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International audience; The French Massif Central represents one of the rare occurrences in Europe where lower Pleistocene fossil deposits are associated to a substantial volcanic activity. Thanks to the abundance of volcanic zircons in the differentiated products of the Monts-Dore/Gu´ery stratovolcano, we were able for the first time to use U/Pb geochronology on zircon to precisely date lower Pleistocene fossil deposits. Zircon, a weathering-proof heavy mineral, was dispersed over the landscape through Plinian eruptions, and quickly reworked in fossil-bearing sedimentary deposits. Five Villafranchian fossil sites in the Upper Allier River valley (French Massif Central) have been precisely dated: Chilhac (MNQ17b, 2.285 ± 0.046 Ma), Mont Coupet (2.274 ± 0.032 Ma), Sen`eze (reference locality for MNQ18, 2.100 ± 0.029 Ma, confirming the previously determined 2.18–2.10 Ma 40Ar/39Ar ages), Blassac-La Girondie (MNQ19, 1.946 ± 0.029 Ma), and Vazeilles (1.843 ± 0.028 Ma). These new chronological data constrain the duration of the MNQ18 in central France to about 200 ka. The confirmation of an old age for the Blassac-La Girondie deposit indicates that the MNQ19 biozone started significantly earlier thanpreviously thought.

The aim of this thesis focus on the restitution of the hydrology of intermediate and deep water masses during the last 24 ka in the Mediterranean Sea in the Siculo-Tunisian Strait.We firstly generated high-resolution biochronological records extending from the last glacial period. These records are based on oxygen isotopic analyses, micropaleontology (planktonic foraminifera) and surface water temperature (SST) carried out along 4 deep-sea sediment cores collected in the Siculo-Tunisian Strait, in the Tyrrhenian Sea, in the Ionian Sea and in the Levantine basin respectively. The quantitative distribution of planktonic foraminifers allowed to identify seven biozones based on the appearance and / or disappearance of the main taxa or their peaks of abundance. The abundance records show that the major changes in the planktonic foraminifera assemblages are similar in the central and western basins. Indeed, 4 bioevents have been recognized and can be used as reference markers to establish or improve the chronology of marine sediment cores from the Mediterranean basin.Successively, we have reconstructed changes in the ventilation rate of the intermediate and deep water masses since the last glacial period by measuring the 14C age difference between monospecific species of benthic and planktonic foraminifera (BP) recovered from deep seas cores bathed by intermediate and deep water masses (KET80-37 and REC13-53). The results show that the deposition of the last Sapropel S1 does not require a period of preconditioning, often evoked by climate models to explain the time lag between the beginning of the increase in the Nile river flow and the start of the establishment of S1., Les objectifs de cette thèse se focalisent sur la restitution de l’hydrologie des masses d’eaux intermédiaires et profondes au cours des derniers 24 ka en mer Méditerranée dans le détroit Siculo-Tunisien.Nous avons généré, dans un premier temps, des enregistrements biochronologiques à haute résolution s’étendant depuis la dernière période glaciaire. Ces enregistrements sont basés sur des analyses isotopiques de l’oxygène, micropaléontologiques (foraminifères planctoniques) et de température des eaux de surface (SST) effectuée le long de 4 carottes de sédiments mains profonds prélevées dans le détroit Siculo-Tunisien, en mer Tyrrhénienne, en mer Ionienne et dans le bassin Levantin respectivement. Les modèles de distribution quantitatifs des foraminifères planctoniques ont permis d’identifier sept biozones en se basant sur l’apparition et/ou la disparition des principaux taxons ou de leurs pics d’abondance. Les enregistrements d’abondance montrent que les changements majeurs dans les assemblages de foraminifères planctoniques présentent sont similaires principalement dans les bassins central et occidental. En effet, 4 bioévènements ont été reconnus et peuvent être utilisé comme marqueurs de référence pour établir ou améliorer la chronologie des carottes de sédiments marines du bassin méditerranéen.Dans un deuxième temps, et dans le cadre de la restitution des éventuelles variations du temps de ventilation des masses d’eaux plus profondes depuis la dernière période glaciaire, nos résultats basés sur les mesures de la différence d’âge 14C entre des espèces monospécifiques de foraminifères benthiques et planctoniques (B-P) prélevées dans des carottes marines baignées par des masses d’eaux intermédiaires et profondes (KET80-37 et REC13-53), respectivement démontrent que le dépôt du dernier sapropel S1 ne nécessite pas une phase de préconditionnement, longtemps évoquée par les modèles climatiques pour expliquer le décalage entre le début de l’augmentation du débit du Nil et l’amorce de la mise en place de S1.

We generated high-resolution biochronological records in the Mediterranean Sea covering the period extending to the Late-glacial. The present study is based on micropaleontological, sea-surface temperature (SST) and oxygen isotopic analyses performed along three well-dated deep-sea cores: REC1353, KET80–19 and MD84–641 recovered in the Siculo-Tunisian Strait, Tyrrhenian Sea and Levantine Basin, respectively. The quantitative distributional patterns of planktic foraminifera permitted to identify seven biozones based on the apparition and/or disappearance of the main specific taxa or by their noticeable abundance peaks. Abundance records display that major changes in planktic foraminiferal assemblages have a similar pattern mainly in central and western basins. In particular, four recognized bio-events can be used to establish or to improve the chronology of Mediterranean deep-sea cores. The comparison of the SST estimates and foraminiferal records with those of NGRIP ice-core shows a similarity between the Greenland climate and the Mediterranean hydrology. This indicates that the main climate changes recorded in the North Atlantic are globally in phase with those observed in the Mediterranean region.

International audience; The biostratigraphic distribution of orbitolinids for the Barremian of SE France proposed hereafter is calibrated on the ammonite biozonation. This work is based on the study of eleven sections with orbitolinids associated to macrofossils (ammonites and/or echinids) significant in terms of biostratigraphy or overlain with levels bearing the above macrofossils.

The Cenomanian—Turonian boundary is marked by worldwide paleoenvironmental and paleoceanographical changes that are associated with a perturbation of the global carbon cycle and black shale deposition, called the Oceanic Anoxic Event 2 (OAE2). The objective of this study is to precisely characterize the nature of the organic matter, its variability, paleoenvironmental significance and the preservation conditions of two areas located along the northwest African Shelf where large-scale organic carbon burial contributed significantly to the global carbon burial associated with OAE2. With these premises, an organic petrographic and geochemical approach to the Cenomanian—Turonian record of the Moroccan Atlantic coast allowed the definition of the variability of the organic facies and the paleoenvironmental characterization of the upper Cenomanian—lower Turonian sediments of the Agadir section (Agadir Basin) and of the lower Turonian record of the Amma Fatma section (Tarfaya Basin). At Agadir, the marine microplankton dominated assemblages, with variable degree of amorphization, allowed the characterization of a transgressive-regressive cycle during the upper Cenomanian followed, during the lower Turonian, by a drowning event with establishment of a deep platform environment (under reducing conditions, increase in EFU, EFV, EFMo). The base of the succession (base of W. archaeocretacea biozone) and the top of the upper Cenomanian are characterized by two sea-level lowstands, and a high energy oxic environment, that culminate in emersion surfaces (high EFMn and low organic matter preservation). The organic facies in the lower Turonian of Amma Fatma is largely dominated by bacterial material (probably derived from sulfur bacteria), indicating an outer shelf setting, with some degree of restriction, under euxinic conditions (high EFMo) and high primary productivity (high EFCu, EFNi, EFZn). Differences in terms of the redox conditions between the two basins during the lower Turonian were determined, with anoxia prevailing at Agadir, while euxinic conditions are established at Tarfaya. These are explained by different oceanic circulation patterns, with the mixing of Tethyan waters at Agadir. High primary productivity is recorded at both locations, possibly promoted by the occurrence of upwelling currents. This study further corroborates a delay in the anoxia in Agadir, that during the isotopic excursion of OAE2 only reaches slight dysoxia (upper Cenomanian), and the maintenance of reducing conditions in Tarfaya post-OAE2.

The acritarch genus Orthosphaeridium Eisenack 1968 is one of the most frequently recorded acritarch taxa in the Ordovician. The taxonomy of this easily recognizable genus is revised herein based on a detailed literature review and on new investigations of palynological material from northeastern Iran and South China. The review confirms that Baltisphaera Burmann 1970 is a junior synonym of Orthosphaeridium of which the diagnosis is here emended. Over 20 species have been described in the literature, but many of them are apparently synonyms. The review indicates that the following four species can be easily differentiated: Orthosphaeridium bispinosum Turner 1984, Orthosphaeridium ternatum (Burmann 1970) Eisenack et al. 1976, Orthosphaeridium rectangulare (Eisenack 1963) Eisenack 1968 (type species) and Orthosphaeridium octospinosum Eisenack 1968. The taxonomical ranks of Orthosphaeridium rectangulare var. quadricornis Burmann 1970 and Orthosphaeridium octospinosum var. insculptum Loeblich 1970 are changed from the species to the varietas level. The review indicates that Orthosphaeridium first appeared in South China in the Expansograptus hirundo graptolite Biozone, i.e. in the early Dapingian (stage slice Dp1 and time slice 3a of the Middle Ordovician) and that it reached a global distribution during the Middle and Late Ordovician. The genus disappeared at the end of the Ordovician and has never been recorded from the Silurian. The genus is thus a stratigraphical index fossil for the Middle and Late Ordovician. Orthosphaeridium has been recorded from the margins of all paleocontinents and paleoecologically seems to be an eurythermic taxon.

