Retro-wedge foreland basin evolution along the ECORS line, eastern Pyrenees, France

Abstract

International audienceThe eastern Aquitaine basin and North Pyrenean Zone show many characteristics of retro-wedge models. However,they differ significantly in that slow subsidence and low deformation continued throughout orogenesis so that growth andsteady-state phases cannot be distinguished. We show that the eastern Pyrenees record two clear phases of convergence andprobably never attained steady state. Analysis of the Aquitaine retro-foreland basin along the Ariège ECORS deep seismic line,eastern French Pyrenees, integrates a new litho- and chronostratigraphy, subsidence analysis, low-temperature thermochronologydata, new interpretations of seismic lines and a balanced cross-section. Within an overall regression, twoshallowing-up cycles (Latest Santonian–Danian, Thanetian–Oligocene) record slow tectonic subsidence of the easternAquitaine basin separated by a quiet period. Continuing thick-skinned shortening was low to moderate. The early marine basin,generated by loading of the weak, extended margin, was supplied axially from an unknown eastern edifice while the youngPyrenean orogeny to the south remained submerged. During the quiet period of ultra-slow subsidence, no basin migration andnegligible sediment supply, continental conditions characterized the eastern orogen. The second marine transgression wasquickly followed by continental conditions. The basin was supplied by the now emerging Pyrenean orogen and continued tosubside until Miocene time

Crustal structure and evolution of the Pyrenean-Cantabrian belt: A review and new interpretations from recent concepts and data

“…16A follows the trace of the ECORS-Pyrenees profile across the eastcentral Pyrenees, crossing the North Pyrenean Zone in Ariège, the Axial Zone and the southern Pyrenees along the Noguera Pallaresa valley. Descriptions and references of the surface geology can be found in Baby et al (1988), Déramond et al (1988), Muñoz (1992), Berástegui et al (1993), Vergés (1993), Ford et al (2016) and Cochelin et al (2017). The deep structure was surveyed by the ECORS-Pyrenees and PYROPE E geophysical profiles Chevrot et al, 2015) (Figs.…”

Thermochronological Evidence of Early Orogenesis, Eastern Pyrenees, France

“…This suggests that an active orogenic zone existed further east for which two early cooling events are probably recorded by limited detrital low‐temperature thermochronology data (95–135 and 60–80 Ma; Filleaudeau et al, ; Whitchurch et al, ; 85–110 and 60–85 Ma; Mouthereau et al, ; Vacherat et al, ). The early Pyrenean orogen itself (Central Pyrenees) probably formed a low relief or even submarine edifice (Ford et al, ; Vacherat et al, ), with slow exhumation (0.2 km/Myr) and little sediment yield until the late Eocene (Fillon & van der Beek, ; Fitzgerald et al, ). We would therefore expect that any sediments sourced from this area would be restricted to the upper, thermally non‐reset levels of the crust.…”

“…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, ). 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, ).…”

“…The Pyrenean orogen was generated from late Santonian–early Campanian to middle Miocene by N‐S convergence of the Iberian and European plates (Choukroune, ; Muñoz, ; Macchiavelli et al, ). External orogenic zones and foreland basins record two distinct periods of low but accelerating tectonic shortening and subsidence, latest Santonian–Danian and Thanetian–Oligocene, separated by a quiet (very low to near‐zero subsidence) period during the Paleocene (Ford et al, ). These two periods are recognized to be synorogenic and mark two phases of convergence, the second generally recorded as Eocene–Oligocene in low‐temperature thermochronology studies.…”

“…Campanian‐to‐Maastrichtian successions of the early Pyrenean foreland basins record sediment supply from a main eastern source area (Bilotte, ; Monod, ; Plaziat, ), which has since been destroyed by the Oligocene–Miocene opening of the Gulf of Lion (Séranne, ; Gunnell et al, , ). The early orogenic wedge supplied little or no sediment at this time and therefore was of low relief, probably largely submarine (Ford et al, ). During the Eocene main collision, the growth of major orogen relief then migrated from east to west (Whitchurch et al, , and references therein).…”