ASTRONOMICAL CONTROL OF CARBONATE RECORD IN THE LOWER CRETACEOUS OF THE VOCONTIAN BASIN (SE FRANCE)

A study of variations in carbonate productivity, quantified by calcium carbonate content for a Valanginian-Hanterivian interval, is presente d 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 th e obliquity cycle is the most clearly defined signal whereas the prese nce of carbonate cycles related to the precession signal is less disti nct. The transition from limestone-dominated alternations to marl-domi nated alternations is characterized both by an increase of sedimentati on rate and a change from the precession cycle being the dominant forc ing factor in the calcareous part to the predominance of the obliquity cycle in the marly part. An orbitally calibrated chronology is presen ted for the Valanginian-Hanterivian interval based on the identificati on of carbonate cycles.