International audience; The stratigraphic distribution of larger benthic foraminifera and other microfossils, as analysed in thin-sections, has been investigated in three stratigraphic sections from the island of Mallorca (Son Maina, S’Heretat and Cuevas de Artà). These stratigraphic sections represent deposition in a Lower Jurassic shallow-water carbonate platform succession (Es Barraca Member, Soller Formation) of the Llevant Mountains. The microfossil assemblages contain abundant benthic foraminifera and calcareous algae, including the typical Liassic dasycladalean alga Palaeodasycladus mediterraneus (Pia) and the microproblematica Thaumatoporella parvovesiculifera (Raineri), which provide good age constraint of the succession. Three consecutive biozones have been recognized based on the stratigraphic distribution of foraminifera, including the evolutionary bioseries Mesoendothyra—Lituosepta—Orbitopsella spp., which are documented for the first time in the Balearic Basin: Biozone A (interval Zone) is characterized by the occurrence of small Siphovalvulina spp., Mesoendothyra sp. and rare Lituosepta ancestors. Biozone B (lineage Zone), whose lower boundary is defined by the first occurrence of Lituosepta recoarensis Cati and its top by the first appearance of Orbitopsella aff. primaeva (Henson). The uppermost part of biozone B shows an interval with transitional morphotypes between Lituosepta and Orbitopsella, indicating that the change between biozones B and C1 is gradual (B/C1 transition). This interval is characterized by the presence of very primitive forms of Orbitopsella. Finally, Biozone C1 (lineage Zone) is defined by the first occurrence of Orbitopsella aff. primaeva together with L. recoarensis. The upper boundary of the Biozone C1, which is defined by the first occurrence of O. praecursor s.l., is not recorded in the studied sections of the Es Barraca Member. This biostratigraphic zonation is consistent with a Sinemurian age for the Es Barraca Member with its top most likely not extending into the Pliensbachian. The proposed biostratigraphic scheme is comparable with those established for other western Tethyan margins such as the High Atlas of Morocco, the Southern Italian Alps or the Dinaric Alps of Slovenia and Croatia. The reconstruction of a depositional transect across the studied sections shows the progressive loss of the upper biozones towards the northeast, demonstrating the existence of significant hiatuses in some sections of the Llevant Mountains domain. These hiatuses point to an intra-lower Pliensbachian (Carixian) early stage of platform fragmentation, with areas affected by erosion or non-deposition, and areas with marine marly limestone sedimentation followed by deltaic siliciclastic progradation on the north-western part of Mallorca.

A new occurrence of the onychochilid mollusc Pelecyogyra is reported from the late Floian Landeyran Formation (Apatokephalus incisus Biozone) in the Montagne Noire, southern France, where it is associated with the two tergomyans Carcassonnella courtessolei and Thoralispira laevis, and a mollusc indet. With a low cap-shaped shell. The Montagne Noire specimens compare morphologically with Pelecyogyra fezouataensis from the late Tremadocian Fezouata Formation (Araneograptus murrayi Biozone) in Morocco and are tentatively referred to this species. Each occurrence of Pelecyogyra is from one or two localities only, but separated in time. They differ further in the deeper facies, association with Carcassonnella and Thoralispira, and non-gregarious occurrence in Montagne Noire compared to the shallower facies, lack of other molluscs and gregarious occurrence in the Fezouata Formation. In the Lower Ordovician, Pelecyogyra, Carcassonnella courtessolei, the rare C. vizcainoi and Thoralispira laevis are taxa that occur only in Montage Noire and the Anti-Atlas, while Lesueurilla prima also occurs in the Prague basin of the Czech Republic. Contrary to other faunal elements, like echinoderms and trilobites, these genera seem to have a wide environmental tolerance and are long ranging taxa. The main occurrence of the three key taxa Carcassonnella, Thoralispira and Lesueurilla in the Montagne Noire is in the lower part of the La Maurerie Formation (Taihungshania miqueli acme Zone), while the same taxa appear just slightly later in Morocco (?Cymatograptus protobalticus Biozone). Migration to the Anti-Atlas during the early Floian seems to have been possible during a period of general faunal exchange. Pelecyogyra may either have migrated from the Anti-Atlas to Montagne Noire during the same interval or possibly during the late Floian as indicated by shared faunal elements between these two regions at that time.

International audience; In part 1 of this work we discussed the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on prevailing practical methods for correlation in that J/K interval, traditional usage and the consensus over the best boundary markers that had developed in the last forty years. This consensus has developed further, based on the results of multidisciplinary studies on numerous sites over the last decade. Here in Part 2 we give an account of the application of those results by the Berriasian Working Group (ISCS), and present the stratigraphic evidence that justifies the selection of the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. We describe a 45 m-thick section in the Calcaires Blancs vocontiens – that part of the formation covering the calpio­nellid Chitinoidella, Remanei. Intermedia, Colomi, Alpina, Ferasini, Elliptica and Simplex biozones. The stratigraphic data collected here has been compiled as part of a wider comparative study of complementary Vocontian Basin sites (with localities at Charens, St Bertrand, Belvedere and Le Chouet). Evidence from Tré Maroua thus sits in this substantial regional biostratigraphic and magnetostratigraphic context. For the purposes of the GSSP definition, here we particularly concentrate on the unbroken sequence and biotic markers in the interval immediately below the boundary, the Colomi Subzone (covering circa 675,000 years), and immediately above, the Alpina Subzone (covering circa 725,000 years). Particularly significant fossil datums identified in the Tré Maroua profile are the primary basal Berriasian marker, the base of the Alpina Subzone (a widespread event marked by dominance of small Calpionella alpina, with rare Crassicollaria parvula and Tintinopsella carpathica): the base of the Berriasian Stage is placed at the base of bed 14, which coincides with the base of the Alpina Subzone. Secondary markers bracketing the base of the Calpionella Zone are the FOs of the calcareous nannofossil species Nannoconus wintereri, close below the boundary, and the FO of Nannoconus steinmannii minor, close above. The Tithonian/Berriasian boundary level occurs within M19n.2n, in common with many documented sites, and is just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We present data which is congruent with magnetostratigraphic and biostratigraphic data from other key localities in France and in wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theodosia…), and thus the characteristics and datums identified at Tré Maroua are key for correlation and, in general, they typify the J/K boundary interval in Tethys and connected seas.

An exceptional buildup of thin-shelled bivalves (3.5 m thick and more than 12 m long), apparently the largest in the literature, is reported from the External Subbetic (Betic Cordillera, southern Spain). Calcareous nannofossils indicate the NJT8 biozone (late Aalenian) below the buildup and the NJT9 biozone (early Bajocian) at the base of the buildup. The thin-shelled bivalves, commonly referred to as filaments, are Bositra-like forms, an opportunistic bivalve that flourished under stressed conditions. Geochemical proxies (carbon isotopes, P-org and Ba-bio, and Cr/Al, V/Al and Ni/Co ratios) indicate that the marine environment was subjected to changes in oxygenation and trophic conditions, which, under the optimum states, promoted extremely high rates of production of the thin-shelled bivalves. The large buildup accumulated on the sea-floor under favorable hydrodynamic conditions and local topography. The significance of these depositional characteristics in relation to the previous literature is discussed.

Estimating biodiversity and its variations through geologic time is a notoriously difficult task, due to several taphonomic and methodological effects that make the reconstructed signal potentially distinct from the unknown, original one. Through a simulation approach, we examine the effect of a major, surprisingly still understudied, source of potential disturbance: the effect of time discretization through biochronological construction, which generates spurious coexistences of taxa within discrete time intervals (i.e., biozones), and thus potentially makes continuous- and discrete-time biodiversity curves very different. Focusing on the taxonomic-richness dimension of biodiversity (including estimates of origination and extinction rates), our approach relies on generation of random continuous-time richness curves, which are then time-discretized to estimate the noise generated by this manipulation. A broad spectrum of data-set parameters (including average taxon longevity and biozone duration, total number of taxa, and simulated time interval) is evaluated through sensitivity analysis. We show that the deteriorating effect of time discretization on the richness signal depends highly on such parameters, most particularly on average biozone duration and taxonomic longevity because of their direct relationship with the number of false coexistences generated by time discretization. With several worst-case but realistic parameter combinations (e.g., when relatively short-lived taxa are analyzed in a long-ranging biozone framework), the original and time-discretized richness curves can ultimately show a very weak to zero correlation, making these two time series independent. Based on these simulation results, we propose a simple algorithm allowing the back-transformation of a discrete-time taxonomic-richness data set, as customarily constructed by paleontologists, into a continuous-time data set. We show that the reconstructed richness curve obtained this way fits the original signal much more closely, even when the parameter combination of the original data set is particularly adverse to an effective time-discretized reconstruction.

