Links Between Faulting, Topography, and Sediment Production During Continental Rifting: Insights From Coupled Surface Process, Thermomechanical Modeling

Abstract

Continental rifts form by extension, and their subsequent evolution depends on the tectonic and climatic boundary conditions. We investigate how faulting, topography, and the evolution of the sediment flux during rifting are affected by these boundary conditions, in particular whether it is possible to correlate tectonic activity, topography, and sediment flux on long timescales (40 Myr). We use a thermomechanical model coupled with a landscape evolution model and present a series of 14 models, testing the sensitivity of the models to crustal strength, extension rate, and fluvial erodibility. The degree of strain localization drives the structural evolution of the modeled rifts: slow extension, high crustal strength, and efficient surface processes promote a high degree of strain localization, resulting in fewer active faults with larger offset. Overall, the magnitude of sediment production correlates with the degree of strain localization. In case of unchanged erosional power and similar amount of extension, systems with slower extension produce more sediment owing to a stronger positive feedback between erosion and fault offset. We observe a characteristic sequence of events, reflecting the morpho‐tectonic evolution of rifts: the highest rock uplift rates are observed before the maximum elevation, and the highest sediment flux postdates the peak in elevation. Our results indicate that for natural systems, the evolution of the sediment flux is a good proxy for the evolution of topography, and that a time lag of 2–5 Myr between the peaks in main tectonic activity and sediment flux can exist.

Evolution of Rift Architecture and Fault Linkage During Continental Rifting: Investigating the Effects of Tectonics and Surface Processes Using Lithosphere‐Scale 3D Coupled Numerical Models

“…Similar to modeling studies in 2D, we observe in three dimensions that the feedback between footwall erosion and hanging wall deposition leads to increased fault offset (Andrés‐Martínez et al., 2019; Maniatis et al., 2009; Neuharth et al., 2022; Olive et al., 2014; Theunissen & Huismans, 2019; L. Wolf, Huismans, Rouby, et al., 2022). In addition, increased erosion extends fault activity and prevents the segmentation of individual faults.…”

“…Both codes are applied in a coupled manner as outlined in the manuscript. The data used for the analyses and figures in the paper are available for all models at https://doi.org/10.6084/m9.figshare.19666074.v2 (L. Wolf, Huismans, Wolf, et al., 2022).…”

Coupling Crustal‐Scale Rift Architecture With Passive Margin Salt Tectonics: A Geodynamic Modeling Approach

“…The models exhibit a decrease in salt thickness and base‐salt relief with increasing pre‐salt sediment thickness and a consequent decrease in the number of diapirs and structural complexity (Figure 8). We note that the rifted margin architecture and fault geometries of these two models differ slightly between each other and reference model M3 owing to the feedback between syn‐rift sedimentation and rifting (cf., Andrés‐Martínez et al., 2019; Theunissen & Huismans, 2019; Wolf et al., 2022).…”

“…Several wide salt-bearing margins worldwide display a similar margin architecture and styles of salt tectonics as well as magnitudes of extension, translation, shortening, and diapirism as our wide margin model M3. Examples include Campos (Figure 1c) (Davison et al, 2012;do Amarante et al, 2021) and northern Santos in Brazil , and Lower Congo and Gabon in West Africa (Epin et al, 2021;Kukla et al, 2018;Rowan, 2014;Unternehr et al, 2010). These margins are ∼200-250 km wide and show significant (∼20 km) updip overburden extension that is balanced seaward by translation and downdip shortening (Figure 1c) (cf., Hudec & Jackson, 2004;Quirk et al, 2012;.…”

“…The viscosity values used in our study cover the range of viscosities expected for salt successions with distinct compositions and small (<10%) proportions of interbedded non-halite lithologies, including anhydrates, carbonates, potassium salts (C. A. L. Rodriguez et al, 2018;Rowan et al, 2019). A linear (Newtonian) viscous salt rheology is a valid approximation based on laboratory experiments of halite deformation by pressure solution (Carter et al, 1993;Spiers et al, 1990;Van Keken et al, 1993), which has been widely used in numerical modeling studies (Albertz & Ings, 2012;Allen & Beaumont, 2016;Gemmer et al, 2004;Goteti et al, 2013;Gradmann & Beaumont, 2017). For simplicity, we focus on presenting and discussing only the left margin of each model as the width and geometry of their conjugates and the overall style of salt tectonics are similar (see Supporting Information S1).…”