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Vianey-Liaud, Monique, Vidalenc, Dominique, Orliac, Maëva J., Maugoust, Jacob, Lézin, Carine, Pélissié, Thierry (2022): Rongeurs de la localité éocène de Cos (Tarn-et-Garonne, Quercy, France). Comparaison avec les rongeurs de localités de la transition Éocène inférieur/Éocène moyen. Geodiversitas 44 (26): 753-800, DOI: 10.5252/geodiversitas2022v44a26

Le site du Centre mobilisateur 10, situe au sud-est de l’agglomeration de Lannemezan (Hautes-Pyrenees) et autrefois connu sous le nom de l’Arsenal, a fait l’objet en 2016 d’une fouille preventive realisee par le bureau d’etudes Eveha, sous la responsabilite de V. Ropiot. D’un point de vue geographique, entre la Bigorre et le Comminges, ce secteur occupe une position d’interface sur un plateau de formation fluvio-glaciaire, qui culmine a 600 m d’altitude en piemont des Pyrenees, et qui constitue une vaste etendue comprenant des landes, des tourbieres, des prairies et quelques bois. La fouille, en plus du degagement complet d’un tumulus circulaire dote d’un enclos de galets, principal objet de cette intervention, a permis la mise au jour de dix structures archeologiques, dont un monument megalithique de conception singuliere, compose d’une dalle monolithe entouree d’une bordure de galets, recouvrant une chambre enfouie au sein d’une vaste fosse oblongue, comportant une entree frontale comprise egalement dans l’excavation.Les autres structures sont six foyers a galets chauffes, deux trous de poteaux isoles et une fosse contenant du mobilier du Bronze moyen, pillee ou fortement remaniee mais vraisemblablement de nature cultuelle. Le tout se developpe principalement dans la partie centrale de la zone prescrite, autour du tumulus, et vers l’est pour ce qui est des foyers, dont deux ont ete amenages dans sa couronne. Ces vestiges s’echelonnent sur une periode comprise entre 3700 et 1400 av. n.e., l’occupation etant centree sur le Neolithique final. Ils forment un ensemble funeraire monumental jusque-la inedit dans les Hautes-Pyrenees.

A rescue excavation at the site of Centre mobilisateur 10, located in the south-east of the Lannemezan agglomeration (Hautes-Pyrenees) and otherwise known as the Arsenal, was carried out in 2016 by the Eveha team, under the leadership of V. Ropiot. From a geographic perspective, this sector, between Bigorre and Comminges, occupies an interface position on a fluvio-glacially formed plateau, culminating at an altitude of 600 m at the foothill of the Pyrenees, and forms a vast expanse of land including heaths, bogs, meadows and some woodland.The excavation completely uncovered a circular tumulus with a pebble enclosure, which was the main aim of the operation. However, it also brought to light ten archaeological structures, including a singular megalithic monument, composed of a monolithic slab surrounded by a pebble border, covering a chamber buried in a vast oblong pit, with a frontal entrance.The other structures consist of six fireplaces with heated pebbles, two isolated post holes and a pit containing middle Bronze Age objects, which were plundered or heavily reworked but appear to be linked to worship rituals. All these structures are located in the central part of the excavated zone, around the tumulus, and towards the east for the hearths, including two developed in the crown of the tumulus. These remains are attributed to a period ranging from 3700 to 1400 BCE, centred around the Final Neolithic 2. They form an unprecedented monumental funerary complex in the High-Pyrenees.

International audience; The Groupe Français du Crétacé and GroupeFrançais d’étude du Jurassique are pleased to joinand offer this thematic issue as a tribute to ourcolleague and friend, Professor Jacques Rey, for hisremarkable career as a specialist of stratigraphy.Jacques Rey was a pioneer in Sequence Stratigraphy.Jacques Rey passed away at home, in Toulouse, onMarch 5th, 2018. He had carried out his academic careerat Paul Sabatier University of Toulouse. He beganas a teacher in 1962 until he retired in 2002. Duringthese forty years, he successively passed all academicdegrees: laboratory assistant (1964), assistantlecturer (1967), lecturer (1975) and professor (1979), jumping up to the exceptional level (1993). Since2002, he was professor emeritus.

International audience; Abstract The Toarcian Oceanic Anoxic Event (T-OAE) is marked by major palaeoenvironmental and palaeoceanographical changes on a global scale, associated with a severe disturbance of the global carbon cycle and organic-rich facies deposition. Here, a multiproxy approach (petrographic and geochemical techniques) was applied to the study of the organic content of the T-OAE of the Paris Basin, whose phytoplanktonic origin has been previously inferred by its geochemical signature. The top of the tenuicostatum Zone is characterized by palynomorphs and marine phytoplankton-derived amorphous organic matter (AOM), representing a proximal marine environment with emplacement of euxinic conditions at the top (total organic carbon/sulfur content and increase in AOM). At the base of the serpentinum Zone the proliferation of bacterial biomass begins, with phytoplankton playing a secondary role. This indicates the development of stagnant and restrictive conditions in a proximal environment, with water column stratification (neohop-13(18)-ene). The majority of the serpentinum Zone is dominated by bacterial biomass, suggesting a marine environment with bottom-water stagnation, possibly related to basin palaeogeomorphology and circulation patterns, with episodic euxinia. This therefore suggests that the T-OAE organic fraction is dominated by bacterial biomass, not phytoplankton, showing the importance of an integrated approach to the determination of the organic facies.

