The Melilla carbonate complex (NE Morocco) is the only area of the Paleo-Mediterranean Sea where volcanic activity was present throughout most of the Messinian. 40Ar/39Ar dating of volcanic tuffs interbedded within the upper Messinian sedimentary deposits, known as the Terminal Carbonate Complex (TCC), yields accurate ages of paleoenvironmental and sea-level changes related to the Messinian Salinity Crisis. The new chronologic data (1) provide an average of 5.95–5.99 Ma for the base of the TCC, thus being synchronous with the onset of the Messinian Salinity Crisis, (2) demonstrate for the first time that the basal unconformity of the TCC does not represent a hiatus of long duration, (3) define a precise time line at 5.87±0.02 Ma (2σ) corresponding to sedimentary rocks exhibiting a lateral transition between continental and marine deposits typical of the TCC and (4) yield evidence that emersion of the Melilla platform during deposition of the TCC is partly related to tectono-magmatic activity. An erosional surface, capping the TCC deposits in the Melilla basin, is related to the major Messinian Mediterranean drawdown. The duration of the hiatus, associated with this surface, is estimated to be at most 450 kyr, but is probably shorter.

Four holes were drilled at two sites in the western North Atlantic during Deep Sea Drilling Project Leg 76. Thick Pliocene-Quaternary sediments were continuously cored in Holes 533 and 533A, located on the Blake Outer Ridge. A detailed biostratigraphic study of the upper Neogene and Quaternary strata has been made using distribution of planktonic foraminifers. Precision of the biostratigraphic analysis enabled us to trace fluctuations of the sedimentation rate closely. Very high mid-Pliocene input strongly contrasts with the extreme condensation that was noted to have occurred during the latest Pliocene. Quantitative micropaleontology methods have been applied to selected planktonic species or groups of foraminifers, enabling us to discern clearly the oceanic response to large-scale climatic changes, such as the mid-Pliocene glacial event and the Quaternary cycles. In contrast, the small-scale climatic events appeared to be obscured by minor sedimentary disturbances, which could be related to bottom contour-following currents.

New field investigations in the Cape des Trois Fourches peninsula (northern Morocco) allow us to bring new insights on the late Messinian erosional surface and the overlying marine deposits. Our results show that the late Messinian erosional surface, characterized by an erosional plateau, is interrupted by an up to 70 m deep paleovalley, thought to result from a landslide. The minimum relative sea-level drop is 70 m, probably much more with regard to the indication that a large-scale landsliding has occurred. The post-erosional deposits (Cycle 3) comprise one major depositional sequence composed of two high-order sedimentary subcycles. Deposits of the first subcycle 3A filled in the erosional basin and the paleovalleys; deposits of the second subcycle 3B overflowed the paleovalleys and the erosional plateau. We found evidence of the transgressive systems tract of the deposits corresponding to the post-Messinian crisis reflooding, for which a latest Messinian onset can neither be proved nor entirely ruled out because the rare biostratigraphic data are not sufficiently conclusive. The uppermost part of the reflooding deposits (subcycle 3A) is shown to be definitely Pliocene in age based on the occurrence of Globorotalia puncticulata and the composition of the assemblage of pectinids.

The opening of the Equatorial Atlantic Gateway (EAG) during the Cretaceous was accompanied by the disruption of the sedimentary basins that had developed on the conjugate margins of Africa and South America. Drilling along the Côte d'Ivoire–Ghana Transform Margin (ODP Leg 159) provided a transect across the northern rim of this gateway. The interplay of tectonic and oceanic processes along the gateway created a complex continental margin that evolved in three stages interrupted by dramatic changes in sedimentary facies, waterdepths, and subsidence rates. The earliest stage records the formation of small basins with restricted connection to the world ocean and rapid infill with siliciclastic deposits in an Early Cretaceous intracratonic rift or wrench tectonic setting. This stage ended with an uplift event and the formation of a regional unconformity. During the late Albian to middle Coniacian, the oceanward side of the margin subsided below the calcite compensation depth (CCD) and a deepwater connection between Central and South Atlantic became established. Deepening of the basement ridge and its landward slope, in contrast, were delayed and detrital limestones intercalated with carbonaceous shales accumulated at shelf to slope depths. During the ensuing, latest Cretaceous to present stage, passive margin subsidence led to continuous deepening of the basement ridge and on its landward slope. Condensation and gradually decreasing organic contents point to an intensified exposure to deepwater circulation. The replacement of the zonal circulation system through the Mesozoic Tethys and Central Atlantic with a modern, oxidizing meridional circulation system through the EAG appears to be intimately related to the changing depositional conditions over large parts of the Cretaceous Atlantic.

