Paule Eichène

Stratigraphie séquentielle comparée et ≪ gradedatation ≫ par les foraminifères planctoniques du Campano-Maastrichtien et du Paléocène de quelques sites d'Europe sud-occidentale et d'Afrique du Nord

From the analysis of the open marine beds enclosing the K/T boundary along several cross-sections of SW Europe and North Africa, a subdivision is proposed into nine Campanian-Maastrichtian depositional sequences followed by five Palaeocene sequences. These sequences have been correlated from one section to another by means of planktonic Foraminifera classic biozones and supported in the Cretaceous by numeric ages coming from the grade-dating method applied to Globotruncanids. In the latter case, sequences belong to two different types separated by the presence or the absence of lowstand chaotic deposits such as breccias and olistostromes. The dark clays of the K/T boundary containing the Iridium anomaly can be regarded as a 3d order sequence boundary. They also correspond to the base of a 2d order cycle which is locally (Beam) underlined by a gap of the Early Palaeocene, the underlying Maastrichtian marls, everywhere grade-dated around 65.2–65.3 Ma, never being significantly eroded.

Mise en évidence d'un sillon marin à brèches paléocènes dans les Pyrénées centrales (Zone interne métamorphique et Zone nord-pyrénéenne)

Abstract The discovery, in several localities, of significant planktonic Foraminifera, Danian–Selandian in age (P1c–P3 interval), both in the matrix of polygenic, post-metamorphic and post-tectonic debris-flow breccias (Comus Breccia Fm.) and in argillaceous hemipelagites, interbedded within these breccias, evidences the occurrence, during Palaeocene, of a longitudinal east–west marine trough, particularly open towards the Atlantic Ocean, within the present Internal Metamorphic Zone (and adjacent North-Pyrenean areas) of Central Pyrenees, from Aude to Haute-Garonne. This new dating shows the major importance of the Upper(most) Cretaceous compressions in the structuration of the tectorogenic axis of the range.

L’ olistostrome coniacien de Lordat (Pyrénées ariégeoises) et son équivalent latéral de Vicdessos, témoins d’un nouveau bassin d’avant-pays au front nord de la Haute Chaîne Primaire

ResumeDe nouvelles datations et grade-datations fondees sur les Foraminiferes planctoniques, ponctuellement identifies en depit d’un epimetamorphisme campanien, permettent de doubler voire a triper l’etendue du « sous-bassin » coniacien de Lordat (Zone des Ecailles Bordieres, Ariege), en partie calciturbiditique, aux depens terrains jusqu’a present tenus pour paleozoiques, tels ceux de l’ex-« Ecaille paleozoique de Lordat ». Ces derniers correspondent a des olistolithes de tres grande taille au sein d’un vaste olistostrome (château de Lordat, ermitage de Saint-Pierre), lui-meme inclus dans une epaisse serie monoclinale, a dominante calcschisteuse, constituant un probable equivalent lateral du « Flysch a Fucoides ». Cette serie deborde vers le Nord jusque sur la Zone Interne Metamorphique, comme le demontre l’âge neocretace du lambeau ex-paleozoique de Carmilles, directement chevauche par le massif Primaire nord-pyreneen de Saint-Barthelemy. Plus a l’Ouest, le « sous-bassin » de Vicdessos, prolongeant celu...

La limite Crétacé-Tertiaire en domaine marin dans les Pyrénées centrales (zone sous-pyrénéenne, France)

Abstract The discovery of Paleocene planktonic Foraminifera (subzones P1c to P3b) in the western sub-Pyrenean zone (Haute-Garonne) made it possible to locate an anomalously high abundance of iridium at the Cretaceous-Tertiary boundary underlining the interface between the ‘calcaires a Bryozoaires/calcaires a Algues, of Larcan-Nizan’, newly assigned to Danian-Selandian and the underlying ‘marnes bleues de Saint-Loup’, the top of them being Uppermost Maastrichtian in age (Hariaensis zone and grade-datation of 65.47 Ma). A short gap (subzones P0 to P1b, Lowermost Danian) probably marks, as in Bearn, the base of the Paleocene Larcan-Nizan Bryalgal limestones.