The Cenomanian—Turonian boundary is marked by one of the warmest periods of the Mesozoic, associated with high pCO2 levels and global sea-level highstands. Coupled to these extreme conditions is a massive magmatic episode, the establishment of worldwide marine anoxia, the deposition of organic-rich facies, and perturbations of the global carbon cycle, the so-called Oceanic Anoxic Event 2 (OAE2). In order to define the organic facies variability, this stratigraphic interval was analysed in the Baños de la Hedionda, a reference section positioned in the W part of the Internal Subbetic, representing the sedimentary record of a pelagic plateau located in the most distal part of the South Iberian Paleomargin. Regarding this goal, a high resolution study was developed on the Capas Blancas Formation (Capas Blancas, Black radiolaritic shales, and Boquerón members – Mb.), using organic petrographic and geochemical techniques. Carbon isotopic profile, for the isolated kerogen (δ13Ckerogen), displays a positive excursion of ~2.5‰ observed in the Black radiolaritic shales Mb., which is in accordance with the worldwide recognized trend for the OAE2 isotopic record.The pre-OAE2 is represented by the Capas Blancas Mb., with the majority of the samples of this unit showing no organic matter (OM) recovery (0.01—0.57 wt.% total organic carbon; TOC). Palynofacies analysis displayed an association co-dominated by the Amorphous and Palynomorph groups. The Amorphous Group is characterized mostly by marine phytoplankton-derived amorphous OM (AOM), while the Palynomorph Group is co-dominated by freshwater microplankton (Zygnemataceae and Closterium) and choanoflagellates, with some specimens of marine microplankton, sporomorphs, and zoomorphs being also identified. The mixture of freshwater and marine components suggest deposition in a platform environment with shallow depths and oscillating oxygen regimen (oxic to dysoxic conditions). The freshwater components are most likely transported into the marine system due to the lower amorphization state, with the source area being in high proximity.The OAE2, represented by the Black radiolaritic shales Mb., is characterized by a dominance of: (i) marine phytoplankton-derived AOM; (ii) plate-like bacterial AOM; and, (iii) sheet-like bacterial AOM with a cratered aspect (0.36—31.48 wt.% TOC). Choanoflagelates (with high degree of amorphization) at the base of the unit, zooclasts, sporomorphs, and solid bitumen are also present. The change in the organic facies suggests the occurrence of a transgressive phase. This organic facies is indicative of a relative sea level rise, with O2 conditions deteriorating with the emplacement of reducing conditions, possibly related to an increase in primary productivity.The post-OAE2, recognized in the Boquerón Mb., is characterized by a co-dominance of marine phytoplankton-derived AOM and palynomorphs, namely zoomorphs, and high percentages of opaque phytoclasts (below 0.25 wt.% TOC). Nevertheless, kerogen displays a reworked character and, therefore, data should be used with caution.Furthermore, this study constitutes the first record of Closterium in sediments from the Cretaceous, and the first identification of choanoflagellates, the closest living relatives of Metazoa, in the fossil record.

International audience; A new fauna has been collected from a fissure filling named Cos in the Quercy region, southwestern France. It includes four primate species and a plesiadapiform. The cercamoniine adapiform Protoadapis andrei Godinot and Vidalenc, nov. sp., is represented by material that adds to our knowledge of the genus Protoadapis for the upper canine, upper molars and other morphological details. It appears more primitive than P. brachyrhynchus from the Old Quercy Collections. The other cercamoniine Pronycticebus cosensis Godinot and Vidalenc, nov. sp., offers insight on intraspecific variations and other details of the genus. Both species suggest a bushy evolution within these genera. Two teeth document the presence of a third cercamoniine, Anchomomys sp. indet. The new microchoerid Quercyloris eloisae Godinot and Vidalenc, nov. gen., nov. sp., has very primitive characters and seems to document a primitive member of the Pseudoloris clade. A poorly documented paromomyid plesiadapiform is distinct enough to be named Arcius moniquae Godinot and Vidalenc, nov. sp. It represents the first discovery of a plesiadapiform in the Quercy fossil record and makes a link with paromomyids surviving until the late Lutetian European Mammal Paleogene MP 13 reference level. The primates indicate a broad age interval between MP 10 (late Ypresian) and MP 12 (mid-Lutetian). The identification of the same species of Pronycticebus and of the new genus in the Vielase fauna suggests more precisely the MP 10–MP 11 (late Ypresian–early Lutetian) time interval.

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 Cenomanian-Turonian boundary is marked by global sea-level highstands and one of the warmest periods of the Mesozoic, with high pCO2 levels linked to a massive magmatic episode. This is associated with the establishment of a worldwide marine anoxia, the deposition of organic-rich facies and disturbances of the global carbon cycle, the so-called Oceanic Anoxic Event 2 (OAE2). The Pont d'Issole section's (Subalpine Basin, SE France) sedimentary succession represents the reference record of OAE2 in the Tethyan domain, although its organic fraction is extremely poorly studied. Therefore, the main objectives of this study are the characterization of the Pont d'Issole section's organic matter (OM) for paleoenvironmental interpretation and the assessment of the OM thermal maturity using organic petrology and organic geochemistry techniques. The organic record characterizes a shallowing-up marine system with varying redox and restriction conditions, associated with periods of stratified oxygen regimen. It displays the presence of two OM enrichment episodes with different paleoenvironmental and geodynamic contexts. The first OM enrichment episode (Unit Th1) is thought to be associated with the global mechanisms that trigger OAE2 and is characterized by a palynofacies association co-dominated by amorphous OM and marine microplankton, reflecting a context of high sea-level. This is followed by the Plenus Cold Event (Unit Th2), characterized by a decrease in amorphous OM and increase in marine microplankton, representing a reoxygenation associated with an increase in water level, and an apparent decrease in temperature (disappearance of Classopollis sp.). The second OM enrichment episode (Unit Th3 and base of Unit Th4) is characterized by an association dominated by amorphous OM, the occurrence of freshwater microplankton, and the development of a restricted environment with low sea level. These depositional conditions are thought to be connected to the beginning phases of basin closure, promoted by the regional tectonic framework (compressive trend between Africa and Europe). The molecular fraction showed the presence of unsaturated compounds, monoaromatic steranes, monoaromatic anthrasteroids and the biological ββ hopanes, indicating a low thermal evolution for the OM. This is corroborated by biomarkers ratios and organic petrographic data, namely vitrinite reflectance (0.29% Rr). The presence of Paleozoic reworked OM in the samples was also identified presenting a more complex thermal history than the Cretaceous OM. This OM is possibly related to the subaerial erosion of Hercynian Massifs.