During Ocean Drilling Program Leg 171B, an Aptian to Turonian sedimentary succession yielding exceptionally well-preserved planktonic foraminiferal faunas was recovered at Sites 1049, 1050, and 1052. Most of the standard Tethyan planktonic foraminiferal zones have been recognized within the mid-Cretaceous section, with the exception of two Albian zones not reached by any of the drilled holes. In addition, some emphasis is brought here on the current problems concerning the definition of the Aptian/Albian and Albian/Cenomanian boundaries.

The diversity record of abyssal agglutinated foraminifera reveals specific intervals during the past 150 million years when the diversity of species and ecological partitioning was high, interspersed by periods of lower diversity. We distinguish herein three faunas recovered from abyssal red claystones that represent periods of widespread oligotrophic conditions with low rates of sea-floor organic carbon flux. These are termed: the Tithonian to Barremian "Argo Fauna" the Turonian-Maastrichtian ''Krashenninikov fauna'', and the Eocene to early Oligocene "Iberia-Celebes Fauna". A fourth fauna (the mid-Cretaceous "Hatteras Fauna" and the "Biofacies B Faunas") is observed during intervals characterised by eutrophic conditions that result in high organic flux and poorly oxygenated conditions at the sea floor.The taxonomic composition, diversity, and microhabitat preferences of agglutinated foraminiferal faunas in Cretaceous to Cainozoic deep sea sediments are related to a combination of environmental factors, including depth nf thp calcite compensation depth, ventilation of the bottom waters, and the amount of sea floor organic flux. These environmental conditions have changed in different ocean basins at different times and consequently the paleobiogeographical patterns of "Deep water agglutinated foraminifera" (DWAF) reflect general circulation patterns and resulting trophic conditions.We believe that the ecological structuring of agglutinated foraminifera within habitats may have been one of the most important driving forces in the evolution of this group. We conclude that the diversification of distinctive abyssal assemblages at specific times in ocean history depends upon the establishment of oligotrophic conditions in the deep sea following perturbations to the trophic structure caused by periods of increased organic carbon flux. Our comparison of Cretaceous to Recent DWAF reveals that evolutionary changes mainly tool; place among forms adapted to the oligotrophic end of the trophic resource continuum (i.e. passive deposit feeders, suspension feeders and some infaunal forms), whereas stasis prevailed among species adapted to eutrophic conditions (active epifaunal and shallow infaunal deposit feeders such as ammodiscids). Although the Neogene record of DWAF faunas is very poor, we observe that the modem sub-CCD fauna of the oligotrophic abyssal plains had its origins in the abyssal faunas of the Cretaceous and Paleogene.

