Geochemical characterization (Mn content) of third order eustatic sequences in Upper Jurassic pelagic carbonates of the Vocontian Trough (SE France).

The manganese contents of the Oxfordian-Kimmeridgian pelagic carbonates the section at Chateauneuf d'Oze (Vocontian Basin, Hautes Alpes, France) are u sed to define 11 geochemical units. These units are interpreted in terms of sequence stratigraphy and grouped into 6 third-order sequences, which then are compared with those of the sequence-chronostratigraphic chart of Hard- enbol et al. (1998). Using this approach, two modifications to the chart ar e proposed: (i) the Oxfordian-Kimmeridgian boundary in the Tethyan realm should be set in the upper part of the Hauffianum subzone, as clearly proposed by biostra tigraphic studies from Wierzbowski (1991), Atrops et al. (1993), and Schwei gert & Callomon (1997), (ii) a new sequence (Kim2') should be introduced in the Hypselocyclum zone, and the sequence Kim2" (Hypselocyclum - Divisum zones) becomes the equival ent of the cycle chart Kim2 sequence.