Stable-isotope chemostratigraphy of Urgonian-type platform carbonates: Time to be cautious?

Tendil, Anthony J.-B.; Frau, Camille; Léonide, Philippe; Fournier, François; Borgomano, Jean R.; Lanteaume, Cyprien; Masse, Jean-Pierre; Rolando, Jean-Paul

Abstract

In recent years, δ13C and δ18O chemostratigraphy has become a powerful tool used to solve controversial results using different biological time markers from shallow-marine carbonate environments and establish long-distance correlations across proximal and distal settings. However, its reliability was recently questioned due to the impact of diagenesis on stable isotope records. The ammonite-calibrated, platform-to-basin transect of the late Barremian–early Aptian Urgonian Provence platform is made particularly relevant to challenge chemostratigraphy-based correlation methods in shallow carbonate series at different scales. The origin, preservation and stratigraphic potential of isotopic signatures are herein discussed along 11 shallow-marine and basinal sections. In the proximal settings of the Provence domain, tight carbonates—either resulting from muddy depositional textures or early cementation—likely preserve original marine signatures. Contrasting observations arise from porous carbonates whose stable isotope signal is heavily affected by micrite recrystallization (i.e., microporosity genesis) during a mid-Cretaceous tectonic uplift event. Locally, the C-isotope signal of microporous Urgonian limestones can be controlled by the vertical distribution of porosity. Although basinal series are more prone to preserve primary geochemical signatures, extreme values for carbon and oxygen isotopes are observed in correspondence with fine-grained bioclastic material input originating from the adjacent platform, following the latest Barremian demise of the rudist-dominated platform. This study suggests that stable isotope chemostratigraphy may not constitute a suitable tool for calibrating and correlating Urgonian shallow-marine series.

Citation

Tendil, A. J., Frau, C., Léonide, P., Fournier, F., Borgomano, J. R., Lanteaume, C., …Rolando, J. (2019). Stable-isotope chemostratigraphy of Urgonian-type platform carbonates: Time to be cautious?. In M. Montenari (Ed.), Stratigraphy & Timescales (165-216). Elsevier. https://doi.org/10.1016/bs.sats.2019.08.001

• Online Publication Date: Nov 9, 2019
• Publication Date: 2019
• Deposit Date: Jun 12, 2023
• Publisher: Elsevier
• Pages: 165-216
• Series Title: Case Studies in Isotope Stratigraphy
• Series ISSN: 2468-5178
• Book Title: Stratigraphy & Timescales
• Chapter Number: 5
• ISBN: 978-0-12-817552-1
• DOI: https://doi.org/10.1016/bs.sats.2019.08.001