Upper Cretaceous agglutinated foraminifer assemblages from Hole 959D of Ocean Drilling Program (ODP) Leg 159, Côte d'Ivoire-Ghana Transform Margin, reflect the subsidence history and paleoceanography of the widening equatorial Atlantic gateway.Five benthic foraminifer assemblage types are recognized: (1) Santonian and the lowermost Campanian assemblages (Cores 159-959D-65R and 64R) are characterized by the occurrence of bathyal calcareous benthic foraminifers with an increasing proportion of agglutinated foraminifers.The disappearance of calcareous foraminifers and assemblages exclusively composed of organically cemented agglutinated forms in Section 159-959D-65R-3 reflects the subsidence of the seafloor below the calcite compensation depth (CCD); (2) lower Campanian "biofacies B" assemblages (Cores 159-959D-63R through 61R) are exclusively composed of low-diversity agglutinated foraminifers, accompanied by abundant and occasionally well-preserved radiolarian assemblages; (3) middle Campanian to upper Maastrichtian deposits (Cores 159-959D-59R through 49R) contain an exclusively agglutinated Rzehakina epigona biofacies, which is well-known from middle to deep bathyal sites along the North Atlantic margins; (4) a change in agglutinated foraminifer assemblage composition toward morphologies commonly observed in present infaunal habitats and the common occurrence of the presumably infaunal genus Spiroplectammina are observed in Core 159-959D-48R.This change in agglutinated foraminifer assemblages corresponds to the Tethyan early Paleocene "Spiroplectammina event;" (5) a diversified Paleocene "Lizard Springs type" assemblage is characterized by several diverse Rzehakina, Saccamina, and Haplophragmoides species.Assemblages from Cores 159-959D-48R through 44R display high species diversity and reflect the deepest (lower bathyal to upper abyssal) paleobathymetry.Ranges of agglutinated foraminifer marker species and occurrences of paleoceanographic events within this biostratigraphic framework are almost identical to those observed in the North Atlantic, in the Western Tethys, and along the conjugate Brazilian margin.These observations lead us to confirm that a deep-water circulation system common to the North and South Atlantic has been active at least since the Santonian.

Cretaceous sediments from Ocean Drilling Program Leg 159 on the Cote d’Ivoire-Ghana Marginal Ridge (CIGMR), eastern equatorial Atlantic, are characterized by distinct stratigraphic changes in sedimentary facies associated with changes in the composition of the clayey and organic fractions, as well as of the calcareous nannofossil, radiolarian, foraminiferal, and palynomorph assemblages. In the absence of reliable magnetostratigraphic information, an integrated biostratigraphy provides the only means used to calibrate the geologic history of the Leg 159 area. The existence of marine depositional environments as early as the late Aptian to early Albian close to the Leg 159 drill sites puts constraints on the timing of the opening of the equatorial Atlantic gateway. Marine sedimentation on the ridge suggests that the West African and South American cratons were largely detached at this segment of the margin by the middle to late Albian. During the Cenomanian to Coniacian the ridge appears to have remained in an elevated position with concurrent low deposition or condensation (Site 959), high carbonate debris accumulation (Site 960), and even erosion (Site 962). Total organic Carbon measurements and microfaunal data lead us to suggest that, following the early opening of the seaway during the Albian, circulation remained restricted in the fragmented sub-basins of the CIGMR. It probably was not until the Santonian that a deep-water connection and circulation system became established between the Central and the South Atlantic. The sedimentary and faunal record at Site 959 show that a rapid subsidence occurred during the Santonian, with sub-calcite compensation depth conditions maintained until and beyond the Cretaceous/Tertiary boundary.

Lower Cretaceous benthic foraminiferal assemblages from basal sedimentary sequences of Holes 959D, 962B, and 962D provide time constraints for the onset of marine sedimentation on the Côte d'Ivoire-Ghana Transform Margin and show that marine conditions were already established by late Aptian-early Albian near Hole 959D and by mid to late Albian near Hole 962D.The foraminiferal data suggest that older Aptian-Albian marine sequences were subsequently reworked into upper Albian-lowermost Cenomanian sediments within tectonically active sub-basins.Marked fluctuations in test size, abundance, and diversity reflect a pulsed sedimentation pattern with an overall high accumulation rate.Three main cycles of deposition are detected from overall changes in preservation, abundance and diversity, which are possibly related to major shifts in sediment provenance and/or supply.The composition of the benthic foraminiferal assemblages at Holes 959D and 962D indicates an outer shelf to upper bathyal setting and reflects a combination of Tethyan, South Atlantic, and local endemic faunal influences, pointing to restricted connections with the open ocean and Tethys during the late Albian and early Cenomanian.There is no evidence for bottom-water anoxia or severe dysoxia during the deposition of Cores 159-962D-16R through 37R.The high dissolution of planktonic tests and absence or scarcity of benthic foraminifers in the upper part of the sequence (Sections 159-962D-7R-1 through 13R-1 and 159-962B-8H-5 through 9H-6) indicate some later deterioration in bottom-water oxygenation.

