Background: Sediment production on Earth is dominated by the erosion of active mountain ranges, hence it seems intuitive that orogenesis should correlate with maximum sediment flux to continental margin deltas. However, active mountain ranges are surrounded by foreland basins that act as sediment traps for the erosional efflux. Model predictions indicate that the majority of sediment is released as orogenic shortening decelerates, leading to post-orogenic rebound of the foreland basin. The erosional products of the mountain range are combined with the sediment eroded from the foreland basins to generate increased sediment flux to continental margins. These important predictions for sediment routing need testing.
Objectives: In the southern Pyrenees, the transition from crustal thickening to post-orogenic decay has been documented using combined structural geology and thermochronology. However, in the northern retrowedge and its associated foreland basin (the Aquitaine Basin), the late to post-orogenic evolution is not understood, and it appears that basin subsidence continued after orogenesis terminated; whether this is the case, and why this might be, are critical to understanding sediment release from the Pyrenean system to surrounding continental margins. This project will quantify the spatial distribution and timing of post-orogenic erosion and sediment production from the key massifs in the mountain range, and from the isostatic rebound of the Aquitaine basin using U-Th/He and fission track (FT) in apatites. These data will test model predictions of mountain belt/foreland basin evolution during post-orogenic decay, using a model which will explore varying flexural rigidities, crustal thickening and thrust topography. The model will be adapted to predict sediment loss out of the system to surrounding continental margins. In addition to the changes in sediment flux, the project will analyse evolving sediment type in terms of grainsize distributions in vertical sections that record the transition from syn- to post-orogenic sedimentation.
Student training: The project will involve: 1) training in U-Th/He in apatites involving running multiple, single grain apatite U-Th/He analyses (Pik, Stuart) and apatite fission track (Persano) integrated into structural models of the retro-wedge (Ford); 2) Numerical modelling of post-orogenic systems (Sinclair, Naylor); 3) Stratigraphic and sedimentological analyses of exposures and subsurface (Sinclair, Christophoul).
Advisory team: Hugh Sinclair (University of Edinburgh, Principal advisor), Mark Naylor (Edinburgh), Mary Ford (CRPG), Raphaël Pik (CRPG), Fin Stuart (SUERC, East Kilbride), Frédéric Christophoul (GET, Toulouse), Cristina Persano (University of Glasgow)
Host Institution: University of Edinburgh
Eligibility: the candidate must have received his/her master degree at the closing date of the call. Knowledge in French language is not required but the candidate should understand that he(she) is expected to acquire basic knowledge of French during their doctoral appointment. All graduate students in all fields of quantitative science are welcome. However, the range of studied topics, and methodologies, requires that the candidate must have some experience in geodynamics, tectonics and basin analyses. Additional knowledge or experience in thermochronology will be welcome.
Application: Applicants are invited to send their motivation letter and CV, with names and contact information with one or two referees to Professor Hugh Sinclair, [email protected]
Closing date for applications: June 2016. Starting date: 1st October 2016.