The Taidon and Fomin formations of the Kuznetsk Basin (SW Siberia, Russia) were sampled in three sections, Old Belovo quarry, Artyshta village and Starobachaty village. The carbonate beds revealed microfacies of bioclastic wackestone and packstone, deposited in the distal parts of inner ramps and the proximal parts of mid ramps. Relatively rare plurilocular foraminifers occur in bioclastic neomicrosparitized wackestone deposited in the shallower parts of the carbonate ramp. The other microfacies only contain the bilocular foraminifer genus Earlandia. The plurilocular foraminifers permit the dating of the lower part of the Taidon Formation and the distinction of a biozone characterized by Tuberendothyra, Pseudoplanoendothyra, and Granuliferella. This local biozone can be correlated with the MFZ4 reference-biozone established in Belgium, which is late Hastarian (i.e., latest early Tournaisian) in age. Conodonts of the upper Siphonodella crenulata Zone in the lower part of Taidon Formation are consistent with this late Hastarian age. The Fomin Formation cannot be directly dated by its foraminifers Earlandia. As it is overlain by previously dated lower Visean beds, the Fomin Formation corresponds to all or part of the entire Ivorian (i.e., late Tournaisian) and of the MFZ5 to MFZ8 biozones. The same uncertainty on the late Tournaisian age exists with the conodonts, which belong to the lower Siphonodella crenulata Zone and isosticha-upper crenulata/typicus/anchoralis-latus zones, respectively. As a taxonomical result, Septabrunsiinoidea n. superfam. is introduced, in order to explain some poorly known lineages of the Tournaisian. Palaeobiogeographically, SW Siberia is proposed as the radiation centre of the Septabrunsiinoidea during the Tournaisian, and especially during the Hastarian, and their migration centre toward three directions: North America, South China and western Tethyan areas.

International audience; This study characterizes the stratigraphical context as well as the palaeoenvironmental and sea-level trends during the Late Frasnian and Famennian in the Buschteich section (Thuringia, Germany). An integrated approach combines conodont biostratigraphy, chemostratigraphy based on carbon and oxygen isotopes , conodont biofacies analyses and investigations of the morphotypes of foraminifera that occur in the section was applied. Conodonts provided a fine-scale biostratigraphical framework. All the Famennian con-odont biozones were identified, with the exception of the three lowest. The Frasnian-Famennian transition was further identified by a positive carbon isotope excursion. This continuous Famennian record is developed in a condensed limestone succession. The reddish Griotte facies, typical of strata of this period, were not documented. Black shales were not developed except for an interval of dark colored mud rocks corresponding to the Hangenberg event at the top of the section. The carbonate succession of Buschteich was deposited in an outer ramp environment, pelagic organisms are the dominant fauna. This is corroborated by the overall dominance of the deep-water conodont genus Palmatolepis. Microfacies, conodont biofacies and foramini-fera indicated a deepening trend from the Lower crepida to the Lower rhomboidea Zone, followed by a shal-lowing trend from the Upper rhomboidea to the praesulcata Zone. This sequence overall matches the sea level reference curve for Euramerica. The timing of maximum water depth at Buschteich, as well as the general sea-level reference record, differs from the Col des Tribes (Montagne Noire, France). Differential uplift or overprinting of the long-term eustatic changes may be the cause of the discrepancy in the local sea-level records.

International audience; This contribution deals with the Middle to early Late Ordovician of the Armorican Massif (western France). Theaim is to reconstruct a multi-order eustatic curve from the stratigraphic record. The studied section (CrozonPeninsula area) shows sediments deposited in tidal to storm-dominated shelf environments. A sequence analysis(facies and stacking pattern analyses), combined with a gamma-ray record and a backstripping procedure, wascarried out. Chitinozoan assemblages provide the biostratigraphic framework including time calibration.The stratigraphic succession is dominated by the stacking of sequences representing different orders of sea-levelchange i.e. very high- (b400 kyr), high- (400 kyr) and low- (3rd order) frequencies. Atime-calibratedsea-levelhigh frequency curve, corrected for compaction, sediment load and tectonic subsidence, has been calculatedbased on a backstripping procedure. The smoothing of this curve permits identification of eleven thirdordersequenceswith seven episodes of significant (50 to 80m) and rapid (less than 100 kyr) sea-level falls duringthe Darriwilian and the Sandbian, and two major transgressive events located in the formosa and pissotensisbiozones of the Darriwilian. The reconstructed sea-level curve reveals thatmost of the third-order cycles comprisethree fourth-order cycles of assumed 400 kyr duration. This 1.2 myr duration of the Ordovician thirdordersequencessuggests that they may be related to long-period obliquity cycles, an orbital forcing characteristicof icehouse sequences in the late Cenozoic and the Quaternary. These results imply that themajor part of theMiddleand early Late Ordovician was characterized by icehouse conditions and third-orderglacio-eustatic cycles.A time calibration of the chitinozoan biozones was developed from the sequential analysis. It suggests that theearly Darriwilian biozones (from henryi to calix biozones) have short durations of several 10 to several 100 kyrwhereas the pissotensis Biozone has a temporal extent of several myr, extending into the early Sandbian.

The ages of critical periods in the geological record of the Earth have to be determined and attached uncertainties quantified as precisely and accurately as possible. This study tries to find an optimal strategy for sampling, for both biochronology and high-precision U–Pb analysis of zircon from ash beds, and for the selection and statistical treatment of geochronological data. This strategy is applied to the case of the Early–Middle Triassic boundary (EMTB) in the southern Nanpanjiang Basin in South China, aiming to obtain the most accurate age information for this boundary with an associated uncertainty. The EMTB has been located in a sedimentary section near Monggan, Guangxi, South China, which permitted tight correlation between conodont biozones, the carbon isotopic record, and high-precision zircon U–Pb data from volcanic ashes. Two residual maximal horizons were defined using characteristic associations of conodont species, accurately bracketing the EMTB. The lower and upper age limits of these horizons, as well as the first occurrence (FO) of the base Middle Triassic index fossil Chiosella timorensis , were numerically calibrated by high-precision chemical abrasion, isotope dilution, thermal ionization mass spectrometry (CA-ID-TIMS) U–Pb dates. Volcanic zircon in the analyzed ash beds reveals complex system behavior, in particular (i) unresolved lead loss after chemical abrasion, and (ii) pre-eruptive growth and/or recycling of zircon crystals, leading to excess scatter in 206 Pb/ 238 U dates and to violations of the stratigraphic sequence. A sufficiently high number of closely spaced ash samples (N) and of U–Pb analyses per sample (n) promotes recognition of such complications. Two different age models were constructed from weighted mean 206 Pb/ 238 U dates, comparing smoothing cubic spline and Bayesian interpolation approaches. The statistical treatment of the combined datasets allows quantification of the lower and upper limits and associated uncertainties of the two conodont biozones as well as of the FO of C. timorensis . The age for the EMTB is calculated from combined interpolated data at 247.05 ± 0.16 Ma. The age model derived from Bayesian interpolation is considered to be more adapted to the present case, where discontinuous changes in sedimentation rates are expected to be important. The smoothing spline represents a more parsimonious model, producing a simpler solution in terms of smoothness, but the model assumptions are too strong for many geological problems. The additional freedom in constructing the Bayesian interpolating curve presumably leads to more realistic, albeit larger confidence intervals.

International audience; Pelecyogyra fezouataensis nov. gen., nov. sp. is described from the Lower Ordovician (Tremadocian, A. murrayi Biozone) Fezouata Formation at Oued Beni Zoli (locality Z-F5), in the central Anti-Atlas, Morocco. This is the first Onychochilidae Koken in Koken and Perner, 1925 reported from the Ordovician of Morocco. Its stratigraphical position bridges the gap between the late Cambrian and Middle to Upper Ordovician records. This new taxon draws together large specimens, reaching 27 mm in the greatest diameter, with 3 rapidly expanding whorls. All specimens are invariably preserved as dorsoventrally compressed moulds although preservation suggests that the degree of compaction was not great and that the species was generally low spired. A characteristic axe-shaped apertural lip and an ornamentation consisting of fine and dense lirae serve to distinguish the new genus from other onychochilids. The species appears to have been gregarious. In some specimens, small scalloped injuries are preserved along the apertural margins but these are not considered to reflect failed predation. Up to now, twenty-two species and eight genera of Ordovician onychochilids have been documented, being distributed in eight different terranes. The composition of the Onychochilidae is briefly reviewed and updated from the literature, to include Helicotis? Koken in Koken and Perner, 1925, Hyperstrophema Horný, 1964, Invertospira Horný, 1964, Kobayashiella Endo, 1937, Laeogyra Perner, 1903, Matherella Walcott, 1912, Matherellina Kobayashi, 1937, Onychochilus Lindström, 1884, Pelecyogyra nov. gen., Pervertina Horný, 1964, Scaevogyra Whitfield, 1878, Sinistracirsa Cossmann, 1908, Versispira Perner, 1903, and Voskopiella Frýda, 1992. Onychochilidae and Clisospiridae are placed in Mimospirida Dzik, 1983, regarding Hyperstrophina Linsley and Kier, 1984 as a junior synonym.

