Rift-to-collision transition recorded by tectonothermal evolution of the northern Pyrenees

Abstract

The impact of rift-related processes on tectonic and thermal evolution of collisional orogens is poorly documented. Here, we study the northern Pyrenees, a region that has preserved a geological record of the transition from rifting to collision. Using modeling of new low-temperature thermochronological data, including fission track and (U-Th)/He on apatite and zircon, we propose a temporal reconstruction of the inversion of the European rifted margin. Our data confirm that rifting and related cooling started in the Late Paleozoic-Triassic. Throughout the Jurassic and Early Cretaceous the European margin recorded slow heating during postrift subdsidence. Modeling of thermochronological data allows distinguishing subsidence and denudation controlled by south dipping normal faults in granitic massifs that reflect a second episode of crustal thinning at 130-110 Ma. Following onset of convergence at 83 Ma, shortening accumulated into the weak and hot Albian-Cenomanian rift basins floored by both hyperextended continental crust and exhumed subcontinental mantle. The lack of cooling during this initial stage of convergence is explained by the persistence of a high geothermal gradient. The onset of exhumation-related cooling is recognized in the whole Pyrenean region at 50-35 Ma. This timing reveals that the main phase of mountain building started when hyperextended rift basins closed and collision between proximal domains of the rifted margin occurred.

Thermochronological Evidence of Early Orogenesis, Eastern Pyrenees, France

“…Similar age variability to that in our ZHe data set is reported in other data sets from the Pyrenees and from other similar orogenic settings (e.g., Guenthner et al, , , ; Vacherat et al, , ). It has been demonstrated that this results from the inability of a single set of kinematic parameters for He diffusion to describe the natural thermochronometric behavior of zircon (Cherniak et al, ; Guenthner et al, ; Ketcham et al, ; Reiners et al, , ).…”

“…Extensive low‐temperature thermochronology studies in the Pyrenees over the last 20 years have produced a world‐class data set to constrain crustal thermal behavior during orogenesis (Bosch et al, ; Hart et al, ; Labaume et al, ; Mouthereau et al, , and references therein; Rushlow et al, ; Thomson et al, ; Vacherat et al, , ). Bedrock low‐temperature thermochronology (AHe and apatite fission track [AFT]) data from the Axial Zone and the basement massifs in the central North Pyrenean Zone record only the Eocene–Oligocene (50–20 Ma) main collision cooling history, younging from east to west and from north to south (Mouthereau et al, ; Whitchurch et al, ).…”

“…On the other hand, the Aptian–Cenomanian rifting generated a major thermal pulse that had not reequilibrated before the onset of convergence some 10 myrs later (Angrand et al, ). This inherited thermal perturbation may have been present during the first 30–35 myrs of orogenesis (Angrand et al, ; Vacherat et al, ), maintaining temperatures during early orogenesis above the sensitivity limit of low‐temperature thermochronometers (40–300 °C; e.g., Carrapa, 2010; Peyton & Carrapa, ) and thus delaying any cooling record until the main Eocene collision (Vacherat et al, ). However, previous limited low‐temperature thermochronology data (Yelland, ) indicate that the massifs at the eastern end of the external Pyrenean orogenic system, Agly‐Salvezines, record a Campanian–Maastrichtian cooling signal, synchronous with the first period of accelerating subsidence in the retroforeland (Ford et al, ).…”

“…However, previous limited low‐temperature thermochronology data (Yelland, ) indicate that the massifs at the eastern end of the external Pyrenean orogenic system, Agly‐Salvezines, record a Campanian–Maastrichtian cooling signal, synchronous with the first period of accelerating subsidence in the retroforeland (Ford et al, ). This signature is absent in more proximal crystalline massifs further west, which only record Eocene exhumation (e.g., Vacherat et al, ), with the exception of the Labourd‐Ursuya Massif at the extreme western end of the orogen (Figure ; Yelland, ; Vacherat et al, ). As paleotemperature data obtained by Raman spectroscopy on carbonaceous material (RSCM; Clerc et al, ; Chelalou et al, , and references therein) and radiometric data (Clerc et al, , and references therein) for Mesozoic sediments suggest higher postrift cooling rates from end of rifting to the onset of convergence in the eastern Pyrenean retrowedge, we can expect paleotemperatures at the onset of orogenesis to be lower in this region.…”

Unraveling the Mesozoic and Cenozoic Tectonothermal Evolution of the Eastern Basque‐Cantabrian Zone–Western Pyrenees by Low‐Temperature Thermochronology

“…(b) Apatite fission track (AFT) data from northern Spain and southern France. Squares are the AFT ages obtained in this work and circles are AFT ages from the literature (Beamud et al, ; Bosch et al, ; Carrière, ; Del Rio et al, ; Fillon et al, , ; Fillon & van der Beek, ; Fitzgerald et al, ; Gibson et al, ; Grobe et al, , ; Jolivet et al, ; Juez‐Larré & Andriessen, ; Labaume, Meresse, Jolivet, & Teixell, ; Labaume, Meresse, Jolivet, Teixell, & Lahfid, ; Martín‐González et al, ; Maurel et al, ; Metcalf et al, ; Morris et al, ; Mouthereau et al, ; Pérez‐Arlucea et al, ; Rahl et al, ; Rat et al, ; Rushlow et al, ; Sinclair et al, ; Vacherat et al, , ; Yelland, ).…”