Upper Cenomanian–lower Turonian carbonates from the Preafrican Trough (South Morocco) and Agadir Basin contain biological (benthic and planktonic organisms) and chemical (redox-sensitive trace metals) markers indicating the occurrence of dysoxic conditions with a significant increase in productivity in shallow-water areas on the NW African margin during the Oceanic Anoxic Event 2. The geochemistry of carbonate rocks from three sections along a W-E transect, perpendicular to the margin, is studied here to elucidate the origin of the increased productivity and to test the applicability of cerium anomalies as markers of redox-sensitive and/or indicators of paleoenvironmental or paleoceanographic conditions. The rare earth element (REE) data show typical seawater patterns and negative Ce/Ce* anomalies which appear to indicate the persistence of oxic conditions during the late Cenomanian–early Turonian. This interpretation is in contradiction with that inferred from chemical data (ratios of various redox-sensitive elements to aluminum) and paleontological assemblages. To resolve this paradox, our data are compared with current oceanographic data and examined using a geochemical model that simulates the REE patterns of seawater, specifically the cerium anomaly. There is a satisfactory agreement between measured and calculated REE values for the three studied sections which allows us to distinguish Cenomanian and Turonian water masses. Taking all these geochemical data together, we suggest that the Cenomanian–Turonian stratigraphic interval in the Preafrican Trough and the Agadir Basin records a change of water mass during a transgressive event on an upwelling margin. The intense upwelling of nutrient-rich waters explains the high marine productivity throughout the studied area during the Turonian. The dissolved-oxygen concentrations in waters are not straightforwardly recorded in the trace-metal contents of carbonates. Nevertheless, these data can be deconvoluted by taking account of the saturation state of seawater and the role of particles. Even if negative cerium anomalies in carbonates are classically correlated with dissolved-oxygen concentration, this study proposes that they are also dependent, possibly to a large extent, on particle concentration and water-mass circulation. This would explain why several proxies are required to reconstruct paleo-redox conditions in carbonate facies.

The early Toarcian is marked worldwide by major environmental changes that resulted in organic-rich black shale deposition, the Toarcian Oceanic Anoxic Event (T-OAE). This organic-rich sedimentation is particularly recorded in the Grands Causses (GCB) and Quercy (QB) basins. The main objectives of this study are the characterization, through organic petrology and geochemistry techniques, of the organic matter (OM) of the late Pliensbachian – early Toarcian sedimentary successions of these basins and the definition of the organic facies, assessing their implications in the evolution of depositional paleoenvironments. In the GCB sedimentation occurred, during the late Pliensbachian, in a well oxygenated water body (Total Organic Carbon - TOC 0.6 wt.% and low Amorphous Organic Matter - AOM) proximal to the terrestrial source area (high terrestrial contribution) with marine influence. In the lattermost Pliensbachian a shallowing of the water column is observed with decrease of marine influence and separation from the terrestrial source area (TOC 0.9 wt.%, AOM and zooclasts co-dominate) under an arid climate ( Classopollis ssp.). From the Tenuicostatum to early Serpentinum chronozones a restricted and stagnated environment (TOC 5.7 wt.%, AOM dominates) is implemented. From middle to late Serpentinum Chronozone the reestablishment of the oxygen levels (decrease in TOC and AOM) takes place, as well as paleoceanographic circulation patterns. In the QB, the late Pliensbachian to earliest Toarcian is characterized by low TOC (0.2 wt.%) with sedimentation occurring in a shallow oxygenated proximal water body (amorphous Hydrozoans dominate) separated from the terrestrial source area with arid climate ( Classopollis ssp.), and with episodes of emersion. From the Semicelatum Subchronozone to Serpentinum Chronozone the development of dysoxic to anoxic conditions (TOC 4.2 wt.%) takes place, associated with water column stratification and more effective non-carbonate sedimentation, and with an increase in water level. For the lattermost Serpentinum Chronozone shallowing of a more oxidizing water body, with some oxygen depletion still present is proposed. The differences in these paleoenvironmental depositional contexts further demonstrate that, although the T-OAE has a global character, local control mechanisms in these basins play a pivotal role. Furthermore, the first occurrence of Hydrozoans, namely its free-swimming medusoid forms, is described in organopalynological preparations of sediments from the Pliensbachian–Toarcian and their first paleoenvironmental application in a palynofacies based study is made.

Thermal maturity of late Pliensbachian-early Toarcian organic-rich sediments in the Grands Causses (Sueges section), Quercy (Caylus section) and Pyrenean (Pont de Suert section) basins was determined through multiple parameters, including Spore Coloration Index (SCI), hydroid random reflectance (HRr) and spectral fluorescence of Tasmanites algae (λmax). The main objective of this study is to test the effectiveness and make comparisons of organic matter thermal maturity in these three sections by different techniques and particularly hydroid reflectance. For the Sueges section SCI presented a value of 3.5–4.0. HRr ranges between 0.36% and 0.47%, which corresponds to 0.45%–0.52% VReq, and shows a good correlation with SCI values. Spectral fluorescence analysis presents a λmax of 560 nm for most samples. The fluorescence spectral maximum seems to be redshifted in comparison to other thermal maturity parameters. The Caylus section exhibited SCI of 3.5–4.0. HRr ranges between 0.32% and 0.50% corresponding to 0.42%–0.54% VReq. Spectral fluorescence analysis points out a λmax of 560 nm, displaying a good correlation with SCI. When Req values determined through SCI are compared with equivalent vitrinite reflectance values determined through λmax, a redshift of the fluorescence spectrum maximum is detected. For the Pont de Suert section SCI ranges between 8.0-8.5 and 8.5–9.0. HRr varies between 0.85% and 1.18% which corresponds to 0.76%–0.98% VReq. Even though there are lower values than those obtained by SCI, VReq is reliable and acceptable to determine the thermal evolution stage. Furthermore, HRr values also present a good correlation with SCI. These data indicate that the majority of the samples from the Sueges and Caylus sections are in the immature to early mature evolution stages and Pont de Suert section samples are in late mature to early overmature evolution stages for liquid hydrocarbons generation, supporting a very similar thermal evolution for the Grands Causses and Quercy basins and an entirely different thermal history for the Pyrenean Basin. This is in accordance with the similar tectonic and sedimentary context of the Quercy and Grands Causses basins. The Pont de Suert section, located near the collision front of the Pyrenees mountains, records a more complex sedimentary and tectonic history. In addition, this study presents the first reflectance data for Jurassic hydroids, which show a good correlation with other rank parameters.