International audience; Sixty one core samples from three shallow core holes (Qusaiba-1, Baq'a-3 and Baq'a-4) penetrating the Qalibah Formation (Qusaiba Member) in the North Central Saudi Arabia were investigated. These core slabs corresponding to grey–greenish hemipelagic shale or silty-shale yield well-preserved and very abundant early Silurian chitinozoans. Most of the recorded chitinozoan assemblages are diverse and include several new species occurring with well-known species. An informal early Rhuddanian chitinozoan assemblage dominated by Cyathochitina caputoi is documented in the lowermost part of the Qusaiba Member. The six chitinozoan biozones defined above this basal assemblage range from Aeronian to Telychian. They are considered of regional value for northern Gondwana. From the lowest to the highest they are the Angochitina qusaibaensis (pro parte), Conochitina alargada, Angochitina hemeri, Angochitina macclurei, Tanuchitina obtusa and Euconochitina silurica biozones. The older regional biozones have been previously documented in Saudi Arabia whereas the two youngest ones, the eponymous index species of which were described from the subsurface of the Algerian Sahara, are documented for the first time in the Arabian Peninsula. Four subbiozones, of at least of regional application, are also defined in order to improve the precision of biostratigraphic correlation between Silurian lithostratigraphic units cropping out along the Arabian Shield and their counterparts in the subsurface of Central Saudi Arabia. Thanks to the closely spaced and to the regular sampling, the total range of several highly diagnostic forms as well as the interval of uncertainty between the successive chitinozoan biozones are better constrained. A hiatus with a duration of late Rhuddanian to early Aeronian separates the lowest informal chitinozoan assemblage from the qusaibaensis Biozone. A recent detailed study of the graptolites in the three cored holes provides independent chronostratigraphical control calibrating the previous chitinozoan-based age assignments. The qusaibaensis (pro parte), the alargada, and the hemeri chitinozoan biozones occur with the mid-Aeronian convolutus graptolite Biozone whereas the macclurei chitinozoan Biozone extends through the early Telychian guerichi and turriculatus graptolite biozones. The obtusa and the silurica chitinozoan biozones occur in an interval devoid of usable graptolites. They are referred to the mid–late Telychian as they do not contain typical Sheinwoodian species.Besides the abundant chitinozoans and acritarchs, sporadic occurrences of scolecodonts and of eurypterid cuticle fragments are also noted in the organic residues. The presence of eurypterids reflects a shallowing trend in the sedimentary record, which is consistent with the distribution of the graptolite remains (siculae and/or rhabdosomes). Indeed, graptolites are common throughout the Qusaiba Member, except in the youngest processed samples presaging the shallower environments prevalent in the Sharawra Member. The taphonomy of the chitinozoans (isolated vesicles, chain-like structures, clusters, coprolites) and their environmental context is briefly discussed.Fifteen new species are described and illustrated: Ancyrochitina alhajrii sp. nov., Ancyrochitina camilleae sp. nov., Armoricochitina crassicarinata sp. nov., Armoricochitina gengi sp. nov., Bursachitina baqaensis sp. nov., Conochitina viiuae sp. nov., Cutichitina minivelata sp. nov., Cyathochitina neolatipatagium sp. nov., Fungochitina merrelli sp. nov., Muscochitina olivieri sp. nov., Plectochitina alisawyiahensis sp. nov., Plectochitina alnaimi sp. nov., Plectochitina jaquelineae sp. nov., Plectochitina lucasi sp. nov., and Spinachitina geerti sp. nov.Keywords

International audience; A belemnite fauna collected in the lowermost Toarcian succession that crops out near Moulay Idriss (northern Morocco) is studied in this article. This is the first palaeontological study of Early Toarcian belemnites from Northern Africa, i.e., the northeastern margin of the Gondwana, in connexion with Tethys. Four species of the family Passaloteuthidae Naef, 1922, have been identified: Passaloteuthis bisulcata (de Blainville, 1827), Pseudohastites longiformis (Blake, 1876), Parapassaloteuthis zieteni (Mayer-Eymar, 1884) and Parapassaloteuthis sp. A. All species have been collected in lowermost Toarcian beds dated to the ammonite Polymorphum Chronozone (=Tenuicostatum Chronozone), which coincides with the belemnite Passaloteuthis bisulcata biozone. The discovery of a syntype of this zonal index is discussed. The identified species are common with Europe, thus suggesting that theonset of the belemnite provincialism in the Toarcian could post-date the earliest Toarcian Polymorphum—Tenuicostatum Chronozone. However, records of Early Jurassic belemnites are still too sparse to recognize the establishment of provincialism and the timing of its onset.

International audience; Remains of various fossil mammals were found within a large quarry close to Baixas village (E-Pyrénées Dept., France). Among them are tooth remains of a bat poorly known as a fossil: a rhinopomatid one.The presumed age of the associated fauna, especially obtained from the rodents, is recognized to be the MN 4 biozone (Early Miocene, about 16 My). The Rhinopoma Geoffroy Saint-Hilaire, 1818 genus is mostly known from the recent fauna, with rare species (two more common ones), extending across warm to arid areas of the Western Old World. Rare fossil rhinopomatids are reported, from Fayum (Egypt), Israël, and north-mediterranean egean Greece. The Baixas ones are 65 specimens. They display the typical tooth morphology of these bats, nevertheless preserving some structures which vanished from recent ones, or less evolved (as regards lower and upper canines, or P4). The originality of this rhinopomatid species supports its recognition as a new genus and species, Corbarhina handae n. gen., n. sp. Recent molecular considerations supported the rhinopomatids origin from rhinolophoid ancestry. The position here promoted from tooth morphology retains the rhinopomatid origin from emballonurid ancestors.

To improve the French Plio-Pleistocene biostratigraphy scheme based on mammal biozone boundaries or “Mammal Neogene/Quaternary Zones” (MNQ) we collected volcanic material that could be dated using the 40Ar/39Ar method in five exceptional mammalian paleofauna sites located in the Massif Central (France). We present 40Ar/39Ar ages that we obtained for Perrier-Les Etouaires, Roca-Neyra, Chilhac, Seneze and le Creux de Peyrolles. We show that the overall stratigraphic position of these sites based on faunal assemblages is valid from the relative point of view. However, we greatly improve both the accuracy and precision of the age of these mammalian paleofaunas. We obtained 40Ar/39Ar ages varying between 2.78 ± 0.01 Ma (1σ external) for Les Etouaires (Lower MNQ 16b) and 1.47 ± 0.01 Ma for the Creux de Peyrolles site (MNQ 19). Based on these new dates we estimate the duration of several biozones including MNQ 16b, 17a and 17b. We suggest that the first Late Villafranchian biozone (MNQ 18) starts as early as the Reunion subchron or just after. The first occurrence of Equus stenonis in Roca-Neyra (i.e. 2.60 ± 0.02 Ma) is close to or synchronous with the Gauss–Matuyama transition (i.e. 2.59 Ma) and the Pliocene/Pleistocene boundary. The chronological framework we build shows the very rapid increase of the large grazers community in French faunal assemblages at the beginning of MNQ 17 (i.e. 2.6 to 2.4 Ma). This rapid faunal turnover is probably associated with a general decrease of woodland habitat in the Massif Central contemporaneous with the onset of the Northern Hemisphere glaciations. The faunal assemblages in France, Spain, and Italy covering the period between 2.1 and 2.0 Ma suggest that favorable conditions for early hominin settlement (mainly savannah prairies, grassland with open forest patches) existed in southwestern Europe at least 200 ka before the first traces of Homo in Eurasia. This period also shows the arrival of taxa originating in Asia and Africa, suggesting dispersal events within southwestern Europe well before the Olduvai subchron and with no indication (as yet) of Homo as a “fellow traveler”.

