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Candidate sections for the GSSP of the base of the Bathonian Stage (Middle Jurassic)

Fernandez-Lopez S.

Volumina Jurassica

2009

Vol. 7, no. 1

77-88

In accordance with the recommendations of the International Commission on Stratigraphy (ICS), the leading candidate for the Global Boundary Stratotype Section and Point (GSSP) of the base of the Bathonian Stage is located in the Ravin du B?s (Bas Auran area, SE France). This section was formally proposed as candidate nineteen years ago. A second potential candidate section is located in the Cabo Mondego area (Portugal). This Portuguese section, however, has not been formally proposed as a candidate for the Bathonian basal boundary stratotype. The formal selection and proposal of a GSSP for the Bathonian Stage is the responsibility of the Bathonian Working Group (BtWG) and is expected by September 2007. In accordance with the procedures to ratify GSSPs, a formal ballot on the selection and proposal of a GSSP for the Bathonian Stage, by post or email, by all members of the BtWG is the responsibility of the convenor and the International Subcommission on Jurassic Stratigraphy Executive, and will be carried out within this time scale.

Global Jurassic tetrapod biochronology

Lucas S.

Volumina Jurassica

2008

Vol. 6, no. 1

99-108

Jurassic tetrapod fossils are known from all of the continents, and their distribution documents a critical paleobiogeographic juncture in tetrapod evolution – the change from cosmopolitan Pangean tetrapod faunas to the provincialized faunas that characterize the late Mesozoic and Cenozoic. Two global tetrapod biochronological units (faunachrons) have been named for the Early Jurassic – Wassonian and Dawan – and reflect some Early Jurassic tetrapod cosmopolitanism. However, after the Dawan, a scattered and poorly-dated Middle Jurassic tetrapod record and a much better understood Upper Jurassic tetrapod record indicate that significant provincialization of the global tetrapod fauna had begun. Middle Jurassic tetrapod assemblages include distinct local genera of sauropod dinosaurs, which are large, mobile terrestrial tetrapods, and this suggests marked provinciality by Bajocian time. The obvious provincialism of well known Chinese Middle-Upper Jurassic dinosaur faunas also documents the end of tetrapod cosmopolitanism. The distribution of some Late Jurassic dinosaur taxa defines a province that extended from the western USA through Europe into eastern Africa. Provincial tetrapod biochronologies have already been proposed for this province and for the separate eastern Asian Late Jurassic province. Tetrapod footprints only identify two global assemblage zones, one of Early Jurassic and the other of Middle-Late Jurassic age. The incomplete state of Jurassic tetrapod biochronology reflects both an inadequate record with poor temporal constraints and a relative lack of study of the biostratigraphy of Jurassic fossil vertebrates.