Impact of lithosphere deformation onstratigraphic architecture of passive marginbasins

National audienceThe aim of this study is to revise our view of the long-term stratigraphictrends of passive margins to include the impact of the coupling betweenthe lithosphere deformation and the surface processes. To do this, wedeveloped a new numerical procedure simulating interactions betweenlithosphere deformation and (un)loading effects of surface processes(erosion/sedimentation) in 3D with a special attention to the stratigraphicarchitecture of the associated sedimentary basins.We first simulatethe syn-rift phase of lithosphere stretching by thermo-mechanical modeling.We then use the resulting lithosphere geometry as input of a 3Dflexural modeling including coupling with surface processes to simulatethe post-rift evolution of the margin. We then use the resulting accumulationand subsidence histories as input of the stratigraphic simulation tomodel the detailed stratigraphic architecture of the basin. We tested thisprocedure using synthetic examples of lithosphere stretching based ondifferent rheologies of the lithosphere (i.e. strength of the lower crust) inthe cases of narrow or ultrawide rifting.We determined the stratigraphicexpression of the conjugate margins and show that they differ in termsof long-term stratigraphic trends, erosion/accumulation and lithologicaldistribution in space and time.In all cases, uplift/subisdence rates decrease with time while the flexurewavelength increases as isotherms are re-equilibrated. Some areas showdisplacement inversion over time from uplift to subsidence (or viceversa).As expected, the amplitude of vertical motion of the wide margincases is very limited with respect to the narrow margin case. Verticalmotions are very asymetric on conjugate margins. Accordingly, thestratigraphic architectures and the sedimentation/erosion patterns of theconjugate simulated margins are significantly different mostly becausethe duration and length of progradation and retrogradation differ. Weevaluated the sensitivity of the simulations to parameters controlling (i)the lithosphere deformation, (ii) the continental drainage erosivity (climate)or (iii) erodability (lithology) as well as (iv) base level (eustasy)