International audience; This synthesis aims to integrate former, recent and unpublished data on fossil micromammals (Rodentia, Erinaceomorpha, Soricomorpha, Chiroptera) from Moroccan, Algerian and Tunisian archeological and paleontological sites. An updated biochronology of these taxa is established from the middle Miocene to the Holocene. Ten main biozones are defined: they are characterized by specific faunal assemblages, whose evolution and migrations were influenced by geologic and climatic events throughout the studied period. During the Miocene, Myocricetodontinaewere dominant. This period was followed by a progressive diversification among Murinae, Gerbillinae, and Crocidurinae from the Plio-Pleistocene onwards, along with sporadic occurrences of European, Asian and sub-Saharan taxa, before a decrease in small mammal diversity at the beginning of the late Pleistocene, while modern faunas stabilized. Overall, the newbiochronology matcheswellwith the former ones. However, some slight discrepancies emerge, notably because the former biochronologies were based on more sporadic data and often did not consider thewhole smallmammal faunas. The present work represents the first complete biochronological synthesis of North African small faunas for the whole late Cenozoic, which should be useful for paleontologists and archeologists in providing an up-to-date framework into which future discoveries will easily find their place.

The Archaeocyatha is a group of Cambrian fossils successively considered as cnidarians or sponges or as an independent phylum convergent with many groups lacking clear affinities. Comparisons with Recent calcified sponges discovered in submarine caves have demonstrated that the sponge model is consistent with their structural organization. Thus their systematic position is now agreed as a class within the phylum Porifera, permitting realistic investigations of their comparative physiology and life strategies. Archaeocyatha is an important part of research programmes on the Cambrian System, initiated by different commissions of the IUGS since 1970. Archaeocyathan biozones are available in some key regions. Faunal and palaeocommunities distribution, especially of the reefs they helped build in epeiric seas, and migration pathways constrain Cambrian palaeogeographical reconstructions. A database, using recent compilations of the group, is now online. This free access data source offers specialists a tool, easy to use not only as an identification key but also to establish faunal, geographical and stratigraphical distributions of archaeocyathan genera, and a rapid first step towards Cambrian palaeogeographical reconstructions.

Fluvio-lacustrine Holocene sequences from the semi-arid region of eastern Morocco are rich in shells and show similar sedimentary levels that could correspond to synchronous environmental variations. The high diversity of Moroccan continental malacofaunas makes them a very suitable fossil group for palaeoenvironmental reconstructions and palaeobiodiversity implications. The malacological study of Blirh is the first in Morocco to be based on a systematic sampling providing a complete faunal record in order to reconstruct palaeoenvironmental successions. Three biozones have been recognized. They illustrate occurrence of a marsh and a lake from shortly before 10,600 cal. BP followed by an abrupt drying up around 5000 cal. BP. This dramatic environmental change is not synchronous with lithological variations as stated by previous studies based on geological and palynological records. The Blirh lacustrine phase fits into the humid period that follows full glacial hyperarid conditions during the latest Pleistocene in North Africa from 14,800 cal. BP. The abrupt shift to dry conditions around 5000 cal. BP inferred from the malacological succession correlates with the contraction of Saharan lakes. During the last biozone, despite disappearance of the main water-body, marshy species persist and demonstrate occurrence of very wet environments in the Middle Moulouya plateau until historical times. Several species, currently absent from the region, were found within the Holocene assemblages. At least two new species of aquatic molluscs (Hydrobiidae) have been discovered. Sampling of modern malacofaunas from wells and springs in the area has demonstrated that one of them is still living in the water-table. The Blirh malacological record provides an insight of the palaeo-biogeographical changes affecting this group during the Holocene and demonstrates the very recent increase of human impact on the regional biodiversity.

12 pages; International audience; High-resolution gamma-ray measurements performed on five biostratigraphically well-dated reference sections from the Vocontian Basin (south-eastern France) are used to develop a new astrochronology of the Valanginian Stage and its subdivisions (i.e. ammonite and calcareous nannofossil zones and subzones). Spectral analyses show a pervasive dominance of 405-kyr eccentricity cycles with the expression of 100-kyr eccentricity, obliquity and precession. Previous rough estimates of Valanginian Stage duration ranged from 3.9 to 6.5 myr but were generally based on less reliable or indirect methods. This study provides a precise duration of 5.08 myr, tuning the series to the 405-kyr eccentricity cycle, thus further enhancing the accuracy of the Geologic Time Scale. New durations of magnetochrons are proposed based on intercalibration between ammonite and calcareous nannofossil biozones, cyclostratigraphy and carbon-isotope stratigraphy. After integrating orbitally calibrated durations and available radio-isotopic ages for the Berriasian-Hauterivian interval, a link between theWeissert Event and the emplacement of the Paraná-Etendeka Traps now appears unlikely. Strontium, carbon and oxygen isotope stratigraphy, sedimentological and palaeontological features, clay mineralogy, and the orbital record during the Upper Valanginian all suggest that a transient cool, arid climate occurred after the carbon isotope event, possibly associated with limited polar ice.

This work deals with the study of the ammonoid record of a classical stratigraphic section of Aptian age, the Francisco Zarco Dam (Durango State, northeast Mexico). A detailed biostratigraphical analysis considered 1281 specimens systematically sampled on a bed-by-bed basis. Taphonomy, taxonomic composition and paleocology of the studied assemblage, were also stressed. We formally propose an ammonite zonation for this section, which consists of two interval zones, Dufrenoyia justinae and Gargasiceras? adkinsi, one taxon range zone Caseyella aguilerae, and one biohorizon Huastecoceras trispinosoides. Among those biostratigraphic units, three are of new definition. Another topic discussed herein concerns to the problematic definition of the Lower-Upper Aptian boundary using the first stratigraphical appearance of the genus Epicheloniceras. From a paleoecological point of view, we recognized the ammonoid assemblage of the Francisco Zarco Dam section, to be representative of a distal platform environment. Finally, we compared the zonation built for this section with that considered the standard zonation for the Tethyan Domain, concluding that the differences are so substantial that an independent zonation for the Central Atlantic is necessary.

10 pages; International audience; An orbital floating time scale of the HauterivianeBarremian transition (Early Cretaceous) is proposed using high-resolution magnetic susceptibility measurements. Orbital tuning was performed on the Río Argos section (southeast Spain), the candidate for a Global boundary Stratotype Section and Point (GSSP) for the HauterivianeBarremian transition. Spectral analyses of MS variations, coupled with the frequency ratio method, allow the recognition of precession, obliquity and eccentricity frequency bands. Orbitallytuned magnetic susceptibility provides minimum durations for ammonite biozones. The durations of well-constrained ammonite zones are assessed at 0.78 myr for Pseudothurmannia ohmi (Late Hauterivian) and 0.57 myr for Taveraidiscus hugii (Early Barremian). These results are consistent with previous estimates from the other reference section (Angles, southeast France) and tend to show that the Río Argos section displays a complete succession for this time interval. They differ significantly from those proposed in the Geologic Time Scale 2008 and may help to improve the next compilation. The Faraoni Oceanic Anoxic Event, a key Early Cretaceous oceanographic perturbation occurring at the P. ohmi/P. catulloi subzone boundary has a duration estimated at 0.10-0.15 myr, which is similar to previous assessments.

International audience; This study illustrates bathymetric trends across the northern Gondwana platform during the Ordovician. The sedimentary records of the Algerian Sahara, central Morocco, and western France are investigated to document related environmental changes through the period. Outcrop and subcrop sections have been selected with regard to their completeness and to the precision of the available biostratigraphical data, based on chitinozoans. This group provides the most continuous biostratigraphical record in the terrigenous Ordovician successions of northern Gondwana. For each area, the chitinozoan data have been assembled, updated and referred to one of the 26 Ordovician chitinozoan biozones defined in northern Gondwana regions. A sequential analysis based on the identification of genetic units is presented. The stacking pattern of these units is established for each locality, and the resulting curves express variations in sedimentary environments partly driven by relative sea-level changes. From successive smoothings of these curves, we define 16 main cycles at lower frequencies. Uncertainties concerning the precise chronostratigraphic position of some of these cycles are discussed. The proposed northern Gondwana relative sea-level variation curves are compared to the recently-published global Ordovician sea-level curve and to other regional curves available for the major Ordovician palaeoplates (Laurentia, Baltica, South China, north-eastern Gondwana).