The study across the Pliensbachian–Toarcian boundary sedimentary record in the Bizanet section of the Pyrenean Basin (southern France) revealed the presence of solid bitumen. This secondary organic matter was characterized using petrographic (transmitted and reflected white lights, incident blue light, and scanning electron microscopy) and geochemical (total organic carbon, total sulfur, and insoluble residue) techniques. The spore coloration index (SCI) was also determined. With the characterization of the optical properties and reflectance of the solid bitumen, it was possible to distinguish four different families (A–D) that display a wide range of reflectance values, from 0.21% to 2.64% BRr, i.e., from glance pitch to meso-impsonite. SCI values were higher than 9–9.5 (%Req > 1.50%). The comparison between the equivalent vitrinite reflectance values of the solid bitumen and SCI showed that this index and the solid bitumen D values are concordant, indicating that solid bitumen D can be considered an indigenous bitumen. The other three families of solid bitumen (A–C) are considered as having migrated. The laterally equivalent Pont de Suert section (South Pyrenean Zone) displays no trace of solid bitumen which points to the important role of the morphotectonic context of the Bizanet section in the migration of these hydrocarbons, namely, the presence of a major thrust fault in the eastern Corbières close to the section’s location.

International audience; As the Messinian sea-level draw down associated with the Messinian Salinity Crisis is still questioned, we propose to show that the widely spread erosion surface affecting the Mediterranean margins is indeed linked to an exondation demonstrated from offshore and onshore data. Our study presents a comprehensive onshore to offshore correlation of the Messinian erosional surface. It is focused on small drainage systems or interfluve areas, outside of evaporite basins or incised canyons, where the Messinian erosion had not yet been studied previously: around Ibiza on the Balearic Promontory and around Orosei on the Eastern Sardinian margin, Tyrrhenian Basin, both areas where new offshore data were recently acquired. We show that the late Messinian erosion formed in subaerial settings, as testified by evidence of continentalization events, and attests for a regression phase that was correlated from the offshore continental slopes to the onshore paleo-platforms in both areas. Characteristics of this erosion in both study areas strengthen the scenario with at least one important low-stand sea-level for the Messinian Salinity Crisis with evaporites subbasins lying at different depths and possibly disconnected.; Depuis la découverte de la crise de salinité messinienne dans les années 70, le scénario proposant une chute importante du niveau marin associé à la mise en place des évaporites dans les plaines abyssales de la Méditerranée est régulièrement remis en cause. Nous montrons que la surface d'érosion affectant l'ensemble des marges est en effet liée à une émersion que l'on peut suivre à terre. Les observations présentées à terre s'attachent aux zones d'interfluves en dehors des bassins évaporitiques périphériques, là où la surface d'érosion messinienne n'a pas été étudiée : autour de l'île d'Ibiza dans les Baléares et autour d'Orosei sur la marge est-sarde. La surface d'érosion messinienne y est mise en évidence pour la première fois. Les données de sismique haute résolution récemment acquises dans ces deux zones nous permettent de présenter des corrélations terre-mer. Des évènements marquant clairement une continentalisation caractérisent la limite Mio-Pliocène dans les deux régions et atteste une phase régressive que l'on peut suivre des paléo-plateformes continentales à terre aux pentes du domaine offshore. Ces observations apportent des éléments pour étayer un scénario de la crise avec un bas niveau marin et des bassins évaporitiques à différentes paléo-bathymétries, possiblement déconnectés les uns des autres.

International audience; A rescue excavation at the site of Centre mobilisateur 10, located in the south-east of the Lannemezan agglomeration (Hautes-Pyrénées) and otherwise known as the Arsenal, was carried out in 2016 by the Éveha team, under the leadership of V. Ropiot. From a geographic perspective, this sector, between Bigorre and Comminges, occupies an interface position on a fluvio-glacially formed plateau, culminating at an altitude of 600 m at the foothill of the Pyrenees, and forms a vast expanse of land including heaths, bogs, meadows and some woodland. The excavation completely uncovered a circular tumulus with a pebble enclosure, which was the main aim of the operation. However, it also brought to light ten archaeological structures, including a singular megalithic monument, composed of a monolithic slab surrounded by a pebble border, covering a chamber buried in a vast oblong pit, with a frontal entrance. The other structures consist of six fireplaces with heated pebbles, two isolated post holes and a pit containing middle Bronze Age objects, which were plundered or heavily reworked but appear to be linked to worship rituals. All these structures are located in the central part of the excavated zone, around the tumulus, and towards the east for the hearths, including two developed in the crown of the tumulus. These remains are attributed to a period ranging from 3700 to 1400 BCE, centred around the Final Neolithic 2. They form an unprecedented monumental funerary complex in the High-Pyrenees.; Le site du Centre mobilisateur 10, situé au sud-est de l’agglomération de Lannemezan (Hautes-Pyrénées) et autrefois connu sous le nom de l’Arsenal, a fait l’objet en 2016 d’une fouille préventive réalisée par le bureau d’études Éveha, sous la responsabilité de V. Ropiot. D’un point de vue géographique, entre la Bigorre et le Comminges, ce secteur occupe une position d’interface sur un plateau de formation fluvio-glaciaire, qui culmine à 600 m d’altitude en piémont des Pyrénées, et qui constitue une vaste étendue comprenant des landes, des tourbières, des prairies et quelques bois. La fouille, en plus du dégagement complet d’un tumulus circulaire doté d’un enclos de galets, principal objet de cette intervention, a permis la mise au jour de dix structures archéologiques, dont un monument mégalithique de conception singulière, composé d’une dalle monolithe entourée d’une bordure de galets, recouvrant une chambre enfouie au sein d’une vaste fosse oblongue, comportant une entrée frontale comprise également dans l’excavation. Les autres structures sont six foyers à galets chauffés, deux trous de poteaux isolés et une fosse contenant du mobilier du Bronze moyen, pillée ou fortement remaniée mais vraisemblablement de nature cultuelle. Le tout se développe principalement dans la partie centrale de la zone prescrite, autour du tumulus, et vers l’est pour ce qui est des foyers, dont deux ont été aménagés dans sa couronne. Ces vestiges s’échelonnent sur une période comprise entre 3700 et 1400 av. n.è., l’occupation étant centrée sur le Néolithique final. Ils forment un ensemble funéraire monumental jusque-là inédit dans les Hautes-Pyrénées.

