La formation de Martin Bridge du Trias Supérieur (Carnien-Norien, Wallowa Terrane, Oregon): implications sédimentologiques, biostratigraphiques et paléo-bio-géographiques

Upper Triassic studies of carbonate platforms are strongly unbalanced. In the Tethys, wide investigations for over 100 years provide reliable sedimentologic, paleontologic, paleogeographic, and stratigraphic frameworks. However, in Panthalassan tropical to subtropical carbonate deposits, only a handful of works exist. Thus, the correlations and paleobiogeography far from the Tethys remain a mystery yet to be solved.

Considering Panthalassan remnants, the Upper Triassic deposits of the Wallowa terrane (Oregon, USA) show one of the highest affinity with the Tethyan localities. Therefore, the terrane appears as a predisposed candidate to constrain potential correspondences between Tethys and Panthalassa. Our project aims to reconstruct the Martin Bridge Fm carbonate platform, notably using foraminifers, in order to compare the deposits with those of coeval Tethyan localities. The succession, closely associated with the cessation of volcanism of the Wallowa volcanic island-arc, overlies the Permian to Triassic Seven Devils volcanic and volcaniclastics and is overlain by the Triassic-Jurassic Hurwal argillites.

The detailed logging section and sampling for sedimentological, paleontological and geochemical analyses mainly come from shallow-shelf and reefal carbonates.

Research takes place in the field of biostratigraphy, systematic paleontology, sedimentology, geochemistry and palaeobiogeographic reconstructions.