Late Carbonifeous to Permian core samples from two borehole sections, STRAT 1 and CKP 6, that penetrate the glacial to postglacial and coal-bearing Lower Karoo sequence, Kalahari Karoo Basin, Botswana, contain well preserved pollen and spore palynomorphs. The palynomorph assemblages comprise 165 species of spores and pollen, and few acritarchs and chlorophycean algae. This paper presents a local biozonation of three succeeding assemblage zones, recognisable in each borehole section. The assemblage zones are named: the Hamiapollenites bullaeformis Biozone, the Cyclogranisporites gondwanensis Biozone and the Platysaccus papilionis–Striatopodocarpites fusus Biozone, in ascending order of stratigraphy. Assemblages are compared and correlated with assemblages described from other Gondwana areas of Africa, Australia, Arabia, South America and Antarctica. A general analysis of taxa from the Kalahari Karoo Basin indicates a distinct similarity with assemblages from the Paraná Basin of South America. The Hamiapollenites bullaeformis Biozone is comparable with the Vittatina costabilis Interval Zone of the Paraná Basin. Assemblages from the Cyclogranisporites gondwanensis and the Platysaccus papilionis–Striatopodocarpites fusus zones are comparable with the Lueckisporites virkkiae Interval Zone. Age determination for the assemblages in the Kalahari Karoo Basin is inferred from comparison with similar assemblages from previous Gondwana studies, and ranges from the Late Carboniferous (Kasimovian–Gzhelian) to latest Early or possibly earliest Middle Permian (Late Cisularian to Early Guadalupian). • Key words: Kalahari Karoo Basin, Late Carboniferous–Permian, pollen, spores, assemblage zones.

Meteoric diagenesis of Upper Cretaceous and Paleocene-Eocene shallow-water carbonates in the Kruja Platform (Albania): geochemical evidenceIn the central part of the Kruja Platform (Albania) located in the Apulian passive margin, geochemical analyses (calcimetry, Sr, REE and isotopic, δ13C and δ18O) coupled with sedimentological and sequence stratigraphic study were carried out on Upper Cretaceous (CsB4, CsB5, CsB6 Biozones) and Paleocene to Middle Eocene shallow-water carbonates that crop out in the Kruje-Dajt massif (L'Escalier section) and Makareshi massif (La Route section). The lower values in Sr contents, the homogeneous δ18O values in both sections and the covariance between δ13C and δ18O values (La Route section) are attributed to diagenesis influence by a meteoric water-buffer system, supported by petrographic observations. Moreover, a new exposure surface during the Late Cretaceous time (between CsB5 and CsB6 Biozones) may be proposed according to the low or negative excursions of Sr values, the negative excursions of isotopic values in both sections and a positive peak of normalized REE values (La Route section). These variations correlate with the geochemical signal reported by the decreasing strontium isotope values of rudist shells in the Island of Brač carbonate platform (Apulia domain) during the late Middle Campanian (77.3 Ma). Also, this continental exposure is consistent with the global sea-level fall reported from the Boreal Realm, North Atlantic, and the southern Tethyan margin. This geochemical evidence is a complementary tool for the sedimentological analysis and suggests a maximum regression (a sea-level fall) at the transition between the CsB5 and CsB6 Biozones. The high values of Sr content in Middle Eocene carbonates (L'Escalier section) reflect changes in depositional environment from restricted to open marine conditions. REE values increase through transgressive systems tract, characterized by small increase of detrital input. However, anomalies of certain values in both sections suggest disturbances linked either to the changes in clay input and to diagenetic modifications. Peaks in dolomite content are linked with regressive episodes or tendencies, and dolomitic facies, as indicated by intertidal-supratidal depositional environments.

A detailed study of chitinozoans based on a systematic bed-by-bed sampling of the Dawan Formation was carried out in the Yichang area (West Hubei, China) on two representative sections located at Chenjiahe and at Huanghuachang, where the GSSP of the base of the Dapingian (i.e. the base of the Middle Ordovician) has been defined. Four chitinozoan zones, in ascending order the Conochitina raymondii biozone, the Conochitina langei biozone including the Lagenochitina lata and the Conochitina pseudocarinata sub-biozones , the Lagenochitina combazi biozone, and the Sagenachitina dapingensis biozone, are recognized in the Dawan Formation, which ranges in age from the Floian to the early Darriwilian. In both sections the chitinozoan biozones benefit from a direct calibration with conodont and graptolite biozones. The base of the Lagenochitina combazi biozone is very close, or coincides with, the base of the Dapingian, as defined by the FAD of the conodont B . triangularis. For global correlation purposes three important Ordovician chitinozoan genera, i.e. Belonechitina, Sagenachitina and Cyathochitina have their FAD in the Dapingian. A total of 8 genera and 29 species, including 3 new species ( Sagenachitina dapingensis sp. nov., Tanuchitina huanghuaensis sp. nov. and Lagenochitina yilingensis sp. nov.), are described and figured in this paper.

12 pages; International audience; Magnetic susceptibility (MS) variations record Earth's orbital parameters in the clays and marls of the Early Oxfordian in the Paris and Vocontian basins of France. Climatically driven weathering of surrounding emergent areas and the resulting detrital input to the basins is a significant source of the MS signal. MS proves to be an effective tool for deciphering the orbital forcing signal in these sediments, and for assessing the chronology of these formations. The 405-kyr orbital eccentricity cycle is clearly visible in the MS signal and, consequently, is a valuable geochronometer for this portion of the Jurassic time scale. Astronomical calibration of the Mariae ammonite zone (basal Oxfordian stage) indicates a duration of ~2.2 myrs, whereas current time scales assign only 0.6 myrs to this biozone. However, the Late Jurassic time scale has large uncertainties in stage boundary ages (±4 myrs), hence of interval durations. These results could lead to significant revisions in the M-sequence magnetic anomaly block model, and greatly improve the resolution of the Jurassic time scale.

The Upper Aptian-Lower Albian Mural Formation of the Bisbee Group in northern Sonora consists of eight members, in ascending order the Fronteras, Rancho Bufalo, Cerro La Ceja, Tuape Shale, Los Coyotes, Cerro La Puerta Shale, Cerro La Espina and Mesa Quemada. These members represent shallow marine facies of a major marine transgressive-regressive event that reached the Bisbee basin, except for the Rancho Bufalo Member which is a tongue of the fluvial Morita Formation that underlies the Mural Formation. The facies, succession and regional correlation of its members indicate that deposition of the Mural Formation occurred in northern Sonora on a broad carbonate shelf, the Sonoran shelf, where depositional environments varied from restricted shelf with local terrigenous deltaic and fluvial influence to open shelf with coral-rudist buildups, to offshore shelf. Facies of the Mural deepen across eastern Sonora into the Chihuahua trough and the formation pinches out northwestward in Sonora. The Sonoran shelf was flooded by three long-term depositional cycles of approximately 2.5 myr duration. The first cycle deposited the Fronteras and Rancho Bufalo members and is older than 115.5 Ma, about 118 Ma. The marginal to shallow marine deposits of the Fronteras Members disconformably overlie fluvial strata of the Morita Formation and are sharply overlain by fluvial deposits of the Rancho Bufalo Member. The second cycle deposited the Cerro La Ceja, Tuape Shale and Los Coyotes members and probably embraces the Aptian/Albian boundary; the Cerro La Ceja Member disconformably overlies the Rancho Bufalo Member and Morita Formation in northeastern Sonora but gradationally overlies the Morita in the sections of north-central Sonora. The third cycle deposited the Cerro la Puerta Shale, Cerro la Espina and Mesa Quemada members and is Early Albian in age. The Mesa Quemada Member is gradationally overlain by fluvial deposits of the Cintura Formation. Biostratigraphy is based on ammonites, bivalves, gastropods, benthic and planktic foraminifers, and colomiellids and two biozones are erected to correlate the measured sections.

Chitinozoans collected from upper Tremadocian to lower Floian strata of Chenjiahe section, Yichang, western Hubei, China comprise six species belonging respectively to the genera Euconochitina including a new species, Euconochitina fenxiangensis, Lagenochitina and Bursachitina, together with Desmochitina sp. and Eremochitina sp. The chitinozoan succession across the interval is correlated with relevant conodont and chitinozoan biozones and two new regional chitinozoan biozones, the Lagenochitina destombesi Biozone and the Euconochitina symmetrica Biozone are proposed based on their stratigraphic ranges in the Fenxiang to Honghuayuan formations in the Chenjiahe section.

13 pages; International audience; The ammonite genus Alocolytoceras Hyatt, 1900 is an uncommon lytoceratid with distinctive shell ornament. A set of 58 specimens, recently collected at Amellago in the central High Atlas (Morocco), has enabled us to trace a succession of three species over eight biozones from the Toarcian to the Aalenian. Two specimens from the Lusitanian Basin are added for comparison. Following a review of the genus, based on original specimens and data from the literature, seven species are considered valid. A palaeobiogeographical synthesis of 13 regions demonstrates irregular distribution patterns over time, with a constant presence in the south-west Tethys and an instance of rapid diversification of an endemic fauna in north-west Europe. Our data challenge the conventional view that lytoceratid ammonite evolution was ‘conservative'.