In Ibiza Island, we show for the first time that the post-tectonic late Miocene deposits are locally deformed in synsedimentary large scale boudinage structures. The late Miocene series is composed of a carbonate rich Unit 1 that is overlaid by a clastic Unit 2 and a Unit 3 in which a basal oolite-rich deposit is distinguished from an upper stromatolite-rich part. The oolite-rich and competent layers of Unit 3 are dissected into large rectangular to barrel-shape boudins that indicate a multidirectional extension. The separation of the blocks develops significantly northward revealing a stretching increase in a seaward direction that could have been favored by sliding of the distal part of the underlying marly unit over the clays. Along and in between the boudins, the laminated layers form soft-sediment syncline folds. The progressive bending of these laminated layers created spaces that were filled with calcite crystal wedges, providing evidence for large fluid circulation during deformation. Microthermometry on fluid inclusions in these calcite crystals revealed growth-temperatures ranging from 190 to 260 °C. This high recrystallization rate is an indication of important fluid circulation during deformation processes. Besides, the progressive infill of paleosols over some of the synsedimentary synclines indicates that deformation was a slow process during the emersion of the series. And the subaerial Messinian channels location in the topographic depressions formed by the boudinage of the late Miocene series confirms that the deformation and sliding occurred during the relative emersion associated with the Messinian Salinity Crisis. We thus interpret the boudinage as resulting from the destabilization of a still soft carbonate platform whose sliding has been helped substantially by the injection of relatively hot fluids. This work provides an onland evidence for extensional collapse during the Messinian sea-level drawdown.

The Mesozoic is marked by periods of profound climatic and paleoceanographic changes of the planet, representing major environmental perturbations and global carbon cycle disturbances, the so-called oceanic anoxic events (OAEs). These events are usually characterized by the deposition of sediments rich in organic matter (OM) which further validates the importance of the characterization of these organic records (e.g. Jenkyns, 2010). Furthermore, the high variability in the expression of these global events could be related to regional factors, which can be assessed through the study of the organic fraction of these records. With these premises is made a discussion about the organic variability, especially focused on petrographic observations, of two major OAE’s that differ in origin, extension and geochemical signature, the Toarcian (T-OAE) and the Cenomanian-Turonian (OAE2) events. For the T-OAE is analyzed a N-S transect of the Toarcian epicontinental seaway to enable the establishment of relationships of confinement, salinity and OM concentration. For the OAE2 the focus is on sections recording the Atlantic and Tethyan affinities to discuss the origin of the anoxia. The T-OAE organic record is characterized by the already established trend in TOC (van de Schootbrugge et al., 2005), with higher values being present in the more northern basins of the European epicontinental seaway (e.g. Dotternhausen) and diminishing towards the south, with lower values registered in the more external basins (e.g. Lusitanian Basin). This is coupled by a decrease in the degree of amorphization of the OM, and a variation in the origin of the amorphous OM, that culminates in its disappearance in the more external Lusitanian Basin (Fonseca et al., 2018; Rodrigues et al., 2016). The OAE2 organic record is marked by high variability, especially connected to differences in oceanic circulation dynamics that differ in the Tethyan and Atlantic domains (e.g. Trabucho-Alexandre et al., 2010). The TOC content of this event reaches higher values than the ones associated with the T-OAE (>30 wt.%), with the organic associations being dominated in the majority of the sections by amorphous OM. Nevertheless, the origin of this component differs and is very much controlled by local conditions. Differences in productivity, connected to the occurrence of intense upwelling in the Atlantic domain, are also observed. The organic facies variability and the differences in paleoenvironmental depositional contexts observed in the studied sections are associated with the regional character of both the T-OAE and the OAE2. These are mainly attributed to differences in paleogeography, paleogeomorphology and oceanic circulation patterns. Furthermore, there are clear differences in the organic content of both events, showing that is not only their origin, extension and geochemical characteristics that differ but also their organic signature.

The Early Toarcian is characterized by major worldwide environmental changes recorded in an organic-rich black shale sedimentation and carbon cycle disturbances, the so-called Toarcian Oceanic Anoxic Event (T-OAE) (e.g. Jenkyns, 2010). This organic-rich sedimentation is particularly recorded in shallow marine epicontinental basins that developed as part of the Toarcian European epicontinental shelf, paleogeographical framework in which the Pyrenean Basin is incorporated (e.g. Fonseca et al., 2018; McArthur et al., 2008). With these premises, the main objective of this study is to assess the organic facies variability and to define the depositional paleoenvironments of two sections from the Pyrenean Basin (Bizanet and Pont de Suert) during the T-OAE, using palynofacies and geochemical (Total Organic Carbon - TOC and insoluble residue - IR) data. The Pyrenean tectonics that occurred between the latest Cretaceous and the Oligocene, deformed, detached and fragmented the substrate resulting in diverse tectonic units (Faure, 2002). The late Pliensbachian-early Toarcian of the Pont de Suert section, located in the South Pyrenean zone, is characterized by the limestone dominated Barre a Pecten Formation (Fm.), and the carbonate and/or argillaceous-carbonate alternation of its three members (alternations of marl and argillaceous limestone of the Calcaires argileux à Spirifèrines Member (Mb.), the argillaceous limestones and marls of the Calcaires argileux et marnes à Soaresirhynchia Mb., and the marl and argillaceous limestone dominated Calcaires argileux à Telothyris Mb.; Faure, 2002). The Bizanet section is located in the eastern Corbières, and is characterized by a 3m thick succession of late Pliensbachian-early Toarcian sediments comprising, at the base, the limestone dominated Barre a Pecten Fm., followed by a sedimentary gap dated to the Tenuicostatum Chronozone, topped by the marly dominated succession of the Bizanet Fm. (black ferruginous marls intercalated with limestones and topped by dolomitic limestones of the Schistes carton Mb., and the black marls of the Argilites noires litées Mb.; Faure, 2002). The geochemical results evidenced that the Bizanet section presents higher TOC contents than the Pont de Suert section, with values reaching 2.03 wt.%. In the Bizanet section IR ranges between 12 wt.% and 82 wt.% and in the Pont de Suert section varies from 13wt.% to 67 wt.%, displaying a similar average value for the two sections (45 wt.%). The palynofacies assemblage is dominated in both sections by the same components, belonging to the Phylum Cnidaria, Class Hydrozoa and Order Hydroida, and are represented by fragments of colonial and non-colonial sessile polypoid forms and free-swimming medusoid forms, with different degrees of amorphization. (This abstract has been truncated, please see the complete PDF version)

