Does slab avalanching induced mantle-flow accelerate post-rift subsidence in extensional basins?

• Applicants: Dr. Giridas Maiti; Professorin Dr. Nevena Tomasevic
• Subject Area: Geology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567223075

Extensional basins form through lithospheric stretching, where crustal thinning via normal faulting initially drives rapid basin subsidence (syn-rift stage). This is followed by thermal cooling of the extended lithosphere, leading to passive subsidence with an exponentially decreasing subsidence rate (post-rift stage). However, many extensional basins deviate from this norm, exhibiting accelerated post-rift subsidence that can reach up to 6 km. This cannot be explained by existing widely used models based solely on the amount of lithospheric stretching during the syn-rift stage. Interestingly, basins recording excess post-rift subsidence spatially and temporally correlate with the processes of slab stagnation and slab avalanching at the mantle transition zone. This suggests that heat flow induced by slab stagnation may weaken the overriding lithosphere, while subsequent downwelling mantle flow from slab avalanching may generate dynamic subsidence, contributing to the observed excess post-rift subsidence. However, this is based on deductive reasoning and quantitative assessment of these processes on excess post-rift subsidence is missing. To investigate this, we will employ state-of-the-art thermomechanical numerical simulations that couple geodynamic models of slab avalanching with surface process models, accounting for erosion and sedimentation in basins. This approach will enable us to track the evolution of fault networks and their interactions with sedimentary sequences, as well as the influence of surface processes such as sedimentation and erosion rates, external sediment supply, and relative sea-level fluctuations within and around the basin. This will enable a quantitative assessment of subsidence rates during the syn- and post-rift stages, influenced by slab stagnation and slab avalanching processes. Key outputs, including syn- and post-rift subsidence rates, excess post-rift subsidence magnitude, heat flow, bathymetric changes, and sedimentary sequence thickness, will be directly compared with compiled and reviewed published data from basins that experienced accelerated post-rift subsidence. Finally, by integrating state-of-the-art modeling results with geological and geophysical data, we will assess the role of slab avalanching induced downwelling mantle-flow and surface processes in driving excess post-rift subsidence.

• DFG Programme: Research Grants
• Co-Investigators: Dr. Michael Pons; Professor Dr. Marcel Thielmann