ASTRONOMICAL CONTROL OF CARBONATE RECORD IN THE LOWER CRETACEOUS OF THE VOCONTIAN BASIN (SE FRANCE)
Résumé
A study of variations in carbonate productivity, quantified by calcium carbonate content for a Valanginian-Hanterivian interval, is presented from the Angles-Vergons series (Vocontian basin). Spectral analysis techniques reveal the presence of significant carbonate cycles linked to cyclic variations of the Earth's orbit, The results suggest that the obliquity cycle is the most clearly defined signal whereas the presence of carbonate cycles related to the precession signal is less distinct. The transition from limestone-dominated alternations to marl-dominated alternations is characterized both by an increase of sedimentation rate and a change from the precession cycle being the dominant forcing factor in the calcareous part to the predominance of the obliquity cycle in the marly part. An orbitally calibrated chronology is presented for the Valanginian-Hanterivian interval based on the identification of carbonate cycles.