The upper Cenomanian–lower Turonian paleoenvironments of the Preafrican Trough carbonate platform is characterized by analyzing the structure of the ostracod assemblages and the information provided by other groups, and also by linking together the paleontological and geochemical data (detrital influx-redox-paleoproductivity proxies, δ13C curve). Two different domains (eastern and western) can be recognized on the platform during the late Cenomanian, before the onset of the OAE2. The western domain corresponds to a low-energy environment developed on a mid and/or outer ramp with hypoxic waters, low detrital influx and low paleoproductivity. The paleoecological assemblages show limited specific diversity but variable density. The ostracods are opportunistic and unspecialized (r strategists), being associated with Buliminidae, surface and intermediate-water planktonic foraminifera, and fishes. The eastern domain corresponds to an inner ramp and/or peritidal environment with oxic waters, low detrital influx and low paleoproductivity, developed in a higher energy environment with paleoecological assemblages showing high diversity but variable density. The ostracods are more specialized (K strategists), being represented by diverse and constant assemblages associated with diversified benthic foraminifera, calcareous sponges and echinoderms, as well as intermediate- and deep-water planktonic foraminifera. The onset of the OAE2 has no influence on the western ostracod assemblages, but leads to the decline of the ostracod fauna and the disappearance of the deep-water planktonic foraminifera in the eastern domain. During the early Turonian, after the OAE2, the platform becomes an outer ramp with increased paleoproductivity, but is associated with a decrease of taxonomic diversity in hypoxic waters. The ostracods are very sparse and unspecialized, associated with siliceous sponges, Buliminidae, surface-living planktonic foraminifera, fishes and pelagic crinoids. Marine paleobiogeographic communication is relatively easy across the carbonate platforms between the Preafrican Trough and other Moroccan regions, as well as between Morocco and different parts of the South Tethyan and East Atlantic margins belonging to the Cenomanian–Turonian South Tethyan Ostracod Province (STOP). Thirteen new species are described: Cytherella tazzouguertensis n. sp., Bairdiacypris chaabetensis n. sp., Bythocypris amelkisensis n. sp., Pontocypris tadighoustensis n. sp., Procytherura? elongatissima n. sp., Loxoconcha akrabouensis n. sp., Hemiparacytheridea sagittaemucronata n. sp., Rehacythereis errachidiaensis n. sp., Rehacythereis zizensis n. sp., Veenia (Nigeria) tardaensis n. sp., Veenia (Nigeria) mediacostarobusta n. sp., Xestoleberis? preafricanensis n. sp., and Xestoleberis circinatus n. sp.

The main source rock (SR) of the Aquitaine Basin, the most important oil province in France, corresponds to organic-rich marine limestones of Upper Kimmeridgian age (Lons Formation in the Béarn area and Parnac Formation in the Quercy area). In order to better characterize their depositional environment, in particular the conditions of accumulation and preservation of organic-matter, a sedimentological, micropaleontological and geochemical study of the Crayssac section (Quercy) has been performed. Organic-rich sediments are argillaceous limestones (65 to 99% CaCO3) organized in repetitive beds of up to 1-m thickness. Their total organic matter content reaches up to 15 wt.%, and in this SR kerogen is type of II and immature. Microfauna content, the lack of barrier facies and the control of the wave action base over the depositional environments reflect deposition in an open marine type homoclinal ramp. Strong similarities with Kimmeridgian organic-rich limestones of the Middle East (Hanifa Formation) suggest that the Parnac Formation could act as an analogue of this prolific SR.

The Upper Cenomanian–Lower Turonian deposits of the Preafrican Trough, Morocco, are composed by fossil-rich limestones accumulated in environments ranging from the peritidal zone to the outer ramp. Two distinct domains appear during the Late Cenomanian; to the east and south-east, shallow-water sedimentation predominates in the peritidal zone and the inner ramp, while, to the west and north-west, sedimentation develops on the mid-ramp and outer-ramp. The late Cenomanian Oceanic Anoxic Event 2, OAE2, is well recorded by δ13C excursions in all the depositional environments, even in shallow water. Despite the lack of black shale deposits, the presence of buliminids indicates occasionally dysoxic conditions in the western domain during the OAE2. The maximum flooding and deepening phase (drowning) is dated as Early Turonian (post-OAE2), associated with outer ramp sedimentation over the whole area. Dysoxic conditions, indicated by laminated and silicified limestones rich in buliminids, prevail at the scale of the Preafrican Trough. Shallower marine environments and oxic conditions appear once again at the end of the Early Turonian.

An integrated analysis of the Hauterivian shallow-marine carbonates from the western margin of the Lusitanian Basin (Portugal) allows us to assess the paleoenvironmental significance of variations of biological, mineralogical, chemical and magnetic markers in a lagoonal environment. The Guincho section is characterized by nine facies included in different environments ranging from terrestrial and restricted lagoon to high-energy open platform. The variations of the different markers show a clear cyclic pattern. Certain curves are relatively well correlated, thus exhibiting a parallel trend, while others are anti-correlated. In this shallow water context, there is relation between the habitat [biocoenosis] and concentration of benthic foraminifera, the presence and activity of boring and micritizing organisms, the detrital input expressed by magnetic susceptibility (MS) as well as the chemical and isotopic composition of the carbonate fraction (especially K content and δ 13 C). In this lagoonal environment, the increasing detrital input appears to reduce the relative density of infaunal benthic foraminifera in favor of epifaunal benthic foraminifera. These conditions lead to the development and prevalence of large benthic foraminifera with agglutinated tests, more particularly Choffatella decipiens . At the same time, there is a reduced activity of organisms, such as endolithic algae and cyanobacteria, which cause micritization of the grains; as a result, the δ 13 C decreases while the magnetic susceptibility (MS) and K content increase. This detrital input increases the water turbidity, which modifies the faunal composition, which in turn has an effect on photosynthesis activity. In the studied area, the positive δ 13 C excursion is associated with enhanced carbonate accumulation and production, while a negative shift in δ 13 C is recorded during episodes of increased clay input. This relationship can be explained by carbonate precipitation by whitings. During episodes of high detrital input, photosynthesis activity decreases, which leads to a decrease in carbonate precipitation and δ 13 C values. This detrital input appears to be controlled by variations of rainfall on the continent.

