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Thermochronological evidence of early orogenesis, Eastern Pyrenees, France

Ternois, S. ; Odlum, M. ; Ford, M. ; Pik, R. ; Stockli, D. ; Tibari, B. ; Vacherat, A. ; Bernard, V., Tectonics

Thermochronological evidence of early orogenesis, Eastern Pyrenees, France

Ternois, S. ; Odlum, M. ; Ford, M. ; Pik, R. ; Stockli, D. ; Tibari, B. ; Vacherat, A. ; Bernard, V.,

Tectonics, 2019, 38, 1308-1336

Abstract :

The Pyrenean orogen was generated from late Santonian–early Campanian to middle Miocene by N‐S con-vergence of the Iberian and European plates (Choukroune, 1989 ; Muñoz, 1992 ; Macchiavelli et al., 2017).External orogenic zones and foreland basins record two distinct periods of low but accelerating tectonicshortening and subsidence, latest Santonian–Danian and Thanetian–Oligocene, separated by a quiet (verylow to near‐zero subsidence) period during the Paleocene (Ford et al., 2016). These two periods arerecognized to be synorogenic and mark two phases of convergence, the second generally recorded asEocene–Oligocene in low‐temperature thermochronology studies. Significantly, the orogen’s three‐phaseconvergence history does not correspond to behavior predicted by foreland dynamic models (Naylor &Sinclair, 2008 ; Sinclair et al., 2005 ; Sinclair & Naylor, 2012). While the evolution of crustal thickening, ther-micity, orogen relief, and erosion during the main Eocene–Oligocene collisional phase are well studied andshow a clear link to foreland basin dynamics (Fillon et al., 2013 ; Sinclair, 2011), the early Pyrenean history ofconvergence and the subsequent phase of quiescence are poorly constrained. In particular, there are few dataon the thermal and dynamic behavior of the orogen during the earliest phase of Pyrenean convergence. Therecord of early orogenesis is best observed in the retrowedge where shortening and translation values are low(Naylor & Sinclair, 2008) and where the main Aptian–Cenomanian rifting phase is preserved. In this paperwe present new zircon and apatite (U‐Th‐Sm)/He (ZHe and AHe, respectively) data from an externalPaleozoic crustal block, Agly‐Salvezines (Figures 1 and 2), in the eastern Pyrenean retrowedge. By integrat-ing these data with new and published geological data, we address the following questions : Can we recog-nize a thermal signature for the onset of Pyrenean convergence and for Paleocene quiescence ? Are earlycrustal thermal events contemporaneous with early foreland tectonic events, or is there a lag time betweenthese two phenomena ? Can we distinguish an early orogenic thermal signature from other thermal eventssuch as those associated with preceding rifting or later collision ?

Voir en ligne : https://doi.org/10.1029/2018TC005254




publié mercredi 15 janvier 2020