectonic movements in the central and eastern sectors of the Betic Cordillera.

Tectonic control on the sedimentary record of the central Moldavidian Basin (Eastern Carpathians, Romania)

The sedimentary record of the Tarcău and Vrancea Nappes, belonging to the flysch accretionary zone of the Eastern Carpathians (Eastern Carpathian Outer Flysch), registered Cretaceous-Miocene events during the evolution of the Moldavidian Basin. Our biostratigraphic data indicate that the deposits studied are younger than previously reported. The comparison of sedimentary record studied with the Late Cretaceous-Early Miocene global eustatic curve indicates that eustatic factor played a secondary role, after the tectonic one. Four main stages of different processes influenced by tectonics are recognized in the sedimentary record: (1) Campanian-Maastrichtian-earliest Paleocene; (2) latest Ypresian-Lutetian; (3) late Chattian-earliest Aquitanian, and (4) late Aquitanian-early Burdigalian. The late Chattian- earliest Aquitanian and late Aquitanian-early Burdigalian records indicate a high tectonic influence. The first event was related to the foredeep stage of the sedimentary domain studied, and the second one to the deformation stage of the same domain. The sedimentary records of tectonic influence recognized during these stages are useful tools for geodynamic reconstructions. The stratigraphic correlation of Tarcău and Vrancea sedimentary records are used

Stable oxygen and carbon isotope of foraminifera from DSDP Leg 90 sites

High-resolution oxygen and carbon isotope stratigraphy is presented for Miocene to early Pliocene sequences at three DSDP sites from the Lord Howe Rise, southwest Pacific, at water depths ranging from 1,300 to 2,000 m. Site 588 is located in the warm subtropics (~26°S), whereas Sites 590 and 591 are positioned in transitional (northern temperate) water masses (~31°S). Benthic foraminiferal oxygen and carbon isotope analyses were conducted on all sites; planktonic foraminiferal isotope data were generated for Site 590 only. Sample resolution in these sequences is on the order of 50,000 yr. or better. The chronological framework employed in this study is based largely upon ages assigned to Neogene calcareous nannoplankton boundaries. The benthic oxygen isotope record exhibits several major features during the Neogene. During most of the early Miocene, delta18O values were relatively low, reaching minimum values in the late early Miocene (19.5 to 16.5 Ma), and recording the climax of Neogene warmth. This was followed by a major increase in benthic delta18O values between ~16.5 and 13.5 Ma, which is interpreted as representing major, permanent accumulation of the East Antarctic ice sheet and cooling of bottom waters. During the 3 m.y. 18O enrichment, surface waters at these middle latitudes warmed between 16 and 14.5 Ma. During the remainder of the middle and late Miocene, benthic delta18O values exhibit distinct fluctuations, but the average value remained unchanged. The isotopic data show two distinct episodes of climatic cooling close to the middle/late Miocene boundary. The earliest of these events occurred between 12.5 and 11.5 Ma in the latest middle Miocene. The second cooling event occurred from 11 to 9 Ma, and is marked by some of the highest delta18O values of the entire Miocene. This was followed by relative warmth during the middle part of the late Miocene. The latest Miocene and earliest Pliocene (6.2 to 4.5 Ma) were marked by relatively high delta18O values, indicating increased cooling and glaciation. During the middle Pliocene, at about 3.4 Ma, a 0.4 per mil increase in benthic delta18O documents a net increase in average global ice volume and cooling of bottom waters. During this interval of increased glaciation, surface waters warmed by 2-3°C in southern middle-latitude regions. During the late Pliocene, between 2.6 and 2.4 Ma, a further increase in delta18O occurred; this has been interpreted by previous workers as heralding the onset of Northern Hemisphere glaciation. Surface-water warming in the middle latitudes occurred in association with major high-latitude glacial increases in the early middle Miocene (16-14 Ma), middle Pliocene (-3.5 Ma), and late Pliocene (~2.4 Ma). These intervals were also marked by increases in the vertical temperature gradient in the open ocean. Intersite correlation is enhanced by using carbon isotope stratigraphy. The great similarity of the delta13C time-series records within and between ocean basins and with water depth clearly indicates that changes in oceanwide average delta13C of [HCO3]- in seawater dominated the records, rather than local effects. Broad changes in the Neogene delta13C record were caused largely by transfer of organic carbon between continental and oceanic reservoirs. These transfers were caused by marine transgressions and regressions on the continental margins. The dominant feature of Neogene delta13C stratigraphy is a broad late early to early middle Miocene increase of about lâ between ~19 and 14.5 Ma. This trend occurred contemporaneously with a period of maximum coastal onlap (transgression) and maximum Neogene climatic warmth. The delta13C trend terminated during the expansion of the Antarctic ice sheet and associated marine regression. The latest Miocene carbon isotope shift (of up to - 0.75 per mil) at 6.2 Ma is clearly recorded in all sites examined and was followed by relatively low values during the remainder of the Neogene. This shift was caused by a glacioeustatic sealevel lowering that exposed continental margins via regression and ultimately increased the flux of organic carbon to the deep sea. An increase in delta13C values during the early Pliocene (~5 to 4 Ma) resulted from marine transgression during a time of global warmth.