The oldest assumed ostracods appear in the fossil record from the Tremadocian Paltodus deltifer conodont Biozone. Although geographically widespread these early ostracods have no obvious Cambrian antecedents. Their first appearance at ca. 485 Ma contrasts with molecular evidence that suggests a much earlier (latest Proterozoic or Cambrian) origin for ostracods. Some Cambrian bivalved arthropods such as Altajanella and Vojbokalina, conventionally referred to the Bradoriida, have carapace morphologies that resemble Ordovician palaeocopid ostracods, though such a relationship is unproven without soft part anatomy. Evidence from preserved soft anatomy demonstrates that Bradoriida, such as Kunmingella, and Phosphatocopida, essentially the Cambrian 'ostracod' record of traditional usage, belong outside the Eucrustacea. Early Ordovician ostracods appeared first in shallow marine, oxygenated environments on shelf margins, in a similar setting to other elements of the 'Paleozoic fauna'. Their biodiversity was low (3 named genera and ca. 12 species), though some taxa such as Nanopsis and Eopilla achieved widespread dispersal between major Ordovician palaeocontinents. As bradoriids were largely extinct by the Late Cambrian, ostracods do not appear to have directly competed with them for shallow marine environments. The rapid colonisation of these settings by ostracods may have been facilitated by the available ecospace vacated by Bradoriida.

Thirty-five radiolarian species, belonging to two assemblages, one from the Changhsingian and the second one from the early Anisian, were recovered from siliceous rocks occurring in Xijirulan orogenic belt, northern Tibet. A new radiolarian species of them, Cryptostephanidium tibetensis, is described. The lower Anisian Eptingium nakasekoi assemblage co-occurs with conodonts belonging to Chiosella timorensis Zone. This fact allows correlation between radiolarian and conodont biozones. The lower Anisian radiolarian assemblage has a high diversity and supports that radiolarian radiation after the end-Permian mass extinction begins in the earliest Anisian. The research on the lithostratigraphic sequence and sedimentology shows that the old land of the Xijirulan orogenic belt, formed by the collision between the Qiangtang and Koh Xil terranes at the latest Early Permian, has disappeared in the early Changhsingian. During the Changhsingian and Triassic, the Xijirulan orogenic belt has become a deep marine basin and was combined with the Bayan Har Basin. This large deep sea basin extended until the end of the Triassic, locally possibly until the Jurassic.

International audience; In the Albian to Coniacian subsurface series of Jaisalmer Basin, Rajasthan, India, the distribution of ostracode assemblages is proposed, calibrated using planktonic foraminifera biozones of the global standard stages. Ninety species, 19 named and 71 in open nomenclature, belonging to 45 known genera and one unknown, are indexed; their first and last appearance (or first and last observation)levels, compared with the stage boundaries, are used as biostratigraphical guide markers. The ostracode assemblages enable us to recognize and define the Cenomanian, Turonian and Coniacian stages. Cenomanian-Turonian faunistic communications appear between the Jaisalmer Basin and different countries of the southern Tethyan margins and the eastern and western Atlantic borderlands.

Revision of the lithostratigraphy of Ordovician deposits in southern and southeastern Turkey led to a re-evaluation of the age assignments of formations identified in the subsurface and at outcrop. Previous datings were based on macrofauna (mainly trilobites and graptolites). The present paper focuses exclusively on organic-walled microfossils (chitinozoans and acritarchs), which provide numerous chronostratigraphical improvements, especially in successions barren or poor in macrofossils. Close to 200 samples were collected in the Taurus chain (i.e. from Kemer, Seydisehir, Ovacik, Kozan, to Sariz regions in southern Turkey) and in the Border Folds (Mardin and Hakkari regions), usually regarded as part of the Arabian Plate in palaeogeographical reconstructions. Many samples are productive and yield chitinozoans and/or acritarchs of extremely variable preservation, depending on their geographical and geological location. In the Taurus chain, the material is “coalified” and frequently fragmented whereas, in the Border Folds, maturation of the organic matter is much lower and preservation of the microfossils is good to excellent. Several Ordovician chitinozoan biozones (northern Gondwana zonation) as well as diagnostic acritarch assemblages are identified in southern and southeastern Turkey. These Ordovician formations are assigned here to the new global stages of the Ordovician chronostratigraphical scale. The Seydisehir (upper part), Sobova, and Kilgen Lake (lower part) formations are referred to the Darriwilian. The Kilgen Lake (upper part), Sort Tepe, and Bedinan formations are attributed to the Sandbian and to the Katian, and the Halevikdere Formation (glacio-marine part) is assigned to the Hirnantian. Reworking of Early Ordovician acritarchs is documented in pre-glacial and in glacial Late Ordovician deposits. They indicate that active erosive processes occurred during the Middle and Late Ordovician sedimentation. The organic-walled microfossils recorded in the Ordovician of south and southeastern Turkey belong to the northern Gondwana realm. Interestingly however, some Baltoscandian influences are noted in the Border Folds during Early Late Ordovician.

International audience; Subfossil chironomid assemblages spanning the last Interglacial/Glacial transition at Les Échets (France) highlight the environmental and climatic changes that took place at this crucial period. The Early Eemian warming is marked by increased percentages of warmwater taxa and decreased percentages of coldwater taxa. In the Middle Eemian, a lowering in water level is indicated by a rise of littoral taxa. In the Late Eemian, chironomids indicate anoxic deep waters and rise of water level, probably induced by increased rainfall. Mélisey I and II and the beginning of the glacial period are marked by the reappearance of coldwater taxa, lower percentages of warmwater taxa, and dominance of littoral taxa, probably correlated with lower water level and climate aridity. St Germain I and II are marked by higher percentages of warmwater taxa, lower percentages, or absence of both coldwater and littoral taxa.

International audience; One of the significant results of the multidisciplinary investigations carried out during recent years in the Lower Aptian historical stratotype of the Cassis-La Bédoule region (South-Eastern France) was a proposal to update the local Upper Barremian/Lower Aptian ammonite biozonation in order to be more consistent with the standard Mediterranean zonal subdivisions. So the lower and upper boundaries of the Lower Aptian (= Bedoulian substage of most French authors) as well as the boundaries of four biozones (Paradeshayesites tuarkyricus, P. weissi, Deshayesites deshayesi, Dufrenoyia furcata zones) and two subzones (Roloboceras hambrovi and Paradeshayesites grandis subzones) were identified and formally defined in the stratotype. However, to support this zonal scheme additional descriptions and illustrations of the ammonites collected bed by bed in the several sections studied were still required. In this paper we describe the members of the most significant ammonite family found in the Lower Aptian of Cassis-La Bédoule, i.e. the Deshayesitidae, and delimit precisely their stratigraphic positions. As regards zonation, we have replaced the index ammonite of the earliest Bedoulian Zone, i.e. Paradeshayesites tuarkyricus (Bogdanova, 1983), by Paradeshayesites oglanlensis (Bogdanova, 1983), and re-established the Pseudocrioceras waagenoides Zone as a subzone.

Our stratigraphic time scale was built during the XIXth century by West-European geologists from their knowledge of Western Europe. The result could have been very different. Trias came from the superposition of three formations in Germany. Eocene, Pliocene: Lyell's divisions of the Tertiary Era, according to the proportion of present genus or species in the catalogues of faunas. D'Orbigny invented the stage when Oppel defined the zone (our biozone). During the XXth century? Impact of oil prospection: boreholes, well-loggings, micropaleontology, economic competition. Access to the oceanic domain. Numbering the duration. Attempts towards a worldwide understanding beyond the diversity of languages and customs: colloquiums, stratigraphic codes or guides. Finally, from description, stratigraphy trends towards explanation: genetic stratigraphy. Stratigraphy today? A tool in attendance on the various branches of Earth sciences, to assign a place to their information within its time scale., Notre échelle stratigraphique, construite au long du XIXe siècle par des géologues ouesteuropéens à partir de la géologie continentale de l'Europe occidentale, aurait pu être tout autre. Elle a dépendu des hommes, des circonstances. Le Trias : c'est l'empilement de trois ensembles d'Allemagne. Éocène, Pliocène : découpage par Lyell d'après la proportion de formes actuelles dans les inventaires de faunes tertiaires... D'Orbigny invente l'étage alors qu'Oppel définit la zone. Au XXe siècle ? Impact de la prospection pétrolière : forages, diagraphies, micropaléontologie, concurrence. Accès au domaine océanique. Chiffrage de la durée. Mondialisation, il faut s'entendre par-delà la diversité des langues, des conceptions : colloques, codes, guide... Enfin, de descriptive, la stratigraphie se veut explicative : stratigraphie " génétique ". La stratigraphie aujourd'hui ? Un outil au service des diverses branches de la géologie, auxquelles elle donne le cadre-temps où situer toutes leurs informations.

