SOURCE-TO-SINK EVOLUTION OF A SUPRADETACHMENT BASIN UNRAVELED BY DETRITAL APATITE FISSION TRACK ANALYSIS: THE GEDIZ GRABEN (MENDERES MASSIF, WESTERN TURKEY)

International audienceThe Tertiary evolution of the Aquitaine basin (northern Pyrenean foreland) is closely linked tothe Pyrenean orogeny and its northern retrowedge. During the Middle Eocene maximum ofIberia- Eurasia collision (Ypresian- Bartonian) strong denudation of the mountain belt takesplace, partly compensated by the subsidence of the foreland. In the Aquitaine basin this periodis registered by the progressive transition from dominantly marine underfilled sedimentationto continental overfilled sedimentation. In the proximal part of this system, this overfillingleads to a massive, kilometer thick, conglomeratic sedimentation while deltaic sedimentationprogressively fills the basin from east to west.This study focuses on the proximal part of this system in order to characterize (1) the dynamicsof the piedmont sedimentation and its relation to tectonics, climate and denudation ofthe orogen, and (2) the transfer of sediments from the piedmont towards more distal areas, through the definition of types of sedimentary systems and identification of zones of trappingand bypass . Field study of the syn-orogenic Palassou conglomerates and molasses deCarcassonne from Mouthoumet massif to Lavelanet has been coupled with interpretation ofsubsurface (well logs and seismic profiles) in order to characterize the geometries and contentsof these deposits.The Ypresien – Late Bartonian system is organized along two main megasequences:- A continued progradation during Ypresian from deltaic to proximal braided streamand sheet flood deposits. Clasts are mainly composed of meso-cenozoic cover. This progradingtrend accompanies the onset of thrusting in the foreland. The following retrograding trendtakes place during Lutetian with the sedimentation of lacustrine and floodplain deposits withintercalated coarse sheet flood deposits.- The second megasequence displays a major progradation with proximal braidedstream to alluvial fan deposits which traduces uplift and incision of the piedmont. This sequenceregister the first input of material derived from the axial zone.These two sequences display significantly different geometries revealing strong differentcontrols by tectonics and sediment supply and evolving sediment routing. While the first -underfilled-sequence is strongly controlled by the deformation of the foreland, the second one is more widespread with limited control of the deformation and progressive sealing of the structures.Thermochronology as well as refined datations and correlations will complete this early resultsand help linking the dynamics of the Pyrenean orogeny and among all the relative influence oftectonics and climate with the input of sediment and their transfer toward sink areas.The characterization of the transfer of sediments during the syn-orogenic period will be studiedin the framework of the S2S project (a Total- BRGM collaboration). The current results havebeen collected during research programs RGF (BRGM) and Gaia (TIGF/BRGM/AEAG)