Joint density is studied in relation to petrographic and petrophysical parameters in two sedimentary carbonate formations characterized by different diagenetic histories: the Kimmeridgian limestones of the Chay Peninsula (western France) with a mean joint density of 6.37 fractures per meter (fr/m) (1.94 fr/ft), and the Bathonian limestones of the Bouye outcrop (western France) with a mean joint density of 1.9 fr/m (0.58 fr/ft). The Chay carbonates are characterized by a lower CaCO3 content, a higher average porosity, and a lower sound velocity than values recorded in the Bouye limestones. The compressive strength and Young's modulus of the Bouye carbonates are, respectively, 10 and 3 times higher than in the Chay carbonates. A statistical analysis was used to identify relationships between joint density and carbonate rock properties. When facies variations are marked, the joint density at outcrop scale is related to the mean bed thickness, the facies descriptors, and the Young's modulus. When textural variations are more limited, the joint density is controlled by the porosity. At the scale of a sedimentary basin, 63.8% of the variation in joint density may be accounted for by Young's modulus and the sparite/micrite ratio. The decrease in the sparite/micrite ratio reflects an increased number of grain boundaries in the carbonate rock, which limits grain deformation and enhances joint density. The variations in Young's modulus depend essentially on the porosity and mineralogy of the studied rocks. Any increase in CaCO3 content or decrease in porosity is associated with an increase in the elastic properties of the rock and a reduction of joint density.

International audience; A synthetic study was carried out based on sedimentological, palaeontological, geochemical and mineralogical data of the upper Cenomanian lower Turonian carbonate platform of the Preafrican Trough (eastern Morocco) in order to (1) propose a 3D representation of the platform and constrain the temporal framework of the dysoxic/anoxic episodes recorded during the OAE2, (2) define and discuss the prevailing climate on the platform during this period, and (3) make comparisons with other Cenomanian Turonian platforms. During the late Cenomanian, both before and during the CCIE (Cenomanian Carbon Isotope Excursion), the platform displayed an east west polarity. Three third-order sequences of transgression regression can be defined. Dysoxic conditions were developed in the sediments and the bottom waters of the deepest environment (mid- to outer-ramp setting), in the western part of the platform. Well-oxygenated waters were present in the eastern part of the platform (peritidal zone to mid-ramp environment). The climate was arid before the CCIE, becoming warm with contrasted seasons during the CCIE. This climate is associated with a low palaeoproductivity over the entire platform, along with the presence of photozoan followed by heterozoan carbonate-producers, as found also in other parts of the Saharan platform. However, such conditions are not in accordance with many studies which suggest a wet climate during the CCIE, leading to intense chemical weathering of the continent favouring the appearance of high palaeoproductivity at a global scale and the establishment of dysoxic/anoxic conditions. In the Preafrican Trough, poorly-oxygenated waters spread outwards from the deep basins and covered the platform in response to sea-level rise. Many disturbances are recorded in the platform succession during the early Turonian, after the CCIE. Indeed, just after the C/T boundary, the development of an outer-ramp environment over the entire Preafrican Trough reflects flooding of the platform, linked to the end of the major Cenomanian transgression and the presence of eutrophic conditions which disrupted carbonate-producing organisms. This high palaeoproductivity, due to considerable nutrient input, led to the establishment of highly dysoxic/conditions in the bottom and intermediate waters, causing the disappearance of the majority of the Cenomanian palaeontological groups, except for the opportunist benthic and planktonic foraminifera which proliferated. Part of the nutrient input could be due to the presence of a hot and wet climate that may have led a slight increase in the degree of chemical weathering of the continent. Nevertheless, many lines of evidence, such as the decrease of the detrital influx during the early Turonian and the reduction of the weatherable continental areas after the Cenomanian transgression, suggest the existence of another source of nutrient inputs. Combined with the presence of dysoxic/anoxic conditions during the lower Turonian in several regions of the tropical Central Atlantic, the occurrence of these nutrient inputs may be linked to the volcanism/hydrothermalism of the Caribbean LIP and the mid-ocean ridges.

The successive levels of a section are compared independently with a reference level (referential) having well identified characters. The comparison is realized by means of a distance or dissimilarity index. The choice of the index as function of the nature of data is argued, as well as the choice of the referential. This new approach is applied to the study of two examples from liassic series of southern France. The treatment of micropaleontological or faciological datas reveals cycles that are coincident with 3rd order eustatic cycles.

In the Quercy basin, the passage from the Liasic marls to the Dogger carbonates depends on three interdependent allocyclic factors. The long wavelength allocyclic factor (eustatism) shows a certain uniformity of the variations of the accommodation to the basin scale. The regional allocyclic factor (uplift) gives way to a partial isolation of the platform. The weak wavelength allocyclic factor (local tectonics) leads to a parcelling with various blocks of different scale.

Using the example of the upper Hauterivian in the Lusitanian Basin, we demonstrate a climatic control of cyclic variations in the biological, mineralogical, chemical, and magnetic markers in a lagoonal environment. In a lagoonal setting, variations in detrital supply, controlled by climate changes, modify the water turbidity. During humid climatic conditions, the increase in water turbidity reduces light penetration and photosynthetic activity. The reduced precipitation of carbonates is probably due to the low concentration of cyanobacteria or unicellular green algae, and is associated with a decrease in micritization processes. Another consequence of the increase in detrital supply is the reduction in benthic foraminifera, with the development of infaunal forms in favour of epifaunal forms, and the proliferation of large agglutinated foraminifera such as Choffatella decipiens. During dry climatic conditions, this tendency is reversed and there is an enhanced contribution of Miliolidae. Thus, in this lagoonal setting, climatic variability (controlled by orbital parameters) modified carbonate production, the faunal assemblages, and the water chemistry.

