The Tectonostratigraphic Expression of Slab Breakoff in Foreland Basins: Insights From 2D Forward Stratigraphic Modeling

Changes in foreland basin architecture have been attributed to slab breakoff based on qualitative assessments of geological data. However, this cause-effect relationship has not been evaluated quantitatively. In this contribution, we use a one-way coupling approach between 2D thermomechanical models of slab breakoff and 2D stratigraphic forward models of a pro-foreland basin. This allows a quantitative investigation of the first order tectonostratigraphic signal from slab breakoff in a foreland basin while isolating it from other processes controlling the basin evolution. We investigate the effects of slab breakoff on foreland basin evolution by varying the (a) initial subduction angle and (b) mantle viscosity. Furthermore, we assess whether eustacy can mask the stratigraphic signal from slab breakoff by introducing third-order eustatic cycles. Results highlight that both the final phase of slab necking and subsequent breakoff generally yield higher uplift rates of both the foreland basin (between 0.09 and 25 km/Myr) and mountain range (between 0.13 and 30 km/Myr) for successively steeper slabs and decreased mantle viscosity. In turn, breakoff causes a pulse in sediment supply to the foreland (up to 2.6E10 m3/Myr) due to mountain range uplift. ... mehrIn the models, eustacy has no significant effect on preserving the stratigraphic signal from slab breakoff and the induced underfill to overfill transition. Increasing mantle viscosity promotes a prolonged necking phase that imposes a long-lasting, but weak uplift and related increase in sediment supply. Lastly, first-order features induced by slab breakoff observed on synthetic seismic profiles of our models bear resemblance to reflection seismic data from the Austrian Molasse Basin, where slab breakoff has been suggested to have influenced the basin evolution.