Thomas BERNARD

Post-orogenic sediment flux to continental margins: Miocene erosion and sediment yield from the Pyrenees

Supervisors:
SINCLAIR Hugh
University of Edinburgh

Major Results

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.

Abstract

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 is investigated using a box model to explore the syn- to post-orogenic evolution of foreland basin/thrust wedge systems. Numerical modelling of a thrust wedge/foreland basin system predicts that the late syn‐ to post‐orogenic transition is associated with an important increase in the elevation of the foreland basin (mean elevation increase of ~ 250 m taking place over ~ 8 Ma following the onset of post‐orogenesis (i.e. 23 to ~ 15 Ma)). The middle Miocene depositional surface made of large alluvial fans results from an early post‐orogenic aggradation phase.

It draped the Sub‐Pyrenean zone and North Pyrenean Thrust Belt at high elevation (i.e. up to 600–700 m). Conglomerates preserved there, which is ~300 m above the present mountain front in the northern Pyrenees record an age of ca. 12 Ma, approximately 8 Myrs younger than the last evidence of crustal thickening in the wedge. Using the model, this post-orogenic sediment drape can be 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 basin subsidence.

Syn- to post-orogenic bloc-diagrams evolution of foreland basin/thrust wedge systems. Numerical modelling of a thrust wedge/foreland basin system predicts that the late syn‐ to post‐orogenic transition is associated with an important increase in the elevation of the foreland basin (mean elevation increase of ~ 250 m taking place over ~ 8 Ma following the onset of post‐orogenesis (i.e. 23 to ~ 15 Ma)).

PhD Thesis: Post-orogenic sediment flux to continental margins: Miocene erosion and sediment yield from the Pyrenees

Thomas Bernard. Post-orogenic sediment flux to continental margins: Miocene erosion and sediment yield from the Pyrenees. University of Edinburgh, 2019.

keywords: Central Pyrenees; Exhumation; Post-orogenic; Foreland basin rebound; Landscape numerical modelling, Topographic analyses

DOI:

Post-orogenic sediment drape of mountain ranges: An example from the Northern Pyrenees explained using a box model

Bernard, T., Naylor, M., Christophoul, F., Ford, M. (2020) : Post-orogenic sediment drape in the Northern Pyrenees explained using a box model.

keywords: isostatic rebound, post‐orogenic, foreland sediment influx, continental sedimentation

DOI: https://doi.org/10.1111/bre.12457

Lithological control on the post-orogenic topography and erosion history of the Pyrenees

Bernard, T., Sinclair, H. D., Gailleton, B., Mudd, S. M., & Ford, M. (2019). Lithological control on the post‐orogenic topography and erosion history of the Pyrenees. Earth and Planetary Science Letters.

keywords: Pyrenees, channel steepness, rock strength, thermal histories, landscape evolution, exhumation

DOI: https://doi.org/10.1016/j.epsl.2019.04.034