- Directeurs : Cécile Gautheron et Jocelyn Barbarand
- Financement BRGM/Total
- Début de thèse : octobre 2016
Main exhumation of the Pyrenean belt as constrained by thermochronological data is diachronous from East (Ypresian) to West (Priabonian to Miocene). This exhumation is partly correlative to the main phase of convergence and active deformations of the forelands. In the northern foreland basin (Aquitain basin), sediment input is partly accommodated by flexure of the basin although gradual installation of a continental sedimentation from east to west starts in the eastern part in Ypresian and traduce a transition from underfilled to overfilled basin. During the beginning of Eocene transition to overfilled condition is progressive as syn-orogenic conglomerates are deposited in the Eastern part of the basin while a drainage network parallel to the main axis of the mountain belt and prograding deltaic sedimentation in the basin are characterized in the central and western part. On the opposite, from Priabonian onwards a generalized, dominantly continental deposition is taking place, mainly formed of lacustrine, fluvial and estuarine deposits. The objective of this thesis is to characterize the transition between these two end members in terms of basin dynamics and sediment routing system. Partly syn-orogenic conglomerates currently termed Poudingues de Palassou are present along the northern flank of the Pyrenean mountains and record the exhumation and denudation of the mountain belt. However their age, stratigraphy and sedimentology and the modalities of the transition to more distal continental deposits and moreover marine facies is poorly constrained. The sources of the terrigenous material, the evolution of the drainage network, the occurrence of sedimentary traps or by pass, occurrence of lag time from denuded reliefs to sedimentation in the basin, and overall characteristics of sedimentary packages (geometry, volume of sediments and associated architecture and facies content) will be the main questions addressed. This characterization of the sink will be correlated to the compilation of the thermochronological data in the orogenic belt already present in the literature paleosurfaces that should be dated during the source to sink project.
The main tasks will be :
Recompose, through sedimentological and basin analysis tools (outcrops of prePriabonian terrigenous deposits, (Poudingues de palassou and lateral equivalents), subsurface data), the geometry and detailed palaeogeography of the Ypresian to Priabonian proximal continental deposits and correlate them with already documented basinal deposits (Serrano, 2001 ; Ortega, PhD ending in December 2016.) ;
Identify the source of the resedimented erosional products in the proximal and basinal areas, through the analysis of clasts in the conglomerates, heavy minerals characterization and geochemistry. – Identify sources and lag times between exhumation and sedimentation in the basin through detrital thermochronology ;
Evaluate the sediment routing system through the recomposition of the different types of drainage network, analysis of granulometric fractioning, and correlation between volumes of exhumed and sedimented rocks. – Comparison with the south Pyrenean basin dynamic.