A high resolution carbonate carbon-isotope stratigraphy is established on bulk carbonates from the type locality of the Lower Aptian (= Bedoulian). This exceptionally expanded series permitted us to recognize two marked positive delta(13)C excursions. Correlation with the biostratigraphic data shows that the fi rst excursion commences im mediately after the Barremian-Aptian boundary and reaches maximum values within the Early Bedoulian. A second, more significant, positive shift begins in the middle part of the Late Bedoulian and reaches its maximum near the end of the Late Bedoulian. Already known from other pelagic Tethyan sites and even from the Pacific Ocean, this Upper Bedoulian excursion is regarded as global. The lower shift seems to be only recorded in sections with high carbonate accumulation rates such as La Bedoule and may fall into a strongly condensed interval or hiatus within the previously studied sections. ((C) Academie des sciences / Elsevier, Paris.).

During the Equanaute survey (June 1992), fourteen submersible dives were performed between 4950 and 2250 m water depths across the southern slope of the Cote d'Ivoire-Ghana Marginal Ridge (CIGMR), in the eastern Equatorial Atlantic. The CIGMR, a high-standing topographic marginal ridge along the Cote d'Ivoire-Ghana transform margin, is believed to result from a complex structural evolution due to the specific wrench-related rifting between Western Equatorial Africa and Northeastern Brazil, in Early Cretaceous times. In this paper we report and discuss geological observations made during dives, and sample analyses to resolve the lithology, paleoenvironmental conditions, age and origin of the CIGMR. The data help in better characterizing the different sedimentary and tectonic regimes which successively prevailed during the CIGMR formation and assessing the thermal regime operative during the fabrication and subsequent evolution of the margin. The thick sedimentary pile exposed along the southern CIGMR slope is made up of a repetitive elastic sequence indicative of a deltaic-to-prodeltaic environment. This sedimentary pile, of Early Cretaceous age, has recorded different stages of the transform margin structural evolution.(1) Syn-to post-lithification deformations first record extensional deformations related to the rifting of the adjacent northern divergent; margin segment (the Deep Ivorian Basin).(2) Wrench tectonics has, at a later stage, produced intense fracturing and participated in local folding; chiefly detected upslope. The integrated studies of geological samples and insitu observations obtained during the Equanaute survey support models. for transform margin evolution proposed mainly from geophysicaI data. (C) Elsevier, Paris.

Marry limestones from La Bedoule (Bouches-du-Rhone, SE France), historical type-locality of the lower Aptian, contain in their lowermost part a rich ammonite fauna belonging to the heteromorphic genus Pseudocrioceras. Up to the present this level, corresponding to the Pseudocrioceras coquandi Zone of Busnardo (1984), was considered by ammonitologists as early Aptian. However, a detailed study of newly collected faunas from both this level and immediately under-and overlying beds leads us to reconsider the age assignment of this interval. Our results show that the Pseudocrioceras are first accompanied, in the upper part of the Martelites sarnsini Zone, by a heteroceratid fauna showing a Barremian signature, and then coexist briefly with the first Deshayesitidae of the Aptian Deshayesites tuarkyricus Zone. Therefore, our proposal is to place the Barremian/Aptian boundary in the historical type-locality at the FAD (First Appearance Datum) of Deshayesites, being better defined and having a wider geographic extension in the Mesogean realm.

