Yves Gourinard

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.

Sequence Stratigraphy and Grade-Dating in the Senonian Series from the South-Pyrenees (Spain), the Sedimentary Record of Eustacy and Tectonics

A new stratigraphic procedure that combines sequence stratigraphy and grade dating based on chronometric calibration of Rosita fornicata lineage evolution is applies to the analysis of the South Pyrenean Senonian Basin. These methods give eustatic and biometric curves both constructed according to Haq’s chronology and they permit time-correlations without variations in accuracy. In this way, two kinds of stratigraphic units are recognized and numerically dated from the Senonian-Early Danien in the South-Pyrenean foredeep Basin. These units are: eustatically-controlled depositional sequences; and tectonically-controlled depositional sequence sets.

Continu et discontinu dans une évolution de foraminifères planctoniques du Crétacé supérieur

Abstract Within the populations of the gradual lineage including Contusotruncana fornicata ( Plummer ) ( Globotruncanidae ), the spiral heights increase with time. The speed of this increase is linked to the asymmetries in the distributions of the index used to measure the spiral heights. The succession of these asymmetries shows an evolutionary process, combining gradualist continuity and discontinuities by successive evolutional jumps. These two coexisting modes could be induced by genetic mechanisms evoked for phyletic gradualism and punctualism respectively.

Sr-ages and grade-datings in the area of the Lower Miocene near Bordeaux (Aquitaine Basin, France)

Abstract Twelve Sr-ages, recently obtained within the Aquitanian and Burdigalian deposits near Bordeaux are consistent with the grade-dating already published from the same localities. These two interpolation methods of radiometric ages support each other.