Morphotectonic Evolution of Passive Margins Undergoing Active Surface Processes: Large‐Scale Experiments Using Numerical Models

Abstract

Extension of the continental lithosphere can lead to the formation of rifted margins with contrasting tectonic and geomorphologic characteristics. Many of these characteristics depend on the manner extension spatially distributed. Here we investigate the feedback between tectonics and the transfer of material at the surface resulting from erosion, transport, and sedimentation and discuss how they influence the rifting process. We use large-scale (1, 200 × 600 km), high-resolution (1 km) numerical experiments coupling a 2-D upper-mantle-scale thermo-mechanical model with a planform 2-D surface processes model. We test the sensitivity of the coupled models to varying crust-lithospheric rheology and erosional efficiency. We confirm that the development and long-term support of topography is dependent on the strength of the coupling between the crust and the mantle lithosphere. Strong coupling promotes high topography as the integrated strength of the lithosphere is sufficient to support the additional stress. Weak coupling results in the stress being relaxed via viscous flow in the middle/lower crust and leads to more subdued topography. Erosion and transport of sediment modulates this behavior but has only minor effect on the overall structure of the rift. High erosion efficiency counters the development of high topography and creates complex landscape morphologies while low erosion efficiency allows for longer standing high topography and results in more simple landscape morphologies. The transfer of mass between the continent and the basin alters the stress field at the onshore-offshore transition and facilitates the development of faults, increasing their offsets and keeping them active over a longer period.Our understanding of the coupling between surface processes and tectonics has developed primarily for convergent orogens (e.g.

Long‐Term Coupling and Feedback Between Tectonics and Surface Processes During Non‐Volcanic Rifted Margin Formation

“…Drainage divide migration (Goren et al, 2014;Braun, 2018) and average topography by river incision (Willett, 2010) could also be modeled with analytical solutions. However, sensitivity tests using a 2-D tectonic model coupled to a 2-D plan form surface process model indicate very similar behavior (Beucher & Huismans, 2016). The model uses a viscoplastic rheology and does not include elasticity.…”

Evolution of rift systems and their fault networks in response to surface processes

“…Topographic erosion and sediment deposition modify Earth's surface through time, changing upper crustal temperatures and affecting crustal pressure conditions through sediment loads (e.g., Olive et al, 2014). The change in loading is an important factor for the evolution of individual faults, where mass redistribution from the uplifted and eroding footwall to the subsiding depositional hanging wall aids strain localization (Maniatis et al, 2009) and prolongs fault activity (Andrés-Martínez et al, 2019;Theunissen and Huismans, 2019;Beucher and Huismans, 2020). Similarly, sedimentation promotes rift migration by enhancing hyperextension of the crust and possibly delays continental breakup (Buiter, 2021).…”

“…Similarly, sedimentation promotes rift migration by enhancing hyperextension of the crust and possibly delays continental breakup (Buiter, 2021). Previous studies have used 2D numerical models to investigate the interplay between surface processes and rift evolution (Andrés-Martínez et al, 2019;Theunissen and Huismans, 2019;Beucher and Huismans, 2020;Pérez-Gussinyé et al, 2020). These studies take a qualitative look at changes to rift system evolution, but do not quantitatively analyze variations in fault properties over time.…”

Influence of Surface Processes on Postrift Faulting During Divergent Margins Evolution

“…The authors showed the feedback between erosion and sedimentation of the surface, ductile flow of lower crust, and the flexural response of the lithosphere. Following this work, other models showed the importance of surface processes affecting the thermal and, hence, rheological structure of the lithosphere (Andrés‐Martínez et al., 2019; Beucher & Huismans, 2020; Pérez‐Gussinyé et al., 2020), even influencing the magmatic activity (Sternai, 2020). Recently, Theunissen and Huismans (2019) identified feedbacks between erosion and deposition and tectonic processes on structural style of rift and divergent margin formation due to the efficiency of surface processes.…”

“…The denudation on the top of the model was simulated by the imposition of a prescribed erosion rate variable in space and time. Other procedures can be adopted, like the assumption of a diffusion equation or a power law equation to simulate surface processes (e.g., Andrés‐Martínez et al., 2019) or coupling with LEM codes (e.g., Beucher & Huismans, 2020). Here, we adopted the prescribed erosion rate to have control on the timing and extent of the erosion, facilitating the comparison of the different numerical scenarios with the same amount of escarpment retreat.…”