Post‐orogenic sediment drape in the Northern Pyrenees explained using a box model

Abstract

The transition to a post‐orogenic state in mountain ranges has been identified by a change from active subsidence to isostatic rebound of the foreland basin. However, the nature of the interplay between isostatic rebound and sediment supply, and their impact on the topographic evolution of a range and foreland basin during this transition, has not been fully investigated. Here, we use a box model to explore the syn‐ to post‐orogenic evolution of foreland basin/thrust wedge systems. Using a set of parameter values that approximate the northern Pyrenees and the neighbouring Aquitaine foreland basin, we evaluate the controls on sediment drape over the frontal parts of the retro‐wedge following cessation of crustal thickening. Conglomerates preserved at approximately 600‐m elevation, which is ~ 300 m above the present mountain front in the northern Pyrenees are ca. 12 Ma, approximately 10 Myrs younger than the last evidence of crustal thickening in the wedge. Using the model, this post‐orogenic sediment drape is explained by the combination of a sustained, high sediment influx from the range into the basin relative to the efflux out of the basin, combined with cessation of the generation of accommodation space through basin subsidence. Post‐orogenic sediment drape is considered a generic process that is likely to be responsible for elevated low‐gradient surfaces and preserved remnants of continental sedimentation draping the outer margins of the northern Pyrenean thrust wedge.

Geodynamic evolution of a wide plate boundary in the Western Mediterranean, near-fieldversusfar-field interactions

“…This early setting of compressional conditions is also recorded in the Betics (Vergés and Fernàndez, 2012;Daudet et al, 2020). The post-orogenic phase, not to be confused with post-orogenic extension that formed the Gulf of Lion rift, started at around 23 Ma and lasted until ∼12 Ma with the draping of large alluvial fans at high altitude on top of the northern and southern wedges (Babault et al, 2005;Bernard et al, 2020). Shortening was accommodated by a series of north-dipping and south-dipping thrusts involving the basement in the North Pyrenean Zone and the Axial Zone and mainly the cover in the South Pyrenean Zone above the Triassic evaporites decollement (Choukroune, 1989;Choukroune et al, 1990;Mouthereau et al, 2014;Teixell et al, 2018;Espurt et al, 2019;Grool et al, 2019;Jourdon et al, 2020).…”

Thermal record of the building of an orogen in the retro‐foreland basin: Insight from basement and detrital thermochronology in the eastern Pyrenees and the north Pyrenean basin (France)

“…Ortiz et al (2020) interpret the Chattian evolution as the transition from orogenic to post-orogenic conditions. Bernard et al (2021) propose a similar pattern of evolution although with some discrepancy in the ages of turnaround where a rebound of the basin is registered several Ma after the end of the syn-orogenic conditions.…”

“…Bernard et al. (2021) propose a similar pattern of evolution although with some discrepancy in the ages of turnaround where a rebound of the basin is registered several Ma after the end of the syn‐orogenic conditions.…”

“…Bernard et al. (2021) recently modelled the evolution of the Pyrenean topography to explain sediment drapes and HELRS development in northern Pyrenees. They propose that sediment draping, considered as post‐orogenic, occurred through the combination of sustained high sediment flux from the range into the basin, relative to the efflux out of the basin, and the cessation of the generation of accommodation space through basin subsidence by tectonic loading.…”

“…Bernard et al (2021) recently modelled the evolution of the Pyrenean topography to explain sediment drapes and HELRS development in northern Pyrenees. They propose that sediment draping, considered as post-orogenic, occurred through the combination of sustained high sediment fluxF I G U R E 9 Planation surfaces in the Pyrenees from by Bosch, Van Den Driessche, et al (2016) (top) and palaeo-topography of the Oligocene sediments according to low-temperature thermochronology results (bottom) EAGE AL REDA Et AL.…”