The Galicia Bank (Spain) exposes on its western slope a low-angle lithospheric syn-rift shear zone (a detachment fault) putting the upper continental basement of the margin (upper plate) into contact with serpentinized peridotite and gabbro (lower plate). The shear zone includes, from top to bottom: a) a cataclastic breccia, mixing angular and heterometric pieces from both the upper and lower plates; b) mylonites and ultramylonites, resulting from ductile to cataclastic deformation of gabbros and peridotites of the lower plate. A thin layer of post-rift basalt covers the cataclased peridotite on the oceanic side of the ocean-continent transition.

Different domains of the 285 rDNA of two planktonic foraminiferal species from the Mediterranean Sea have been amplified by PCR (Polymerase Chain Reaction) and sequenced. Comparison of the obtained sequences suggests that these unicellular organisms emerge early, close to an Amoeban group, in the eukaryotic phylogenetic tree.

During the EQUAMARGE II cruise (1988) along the Guinean continental margin (central Equatorial Atlantic) a 2.17 m long core has been sampled at 840 m water depth on the top of one of the volcanic seamounts cropping out in this area. Planktonic foraminiferal assemblages observed within the 2.13 m unconsolidated sediments indicate an age of 0.20 to 0.15 Ma, corresponding to the transition from interglacial to glacial events. Depth of deposition of the calcareous sand ranges between 150-200 m and progressively decreased during the glacial stage onset. Detailed sedimentological and micropaleontological studies, carried out on the 4 cm thick indurated core cap, indicate a deposition depth of 50-100 m, or even less. Taking into account the Pleistocene sea level fluctuations, these data suggest a rapid subsidence of the magmatic seamount since the upper most Pleistocene.

During the Equamarge II cruise (1988), several coring attempts made along the slope edge of the southern Guinean Plateau led to the recovery of middle Cretaceous sediments in two cores. One contained a carbonate block, dated as middle Albian (H. rischi Zone); the micropaleontological and sedimentological data suggest an open marine environment and paleodepths of approximately 150–200 m. Another core included a dark shale level corresponding to the global anoxic event “CTBE” (Cenomanian/Turonian Boundary Event, W. archaeocretacea Zone). As shown by seismic reflection profiles, these mid-Cretaceous beds lie very close to a major unconformity, which distinctly divides the sedimentary cover into two units (the lower one folded and faulted, the upper one undisturbed). Geodynamic and paleoenvironmental implications of these new data better constrain models of evolution for this crucial area of the Atlantic realm. The compressive and extensional events which affected the Equatorial Atlantic during the progressive separation of Africa from South America are thus more accurately dated. These results also strengthen the hypothesis of an open seaway between the Central and South proto-Atlantic as early as the middle Albian.

The biostratigraphic correlation scheme of Upper Cretaceous multicoloured claystones in the Polish Romanian. External Carpathians using agglutinated deep-water foraminifers can be extended to onshore localities in the Gibraltar Arch area (Morocco, Spain) and DSDP/ODP sites in the North Atlantic. In all studied areas, taxonomic turnovers in deep-water agglutinated foraminifers are observed at the Cenomanian-Turonian boundary and in the early/middle Campanian. Additionally, a remarkable decrease in abundance and diversity of benthic agglutinated foraminifers is observed at the same levels in continuous sections of North Atlantic DSDP sites. These datum levels correspond to inter-regional and time-constant palaeoceanographic events, and may facilitate the direct correlation of the biozonation of agglutinated foraminifers to the standard geomagnetic polarity time scale.

A reexamination of the agglutinated benthic foraminiferal microfaunas found in the Upper Cretaceous red and brown clays of DSDP Hole 603B and ODP Holes 604A and 641A allows us to refine the initial shipboard biostratigraphic interpretation and to propose a fourfold zonation that can be used with some precautions in the oceanic realm. By means of various calibrations, an attempt is also made to integrate this zonation in a worldwide chronostratigraphic framework. The resulting chronologic control permits us to discern large differences in the rhythm of red clay deposition on either side of the North Atlantic Ocean. -Authors