Evolution of the marine stable carbon-isotope record during the early Cretaceous: A focus on the late Hauterivian and Barremian in the Tethyan realm

Abstract

Abstract In order to improve our understanding of the relationships between the late Hauterivian oceanic anoxic Faraoni event, contemporaneous platform drowning along the northern Tethyan margin and global environmental change in general, we established high-resolution δ 13 C and δ 18 O curves for the late Hauterivian and the entire Barremian stage. These data were obtained from whole-rock carbonate samples from the Veveyse de Châtel-Saint-Denis section (Switzerland), the Fiume-Bosso section and the nearby Gorgo a Cerbara section (central Italy), and the Angles section (Barremian stratotype, France). We observe an increase of 0.3‰ in mean δ 13 C values within sediments from the middle Hauterivian Subsaynella sayni ammonite zone to the Hauterivian–Barremian boundary; δ 13 C values remain essentially stable during the early Barremian. During the latest early Barremian and most of the late Barremian, δ 13 C values increase slowly (until the Imerites giraudi zone) and the latest Barremian is characterized by a negative trend in δ 13 C values, with minimal values at the Barremian–Aptian boundary. During the earliest Aptian, δ 13 C mean values start to rise again and attain + 2.25‰. We interpret the evolution of the δ 13 C record as resulting from the interaction between changes in the carbon cycle in the Tethyan basin and the adjacent platforms and continents. In particular, changes towards warmer and more humid conditions on the continent and coeval phases of platform drowning along the northern Tethyan margin may have contributed to enhance the oceanic dissolved inorganic carbon (DIC) reservoir which may have pushed the δ 13 C record towards more negative values and exerted a general attenuation on the δ 13 C record. From this may have come the general change from a heterozoan to a photozoan carbonate platform community, which influenced the evolution in δ 13 C values by increasing the export of aragonite and diminishing export of dissolved organic carbon into the basins.