Stable carbon isotope stratigraphy of the Paleogene pedogenic series of southern France as a basis for continental-marine correlation

Abstract

The Upper Cretaceous–lower Paleogene formations in the Aix-en-Provence basin are characterized by interfingering lacustrine carbonates and flood-plain alluvium. The deposits from both environments display numerous horizons of carbonate-rich paleosols. By using a combined magnetostratigraphy and carbon isotope stratigraphy for the pedogenic carbonate glaebules, we constructed a detailed integrated stratigraphy for the entire lower Paleogene. This method provides a way to correlate marine and terrestrial sequences when C3 plants dominated the environment. Both long-term and short-term δ¹³C variations were identified in the Provence series: (1) the uniform carbon isotope record established through the end of the Maastrichtian followed by the abruptly negative carbon isotope excursion in the lowermost Paleocene provides a marker for the precise location of the Cretaceous-Tertiary boundary in this basin, 5 m below the Calcaire de Vitrolles Formation; (2) a gradual δ¹³C increase through the middle upper Paleocene similar in amplitude to that of the marine realm; (3) a short-term negative δ¹³C excursion in the latest Paleocene, as seen within the Calcaire de St. Marc Formation; and (4) a slow decrease during the late Paleocene to early Eocene, with a probable hiatus in the sedimentary record. The Provence mammal site of Palette is shown to be stratigraphically younger than the late Paleocene negative δ¹³C excursion.