CONVERGENCE

OROGEN – SOURCE TO SINK – FLUIDS

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Sébastien TERNOIS

Reconstruction de la dynamique précoce d’un orogène
Mise en évidence de la transition rifting-collision dans le système est-pyrénéen (France) par la géo-thermochronologie

Supervisors:
Raphaël PIK (CRPG), Mary FORD (CRPG)

Major Results

  1. Crustal section sequential restoration integrating new zircon He data demonstrates that tectonic processes alone can generate rapid cooling during early orogenesis.
  2. Brandnew laser zircon He-U/Pb data highlight the dominant role of rift inheritance into early orogenesis and show fairly instantaneous erosional exhumation response to the onset of convergence.

Abstract

By conducting a geo-thermochronometric study of the easternmost, inverted hyperextended Aptian-Cenomanian rift system and the adjacent early retroforeland, this thesis work aims to describe the evolution of a distal rifted margin during the first stages of convergence, to quantify the associated source-to-sink processes and to provide temporal and paleogeographic constraints regarding the creation of the very first Pyrenean reliefs resulting from inversion of the margin.

 

This work provides new evidence for intimate coupling between the mountain belt and its foreland basin(s) during earliest convergence. This also demonstrates the power of laser (U-Th)/He thermochronometry in both distinguishing closely spaced thermal signatures (<30 Ma) and inferring provenance (when combined with geochronometry) with higher temporal and statistical resolution.
Zircon He age-eU correlations and He age distributions for detrital samples from the eastern Pyrenean retro-foreland basin (Ternois et al., submitted to Basin Research) and bedrock samples from the inverted distal European margin of the Cretaceous rift system (Ternois et al., 2019).
The results obtained with the newly developed laser double dating technique reveal a marked increase in denudation rates and accelerating unroofing of thermally reset rifted Pyrenean crust soon after the onset of convergence. They pinpoint processes at play during the very first phases of convergence.

PhD Thesis: Reconstruction de la dynamique précoce d’un orogène – Mise en évidence de la transition rift-collision dans le système est-pyrénéen (France) par la géo-thermochronologie

PhD Thesis: Reconstruction de la dynamique précoce d’un orogène – Mise en évidence de la transition rift-collision dans le système est-pyrénéen (France) par la géo-thermochronologie

Ternois, S.. Reconstruction de la dynamique précoce d’un orogène – Mise en évidence de la transition rift-collision dans le système est-pyrénéen (France) par la géo-thermochronologie. Sciences de la Terre et de l’Univers, environnement. CRPG-CNRS Université de Lorraine

keywords: Pyrénées, Orogène collisionnel, Rétro-prisme précoce, Rétro-bassin d’avant-pays précoce, Transition rifting-collision, Héritage, Provenance sédimentaire, Géo-thermochronologie, (U-Th)/He, U/Pb, Zircon, Ablation laser, Datation in situ, Pyrenees, Collisional orogen, Early retro-wedge, Early retro-foreland basin, Rift-to-collision transition, Inheritance, Sedimentary provenance, Geo-thermochronology, (U-Th)/He, U/Pb, Zircon, Laser ablation, In situ dating, 551.7, 551.82

DOI: https://docnum.univ-lorraine.fr/public/DDOC_T_2019_0086_TERNOIS.pdf