Oxygen stable isotopes signals of the early Eocene growth of the Pyrenees: implications for steady-state and response time of mountain ranges
- 1University of Geneva, Department of Earth Sciences, Geneva, Switzerland (sebastien.castelltort@unige.ch)
- 2Institut of Earth Sciences, Géopolis, University of Lausanne, 1015 Lausanne, Switzerland
- 3Institute of Earth Surface Dynamics (IDYST), Géopolis, University of Lausanne, 1015 Lausanne, Switzerland
- 4Department of Geosciences, University of Oslo, Sem Sælands vei 1, 0371 Oslo, Norway
- 5Université de Pau et des Pays de l’Adour, LFCR, UMR5150, 64000 Pau, France
- 6TOTAL, CSTJF, 64018, Pau Cedex, France
- 7Department of Earth and Atmospheric Sciences, 3507 Cullen Blvd., University of Houston
- 8INES ParisTech, PSL University, Centre de Géosciences, 35 rue St Honoré, 77305, Fontainebleau, Cedex, France
- 9Department of Earth and Ocean Dynamics, University of Barcelona, C/ Martí i Franquès, s/n, 08028 Barcelona, Spain
- 10Department of Earth and Ocean Dynamics & Geomodels Research Institute, Faculty of Earth Sciences, Universitat de Barcelona, Spain
- 11Freie Universität Berlin, Division of Tectonics and Sedimentary Geology, Malteserstr. 74-100, 12249 Berlin, Germany
- 12The Deep Time Institute, P.O. Box 27552, Austin, Texas 78755-7552, USA
- 13Equinor Research Center, 6300 Bridge Point Parkway, Building 2, Suite 100, Austin, Texas, USA
The topographic history of an orogen results from the interactions of climate and tectonics, and it can be reconstructed from the sedimentary record of its peripheral basins. Previous tectonostratigraphic studies, including flexural models, and sparse stable oxygen and carbon isotope data from the South-Pyrenean foreland basin suggest that a major period of topographic growth occurred in the late Paleocene-early Eocene. To further test this hypothesis, we present a stack of 658 stable isotope measurements on whole-rock marine carbonate mudstone from a 4800-m-thick composite sedimentary succession which provides a 12 Ma continuous record of environmental conditions during the early to middle Eocene (54 to 42 Ma). From the base of this record (at 54 Ma), oxygen isotopes (δ18O values) show a faster decrease rate than the coeval global negative excursion associated with the Early Eocene Climatic Optimum (EECO). This local alteration of the global δ18O signal indicates that topographic growth during this period, associated with significant tectonic activity, perturbed the oxygen isotopic composition of foreland waters. Thus, our data suggest that significant topographic uplift of the Pyrenean orogen started from at least 54 Ma and continued until ca. 49 Ma, reaching the maximum elevations of 2000±500m in this phase from previous isotope and flexural studies. In addition, our record shows that the long-term carbon stable isotope composition during this period remained relatively stable with no similarity to the global bell-shaped long-term trend of the EECO. This is consistent with the restricted physiography of the South-Pyrenean foreland basin, mainly influenced by local sedimentary and water inputs. Overall, the Pyrenean topographic growth from the Late Cretaceous to the Miocene displays several growth stages that seem to be primarily determined by episodes of an increased rate of tectonic plate convergence. The duration of these growth stages (several millions of years) is possible documentation of the response time of mountain ranges to tectonic perturbations. The results of this work, therefore, demonstrate that stable isotope measurements on whole-rock sediments in foreland basins can provide key information for tectono-climatic and topographic reconstructions of mountain ranges.
How to cite: Castelltort, S., Honegger, L., Adatte, T., Spangenberg, J. E., Poyatos-More, M., Ortiz, A., Curry, M. E., Huyghe, D., Puigdefebregas, C., Garces, M., Vinyoles, A., Valero, L., Laeuchli, C., Nowak, A., Fildani, A., and Clark, J. D.: Oxygen stable isotopes signals of the early Eocene growth of the Pyrenees: implications for steady-state and response time of mountain ranges, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1771, https://doi.org/10.5194/egusphere-egu22-1771, 2022.
