Magnetostratigraphy of the Maastrichtian continental record in the Upper Aude Valley (northern Pyrenees, France): Placing age constraints on the succession of dinosaur-bearing sites

Abstract

The first detailed stratigraphic succession of the Upper Cretaceous continental record from the Upper Aude Valley (southern France) is presented together with a magnetostratigraphic study. The combined stratigraphy and magnetostratigraphy of the Marnes rouges inférieures Fm (Lower Red Marls), constrained by biochronological markers such as charophyte occurrence and revised dinosaur eggshells, results in a succession of fluvial red beds dated from chron C32n to the top of chron C31r. It implies an earliest Maastrichtian age close to the C32n.1n-C31r reversal for the majority of the dinosaur sites including Bellevue. In contrast, the upper Maastrichtian is likely represented by a short interval within the lacustrine-palustrine Calcaires et argiles de Vignevieille Fm (Vignevieille Limestones), or it might even not be recorded. The proposed age indicates that the marine to continental transition, as a result of the Late Cretaceous transgression, took place earlier in the north Pyrenean basin than in the southern area.