15 pages; International audience; The Early Toarcian oceanic anoxic event (OAE) is associated with a rapid and severe environmental change whose causes are still a matter of debate. A new paleoenvironmental interpretation is proposed, based on a multidisciplinary dataset (chemical, mineralogical and paleontological) obtained from a borehole drilled by Andra (French National Radioactive Waste Management Agency) in the Lower Toarcian of the eastern Paris Basin (France). During the earlymost Toarcian (TenuicostatumZone), the presence ofwell oxygenated sea-water is reflected by an abundant and diverse fauna, alongwith paleoredox proxies (U/Al, Mo/Al and V/Al) typical of oxidizing conditions, associated with predominant mechanical weathering on the continent. At the base of the Serpentinum Zone, an important paleoenvironmental change is marked by an initial phase of organic matter enrichment (~12% TOC) during the negative shift of δ13C (Carbon Isotope Excursion: CIE). Euxinic/anoxic conditions, indicated by cobalt enrichment and the development of framboidal pyrite, lead to the disappearance of the benthic and pelagic fauna and alloworganic matter to be preserved in the sediments. At this time, the lowconcentration of paleoproductivity proxies (Cd, P, Ni and Zn) suggests weak chemical weathering on the continent due to a rather arid climate. Low concentrations of Sr and coccoliths are due to an input of fresh water probably coming from the Arctic through the Laurasian seaway. Thus, the isolation of the Paris Basin from the Tethyan realm and the influx of freshwater favour haline stratification and the preservation of organic matter. Following the CIE, oxygen concentration gradually increases up to amaximumflooding surface dated as coevalwith the Serpentinum Zone, Elegantulum Subzone. Paleoproductivity proxies indicate a weak primary productivity. The top of the Lower Toarcian is characterized by a second enrichment in organic matter (~12% TOC) due to an important input of nutrients. This enhanced primary production generates euxinic/anoxic conditions in the sediment and in part of the water column, leading to a high enrichment in paleoredox proxies (Mo, U, V, Co) and causing the sudden disappearance of the benthic fauna and a progressive decline of the pelagic fauna. The metal enrichment is related to intense chemical weathering on the continent due to a more humid climate.

Geochemical analyses (major and trace elements) and palaeontological studies were carried out based on rock samples and thin sections collected from three outcrop sections (Goulmima, Ziz and Tazzouguert) in the upper Cenomanian–lower Turonian in the carbonate platform of the Preafrican Trough (South Morocco), in order to determine if oxygen-depleted conditions affected the platform, and to highlight the possible impact of oxygen variation on carbonate production, particularly during the Oceanic Anoxic Event 2 (OAE2), which took place in the late Cenomanian. During this interval, the carbonate platform was composed of two contrasting environments. A shallow-water environment (peritidal to mid-ramp) was developed in the East (Ziz and Tazzouguert sections), characterized by a high diversity and abundance of benthic organisms, and in some cases, by a high diversity of planktonic organisms, associated with low concentrations of authigenic markers (U, Mo, V and Cr: redox proxies), indicating oxic conditions. In the West (Goulmima section), the environment was deeper (mid ramp/outer ramp) and redox proxies record a high enrichment, an indicator of reducing conditions, associated with a low diversity and abundance of organisms and the presence of Buliminidae. Bottom waters were dysoxic and the palaeoproductivity was low at the sea surface. Thus, during the late Cenomanian, oxygenation conditions were relatively good over the area of the Preafrican Trough, even during the OAE2, except in the deeper environments toward the West, where bottom waters were depleted in oxygen. During the Cenomanian transgression, and more precisely during the OAE2, this dysoxia was linked to the influx of poorly-oxygenated waters from the deeper anoxic basins of the Atlantic and/or Tethys oceans. Geochemical, palaeontological and sedimentological disturbances are recorded in the lower Turonian everywhere in the outer-ramp environments of the platform. Palaeontological proxies show a huge decrease in group diversity, with the disappearance of benthic foraminifera – except for the Buliminidae which proliferated – and only shallow-water planktonic foraminifera survived. Geochemical proxies of redox conditions and palaeoproductivity show a marked enrichment in all three outcrop sections, with higher values in the West. This dysoxia occurred in response to a climatic change, from warm with contrasting seasons to hot and wet, which induced an increase of chemical weathering in the Anti-Atlas to the southwest of the platform. This substantial input of nutrients increased the palaeoproductivity, which finally enhanced the consumption of O2 owing to the decay of organic matter. Moreover, the late Cenomanian transgression led to the supply of additional nutrients to the platform, due to the leaching of soils.

International audience; Joint aperture and joint development have been studied in the Kimmeridgian limestones of the Pointe-du-Chay, at the northern boundary of the Jurassic Biscay Basin (France). At Belette outcrop, in some layers the mean joint spacing of the N120° joint set is close to mean layer thickness. There, the classical spacing to thickness relationship appears to be valid in the competent carbonate layers that are included in a more argillaceous matrix. At Pillar outcrop, the N10° joint set is characterised by a high level of joint density and a non-saturated spacing distribution as indicated by the mode/mean ratio values and the Cv values; Cv is the ratio of standard deviation to mean fracture spacing. The classical relationship between layer thickness and fracture spacing has not been observed at the Pillar outcrop. Joint aperture reaches larger values at the Pillar outcrop than at the Belette outcrop where aperture is more homogeneously distributed. Almost all the joints are opened with moderate aperture values at Belette outcrop whereas most joints with large vertical dimension have large apertures at Pillar outcrop, and smaller fractures are closed or poorly opened. From two outcrops that have been subjected to the same geological conditions, apertures of non-stratabound joints appear to be controlled by the vertical dimension of the joints whereas stratabound joints are more regularly spaced and opened.

On the eastern edge of the Aquitaine Basin, the Lias-Dogger transition and the events, which occurred during this time interval are studied in the Quercy sedimentary basin. Stratigraphic correlations are proposed using a biochronological calibration based on the determination of numerous ammonites and brachiopods. Facies analyses using statistical processing integrate the presence of faults and tectonic compartments and lead to reconstruction of palaeoenvironments in space and time. The paper includes the description of system tracts following Haq et al. [1987] and Vail et al. [1991], and twelve palaeogeographic maps of the area studied. The objectives are to distinguish the various allocyclic and autocyclic factors controlling sedimentation and to show the impact of the Mid-Cimmerian tectonic event on the evolution of the basin.

Durlet Christophe, Alméras Yves, Chellaï El Hassane, Elmi Serge, Le Callonnec Laurence, Lézin Carine, Neige Pascal. Anatomy of a Jurassic carbonate ramp : a continuous outcrop transect across the southern margin of the High Atlas (Morocco). In: Géologie Méditerranéenne. Tome 28, numéro 1-2, 2001. Anatomy of Carbonate Bodies / Anatomie des corps carbonates. International Meeting / Colloque international. Marseille, 9-12 mai 2001, France, sous la direction de Marc Floquet, Jérôme Hennuy et Jean-Pierre Masse. pp. 57-61.