Astrochronology of the Valanginian Stage from GSSP Candidates and Hypostratotype
The Valanginian Stage currently displays no radiometric age, which severely hampers palaeoceanographic reconstructions for this time interval. An astrochronology of the Valanginian Stage using the stable 405-kyr eccentricity cycle was performed on biostratigraphically well-calibrated standard sections from the Vocontian Basin (southeastern France). High-resolution gamma-ray spectrometry signals were obtained from orbitally driven marl–limestone alternations from five sections in the basin, and they display the same long-term trends. The spectral analyses present the pervasive record of the 405-kyr eccentricity cycle together with precession, obliquity, and 2.4-Myr eccentricity. Based on the identification of the 405-kyr eccentricity cycle, the duration of the Valanginian Stage is assessed at 5.08 Myr. Since the Weissert Event appears to be ~3 Myr older than the onset of the Paraná–Etendeka Large Igneous Province activity, a link between these events is unlikely. We therefore propose, following Gröcke et al. (2005) and Westermann et al. (2010), that continental organic carbon storage and carbonate platform demise are responsible for the onset of the δ13C positive excursion. In addition, a stronger obliquity control appears in the O. (O.) nicklesi and C. furcillata subzones. This may be linked to the limited production of polar ice suggested for this time interval.
KeywordsValanginian Astrochronology Gamma-ray spectrometry Weissert event Paraná–Etendeka
- Giraud, F. Beaufort, L. Cotillon, P. (1995). Periodicities of carbonate cycles in the valanginian of the vocontian trough: A strong obliquity control. In M. R. House, A. S. Gale (Eds.), Orbital forcing time scales and cyclostratigraphy (Vol. 85) pp 143–164. London: Geology Society Special Publication.CrossRefGoogle Scholar
- Gréselle, B. (2007). Impact des variations paléoclimatiques sur la sédimentation carbonatée au valanginien (PhD Thèse, Université Claude Bernard Lyon 1. 2007) p.337 (unpublished).Google Scholar
- McArthur, J. M., Janssen, N. M. M., Reboulet, S., Leng, M. J., Thirwall, M. F., & van de Schootbrugge, B. (2007). Palaeotemperatures, polar ice-volume, and isotope stratigraphy (Mg/Ca, δ18O, δ13C, 87Sr/86Sr): The early cretaceous (berriasian, valanginian, hauterivian). Palaeogeography Palaeoecology,248(3–4), 391–410.CrossRefGoogle Scholar
- Sprovieri, S., Coccioni, R., Lirer, F., Pelosi, N., & Lozar, F. (2006). Orbital tuning of a lower Cretaceous composite record (Maiolica Formation, central Italy). Paleoceanography,21(4), PA4212.Google Scholar