1. Quantifying incision rates since the early Miocene using terrestrial cosmogenic nuclides into caves: methodological issues, solutions and expectations
- Author
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Sartégou, Amandine, BRAUCHER, Regis, Bourles, D.L., Blard, Pierre-Henri, Zimmermann, Laurent, Tibari, Bouchaib, Sartégou, Amandine, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Histoire naturelle de l'Homme préhistorique (HNHP), Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Université de Lorraine (UL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD)
- Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics ,[SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology ,[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry ,[SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry ,[SDU.STU.TE] Sciences of the Universe [physics]/Earth Sciences/Tectonics ,[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology - Abstract
International audience; The ability of discriminating the various forcing parameters controlling the growth of mountain ranges depends on the knowledge of the deformation, exhumation and sedimentation chronologies and on accurate constraints on the orogen geometry necessary to quantify accretion and erosion fluxes. The Pyrenees, an intraplate collision range, built by the shortening of continental thinned margins during the convergence between Iberia and Eurasia lasting from Late Cretaceous to Early Miocene, are a particularly well-suited study area to examine the coupling and retroactions between climate and tectonics. Indeed, consisting in a doubly vergent asymmetric orogenic wedge, the northeastern foreland basin underwent particular conditions from the Miocene to the Pliocene due to the closure of all oceanic connections resulting from the continuing convergence between Iberia and Eurasia. In addition, the orogenic growth and its sedimentary evolution occurred during the Cenozoic climatic cooling.To investigate these retroactions, alluvium-filled horizontal epiphreatic passages in limestone karstic networks supposedly recording the transient positions of former local base levels during the process of valley deepening were studied. The results obtained applying various suitable geochronological methods (26Al/10Be, 10Be/21Ne, ESR and OSL on quartz) on intrakarstic alluvial deposits of 61 caves from three valleys of the central and eastern Pyrenees, as well as on a recent analogue comprising an active branch, will be presented. In the Pyrenean context and under particular conditions, these burial duration methodologies allow deciphering the deepening history of the valleys over the long term (~ 16-14 Ma). However, in this orogenic area, some issues have been identified: the density of sub-horizontal levels on an altimetric range and their vertical connections, the low tectonic activity during the post-orogenic evolution, the Mediterranean eustatic variations, the ancient glaciation phases, or storage in the watershed may lead to networks filling stories more complex than expected. In some cases, it may be difficult to evaluate the 26Al/10Be ratio associated to the sediments entering the caves or at the time of their deposit (mixing with old deposits). We will show that most of these issues can be solved by conducting small ancillary studies and taking precautions when sampling or treating samples.
- Published
- 2018