The Topset-Foreset Rollover Does Not Coincide With Real Shoreline Positions in Clinoforms Over Substrate Deformation

Abstract

Shoreline trajectories are migration path lines of topset-foreset rollovers in clinoforms. Stratigraphic trajectory analysis is largely based on its reflection of historical shoreline positions. However, this assumption is valid only when the substrate remains stable. In this study, we conducted numerical simulations and quantitative analyses to investigate the impact of gravity-driven deformation on shoreline trajectories. In a simulation with a rigid substrate, the shoreline trajectory initially moved basinward and then retreated landward, following the theoretical autoretreat in response to steady relative sea level (RSL) rise. In a simulation with a viscous substrate, the occurrence of syn-depositional deformation resulted in a much more complex shoreline trajectory, even with the same sediment supply and sea level rise. Our findings explicitly demonstrate that shoreline trajectory is not only controlled by the sediment supply and RSL change but also substrate deformation. Identifying syn-depositional deformation is critical in reconstructing shoreline evolution and avoiding misinterpretation.