Palaeobathymetric reconstruction of peritidal carbonates: Late Barremian, Urgonian, sequences of Provence (SE France)

Peritidal platform carbonates of Late Barremian age (Early Cretaceous) cropping out in the Marseille region (Provence, SE France) tend to be arranged stratigraphically in deepening-up or shallowing-up sequences. Seven facies types (lithofacies) were defined in the studied stratigraphic interval, ranging from supratidal to shallow subtidal settings. There is a good correspondence between the inferred relative water depth of facies and their average bed thickness. Cumulative thickness of facies types expresses quantitatively their palaeobathymetric range and provides an estimate of their average water depth. Calculations show that the palaeobathymetry of supratidal/intertidal facies types is from 0 to 40 cm, i.e. a pertaining to a palaeotidal (microtidal) range. The average palaeobathymetry of rudist facies, ascribed to subtidal settings, fluctuates between 40 cm and nearly 160 cm. Measuring a large number of beds belonging to both shallowing-up and deepening-up sequences, and averaging the results, appear relevant to minimise the effect of compaction, pressure solution and synsedimentary progressive or abrupt changes in accommodation, which are expected to modify bed thickness and its original palaeobathymetric significance. The method proposed here has a good potential for palaeobathymetric reconstruction of ancient peritidal carbonates.