Impact of Inherited Geometries on Syn-orogenic Foreland Basin Architecture

We use a Landscape Evolution Model (FastScape S2S) to explore the impact of inherited topography in the foreland domain of a rising mountain range on its stratigraphic architecture and sediment accumulation history, inspired by the northern Pyrenean foreland. We simulate an uplifting half mountain range, its foreland basin and forebulge, and beyond, an open marine domain. We ran models with 4 different initial reliefs in the foreland domain: an initially flat foreland domain at sea-level, an elevated flat continental foreland (+300 m), a pre-existing 1 km-deep and 100 km-wide bathymetry at the location of the future foreland basin associated with a forebulge domain either at sea-level or elevated at +300m. All models show a prograding mega-sequence associated with building of mountain topography and development of the flexural foreland basin and forebulge, coalescence of alluvial fans at the foot of the range, progressive continentalization of the foreland domain, and burial of the forebulge. An initially elevated foreland domain ultimately produces a thinner foreland basin while an initially deep foreland basin produces a thicker one. After 10-13 Myr, the initial relief of foreland domain is smoothed out and the landscape does not exhibit a record of pre-existing relief. In contrast, the stratigraphic architecture of the foreland basin allows to trace inherited relief with deep marine sediments in the initially deep foreland basin, marine sediments onlapping and then burying the forebulge initially at sea-level, and continental sediments onlapping and burying the initially elevated foreland domain. We compare these interpretations to the Pyrenean retro-foreland.