EGU2020-8923
https://doi.org/10.5194/egusphere-egu2020-8923
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Astrochronology of the Barremian Stage: implications for the dynamics of the anoxic events in the Early Cretaceous

Mathieu Martinez1, Roque Aguado2, Miguel Company3, Jose Sandoval3, and Luis O'Dogherty4
Mathieu Martinez et al.
  • 1Univ Rennes, CNRS, Géosciences Rennes, UMR 6118, 35000 Rennes, France (mathieu.martinez@univ-rennes1.fr)
  • 2Departamento de Geología y CEACTierra, Universidad de Jaén, Campus Científico-Tecnológico de Linares, 23700 Linares, Spain (raguado@ujaen.es)
  • 3Departamento de Estratigrafía y Paleontología, Universidad de Granada, 18002 Granada, Spain (mcompany@ugr.es; sandoval@ugr.es)
  • 4Departamento Ciencias de la Tierra, Universidad de Cádiz, CASEM, 11510 Puerto Real, Spain (luis.odogherty@uca.es)

Large uncertainties exist on the numerical ages of the stages in the Early Cretaceous which hamper from an accurate reconstruction of the past climate. Recent radio-astrochronologic data suggest to move the ages of the Tithonian to the Hauterivian stages by 3 to 5 Myr toward younger ages (Lena et al., 2019; Aguirre-Urreta et al., 2019). As the numerical ages in the Cenomanian are constrained with radio-astrochronology, this means that the duration of the Barremian to the Albian stages is overestimated. The duration of the Barremian Stage was estimated by bed counting on the assumption of a control by precession and eccentricity cycles (e.g., Bodin et al., 2006). The alternations and bundling can vanish leading to uncertainties in the duration estimates. Here, we provide an astrochronology from the eccentricity cycles based on spectral analyses performed on both magnetic susceptibility and calcium carbonate content series. Two sections are studied here in the Subbetic Domain (SE Spain). They are composed of marl-limestone alternations which reflect humid-arid cycles orbitally-driven. Detailed ammonite and calcareous nannofossil controls allow correlations with other sections in the basin and in the Tethyan Realm. The short and long-eccentricity cycles are identified throughout the Late Hauterivian to the earliest Aptian. The interval around the Hauterivian-Barremian boundary was recovered in a section previously studied for astrochronology and shows that the eccentricity cycles can be correlated to the sections studied here, validating the interpretations. From the record of the 405-kyr eccentricity cycle, the duration of the Barremian Stage is proposed at 4.25 ± 0.13 Myr. Anchoring this duration on previously obtained radio-astrochronology at the end of the Hauterivian, the Barremian Stage started at 125.91 ± 0.06 Ma and ended at 121.67 ± 0.11 Ma. The age of the latest Barremian agrees well with the age of the base of magnetochron M0r calculated from a synthesis of radiometric ages (Olierook et al., 2019). The Faraoni, Mid-Barremian and Taxy episodes show a pacing of 2.34 Myr, suggesting a strong orbital control on the expansion of oceanic anoxic conditions in the Tethys.

References:

Aguirre-Urreta, B., et al., 2019. Gondwana Res., 70, 104–132. https://doi.org/10.1016/j.gr.2019.01.006.

Bodin, S., et al., 2006. Palaeo-3, 235, 245–264. https://doi.org/10.1016/j.palaeo.2005.09.030.

Lena, L., et al., 2019. Solid Earth, 10, 1–14. https://doi.org/10.5194/se-10-1-2019.

Olierook, H.K.H., et al., 2019. Earth-Sci. Rev., 197, 102906. https://doi.org/10.1016/j.earscirev.2019.102906.

How to cite: Martinez, M., Aguado, R., Company, M., Sandoval, J., and O'Dogherty, L.: Astrochronology of the Barremian Stage: implications for the dynamics of the anoxic events in the Early Cretaceous, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8923, https://doi.org/10.5194/egusphere-egu2020-8923, 2020

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Presentation version 1 – uploaded on 27 Apr 2020
  • CC1: Comment on EGU2020-8923, James Ogg, 03 May 2020

    This is a very exciting advance in achieving a cycle-scaled Cretaceous Period, especially for the individual ammonite and other zones within each stage.  Please send me a preprint of your pending paper when it accepted.  Has your group, or another team, been able to apply these detailed methods to the Berriasian ammonite zones, and verified it?  Unfortunately, your Valanginian-Hauterivian-Barremian reference sections for the cyclo-scaled biozones have been unsuccessful for magnetostratigraphy; hence can not be easily applied to determine oceanic spreading rates.  I'd be happy to contribute to that cycle-scaled magnetostratigraphy effort and intercalibrations; perhaps partly using DSDP-ODP studies.  This is very exciting work!  -- Jim Ogg   (jogg@purdue.edu;  Purdue University;  plus also a visiting professor, when it is again healthy to travel, at Wuhan's China Univ. Geosciences).

    • AC1: Reply to CC1, Mathieu Martinez, 04 May 2020

      Dear Jim,

      Many thanks for your very positive feedback! I will send you the paper once it is accepted. Unfortunately, our team has not worked yet on the Berriasian Tethyan ammonite zones. The only ammonite zone we have is the last subzone of the Berriasian (Otopeta). Many thanks for your offer of working together to calibrate the magnetochron using astrochronology. I will be happy to discuss together to see what we can implement.

      All the best,

      Mathieu