In a context of convergence between Africa and Europe, the western Mediterranean domain is characterized by the opening of the Liguro-Provençal ocean in the early Miocene and of the Tyrrhenian Sea since the middle Miocene. These openings are preceded by an Oligocene rifting episod. New biostratigraphic, geochronologic and paleomagnetic data allow to propose an integrated stratigraphy sketch for the Oligo-Miocene period in Corsica. The continental syn-rift deposits, in the region of Ajaccio, have been dated as late Chattian from the presence of a mammal, Pomelomeryx boulangeri. Their paleomagnetic study indicates an anticlockwise rotation of 44 ±4° with regard to the stable Europe. The early Miocene succession was deposited on a contrasted topography inherited from the Oligocene glyptogenesis period. The lowermost Miocene deposits are represented by 4 pyroclastic flow deposits in southern Corsica. New 40Ar-39Ar datings on plagioclase concentrates give ages between 21.3 and 20.6 Ma (late Aquitanian). Paleomagnetic directions indicates that the rotation of Corsica had probably begun at this time. The Miocene marine sediments of the Bonifacio basin are divided in two formations. At the base, the Cala di Labra formation, that comprises 3 reef formations in coastal onlap (R1, R2, R3), is attributable to the Globigerinoides trilobus zone. In the environment of R1, miogypsin population includes mainly Miogypsina intermedia with a few M. globulina and M. cushmani. The absence of the less evolved forms (10 < V < 35) let us suppose that at least the lower Burdigalian is absent at Bonifacio because the region was emerged. R2 reef has a similar population (42 < V < 70), which suggests a rather short interval of time between the two stages of reef construction. On the other hand the R3 population contains only evolved forms (M. mediterranea) suggesting a late Burdigalian age. The end of the sedimentary succession (Bonifacio formation) is essentially represented by a pile of hydraulic dunes. The absence of Orbulina shows that this upper unit is older than late Langhian (biozone N9). Miocene sediments from Saint-Florent are divided into 3 marine formations bracketed by two continental ones. At the base, the continental formation of Fium’Albinu (equivalent to the Cala di Labra formation) is surmounted by the Torra formation attributed to Late Burdigalian based on the presence of G. trilobus and G. bisphericus. The Sant’Angelo formation (equivalent to the Bonifacio formation) developed from latest Burdigalian to late Langhian. The Farinole formation represents early Serravallian (base of the Globoquadrina altispira altispira zone). Despite the large number of studied sites in this study and others, the only reliable Oligo-Miocene paleomagnetic results in Corsica are the following ones : – the Vazzio formation indicates a rotation of 44 ± 4° after the late Oligocene, – the southern volcanic flows show that the rotation was in progress around 20.7 Ma (late Aquitanian), – the Fium’Albinu formation indicates a rotation of 30 ± 12° after early Burdigalian, – site B from Vigliotti and Kent [1990] gives a rotation of about 11 ± 5° after early Langhian. Our paleomagnetic data, together with the existing ones, associated to the biostratigraphic and geochronologic ages show that the opening of the Ligurian basin coincides with an anticlockwise rotation of 45° of Corsica, which begins between 23 and 21 Ma and ends around 15 Ma. This is in agreement with the idea of Sardinia and Corsica rotating as a single almost rigid block during Miocene times.

Two new forms of Pristiograptus dubius, here designated as varieties "A" and "B", are described and figured. Both were found in core samples representing the perneri through lundgreni biozones of the Wenlock epoch. The cores are from boreholes Šiupyliai-69, Parovéja-9, Likénai-396, Paežeriai-222 and Sutkai-87 in central and northern Lithuania. The associated graptolites Cyrtograptus perneri BOUCEK, C. radians TÖRNQUIST, C. lundgreni TULLBERG, Monograptus flemingii flemingii (SALTER), M. testis testis (BARRANDE), Monoclimacis flumendosae (GORTANI) and Pristiograptus pseudodubius (BOUCEK) (= P. parvus) are all indicative of the perneri, radians and lundgreni biozones of the Wenlock. Two species of Pristiograptus occur in this time-stratigraphic interval: P. dubius and P. lodenicensis. In P. dubius the degree and manner of extension of the thecal apertural lip (thecal hood) onto the succeeding theca distinguish it from otherwise very similar taxa. The thecal morphology of P. lodenicensis differs from that of a typical Pristiograptus in that the apertural lip has a central depression and is rounded into small lobes laterally. Résumé : Pristiograptus (Graptoloidea) des biozones à perneri, radians et lundgreni (Silurien) de Lithuanie. ––– Deux formes nouvelles de Pristiograptus dubius, appelées ici variétés "A" et "B", sont décrites et illustrées. Toutes deux ont été découvertes dans des échantillons de carottes dans un intervalle rapporté aux biozones à perneri, radians et lundgreni du Wenlock. Les carottes proviennent des forages Šiupyliai-69, Parovéja-9, Likénai-396, Paežeriai-222 et Sutkai-87 de Lithuanie centrale et septentrionale. Les graptolites rencontrés en association : Cyrtograptus perneri BOUCEK, C. radians TÖRNQUIST, C. lundgreni TULLBERG, Monograptus flemingii flemingii (SALTER), M. testis testis (BARRANDE), Monoclimacis flumendosae (GORTANI) et Pristiograptus pseudodubius (BOUCEK) (= P. parvus), sont tous caractéristiques des biozones à perneri, radians et lundgreni du Wenlock. Deux espèces de Pristiograptus sont connues dans cet intervalle stratigraphique : P. dubius et P. lodenicensis. Chez P. dubius le développement (importance et morphologie) des lèvres aperturales des thèques le long du rhabdosome permet de le distinguer d'autres taxons autrement très voisins. La morphologie des thèques chez P. lodenicensis est distincte de celle d'un Pristiograptus typique dans la mesure où la lèvre aperturale présente une dépression médiane et s'arrondit latéralement en petits lobes.

International audience; Chironomid assemblages were studied in Lake Lautrey (Jura, France) along a 2.50 m long core spanning the whole Lateglacial period. A stratigraphical constraint cluster analysis showed 7 biozones and 13 sub-biozones within the chironomid biostratigraphy. Characteristic taxa were allocated to each of the 7 biozones by simple analysis of the relative abundance diagram whereas several Correspondence Analyses (C.A.) were needed for the remaining 13 sub-biozones. Characteristic taxon compositions were interpreted using available quantitative inference models for total phosphorus concentration ([T.P.]), chlorophyll-a concentration ([Ch1-a]), hypolimnetic oxygen conditions, and water temperature. Optimum ranks of the characteristic taxa against the environmental factors provided by these inference models were used to deduce an evaluation of environmental conditions. Paleoenvironmental interpretations of chironomid assemblage changes showed the Lateglacial climatic event succession (Oldest Dryas, Bølling/Allerød Interstadial, and Younger Dryas) commonly recognized in the area. Moreover, a bipartition of the Oldest Dryas, the occurrence of two minor oscillations during the Bølling/Allerød Interstadial and a trend in environmental changes (climatic improvement) during the Younger Dryas were also found.

The review of the Cretaceous–Paleogene interval deposits of the Elles section based on a detailed sampling gives a good characterization of the K/T boundary and reconstitution of the geological events underlining this boundary. Thus, the discovery of a thin Ir-rich layer, with Ni and Cr-rich spinel and shocked quartz is a well preserved record of the known cosmic event that occurred at that time. This sudden event is also corroborated by the quantitative and qualitative organic components distribution along the K/T interval. Added to some other long-term events (e.g. climatic, eustatic), it generated a mass extinction, at the K/T boundary, of specialists among the Globotruncanids and Heterohelicids planktic foraminifera species. Following this biological crisis, the biotic turnover into the Danian is slow. The underlining of all the Cretaceous–Tertiary interval biozones attests that the Elles section is complete. If compared to the K/T stratotype and El Kef II sections, the Elles section is found to display a better exposure of the K/T interval and shows more expanded zones and subzones. Such characteristics promote the Elles section to be considered as a parastratotype.

In order to detect whether the end-Frasnian worldwide biotic crisis is related to an extraterrestrial impact, the global stratotype section of the Frasnian–Famennian boundary and auxiliary sections within the stratotype area have been examined for impact indicators: iridium, Ni-rich spinel bearing spherules and glassy microtektites. This area is particularly well suited to the search for discrete events because it exhibits biostratigraphically continuous sections of sedimentologically homogenous off-shore deposits. Different environmental settings on oxygenated deep-water seamounts, such as the stratotype section at Coumiac, and in oxygen-depleted depressions (La Serre section) are available. The latter is investigated in more detail because it is the least condensed across the boundary, which is determined by the first occurrence of the typical morphotype of Palmatolepis triangularis , the indicator of the first Famennian conodont biozone. Samples from the biostratigraphically defined boundary and adjacent levels failed to provide significantly high Ir values and no Ni-rich spinel or microtektite has been recovered. This is in contradiction with the results of earlier investigations carried out by H. Geldsetzer on the same section. In contrast, the values of Ir concentrations that we measured are always very low or not detectable. The small overabundances observed in some samples, which are about two orders of magnitude lower than what is currently observed at the Cretaceous–Tertiary boundary, are probably due to the accumulation of the normal flux of cosmic dust during periods of relatively low depositional rates or to a terrestrial origin. At present, we have no evidence that an extraterrestrial impact occurred at the F–F transition.