An Extended Field of Crater Structures in Egypt: Observations and Hypotheses

We detected more than 1000 crater structures in the Western Egyptian Desert, distributed over 40000 km2, among which 62 were studied on the field. Two hypotheses are proposed for their origin: hydrothermal vent complexes or impact craters generated by a rubble-pile asteroid

Mesozoic biostratigraphic, paleoenvironmental, and paleobiogeographic synthesis, equatorial Atlantic

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

Analyse palynologique de l'argile lignitifère à ambre de l'Albian terminal d'Archingeay (Charente Maritime, France).

Un niveau d’argile lignitifère à ambre, provenant de l’Albien terminal affleurant dans une carrière située sur la commune d’Archingeay (Charente-Maritime, France), a livré une association palynologique bien conservée, riche et diversifiée, d’origine mixte, continentale et marine. Son étude détaillée, en microscopie optique et électronique, permet d’en dresser l’inventaire, puis de proposer une reconstitution du paléoenvironnement et de déduire le paléoclimat qui régnait sur cette région : un milieu estuarien sous un climat plutôt humide, tempéré à chaud. Le paysage du rivage et de l’arrière-pays devait être essentiellement composé de fougères variées, d’autres ptéridophytes et de conifères producteurs de la résine ayant évolué en ambre ; l’affinité angiospermienne est remarquable, bien qu’encore modeste sur le plan de la diversification. Des « algues » filamenteuses peuplaient les cours d’eau. La microflore d’origine marine, de diversité modérée, comprend des « basales » chitineuses de foraminifères, des acritarches et des kystes de dinoflagellés, parmi lesquels figurent les taxons repères de l’Albien terminal ; la dominance des espèces néritiques reste cependant mesurée