Impact of Inherited Foreland Relief on Retro-Foreland Basin Architecture

We use a Landscape Evolution Model including flexural isostasy to investigate the influence of inherited foreland relief on the stratigraphic evolution of the retro-foreland domain during mountain building. We show models with four different types of initial relief in the foreland domain: at sea level, elevated (+300 m), a 1 km-deep and 100 km-wide foreland basin associated with either a forebulge at sea level or elevated at +300 m. During the first 10 Myr of simulation, the landscape evolution of the foreland is significantly altered by its inherited bathymetry/topography. The impact is then smoothed out once the foreland slope has stabilized and develops a transverse drainage network. Models record a long-term shallowing-up mega-sequence driven by the increase in sediment production rate in the uplifting range and the decrease in the rate of flexural accommodation space creation in the foreland basin. The initial relief of the foreland domain alters the timing of its transition from the under-filled to the over-filled phase. An initially deep foreland basin is twice as thick as an initially elevated foreland. It records deep marine deposits while a foreland initially at sea level records thin shallow marine and an elevated foreland records continental deposits. The forebulge is buried by continental deposits in an initially elevated foreland while it is buried by marine sediments in other models. Alluvial fans at the foot of the range are more elevated in initially elevated forelands. We discuss our results of modeled stratigraphic architecture in comparison with the Pyrenean, Alpine and Andean retro-foreland basins.