Three‐dimensional numerical simulations of crustal systems undergoing orogeny and subjected to surface processes

Abstract

As several modeling studies indicate, the structural expression and dynamic behavior of orogenic mountain belts are dictated not only by their rheological properties or by far-field tectonic motion, but also by the efficiency of erosion and sedimentation acting on its surface. Until recently, numerical investigations have been mainly limited to 2-D studies because of the high computational cost required by 3-D models. Here, we have efficiently coupled the landscape evolution model Cascade with the 3-D thermomechanically coupled tectonics code FANTOM. Details of the coupling algorithms between both codes are given. We present results of numerical experiments designed to study the response of viscous-plastic crustal materials subjected to convergence and to surface processes including both erosion and sedimentation. In particular, we focus on the equilibration of both the tectonic structures and on the surface morphology of the orogen. We show that increasing the efficiency of fluvial erosion increases the frontal thrust angle, which in turn decreases the width of the orogen. In addition, the maximum summit elevation of the orogen during transient evolution is significantly higher in those models showcasing surface processes than those that do not. This illustrates the strong coupling between tectonics and surface processes. We also demonstrate that an along-strike gradient of erosion efficiency can have a major impact upon the landscape morphology and the tectonic structure and deformation of the orogen, in both the across-strike and alongstrike directions. Overall, our results suggest that surface processes, by enhancing localization of deformation, can act as a positive forcing to topographic building.

The role of lateral lithospheric strength heterogeneities in orogenic plateau growth: Insights from 3‐D thermo‐mechanical modeling

“…The models presented above are incomplete in that they do not incorporate the surface processes, such as erosion and sedimentation. There have been a number of investigations of the coupling and feedback between model tectonics and erosion for orogens [e.g., Beaumont et al, 1994;Avouac and Burov, 1996;Garcia-Castellanos and Jimenez-Munt, 2015;Willett, 1999;Whipple, 2009;Jamieson and Beaumont, 2013;Thieulot et al, 2014;Ueda et al, 2015]. The responses of orogenic wedge systems to climate-driven erosion generally include a decrease in the width of the orogenic belt, a short-term increase in sediment yield, a persistent increase in the rate of rock uplift/exhumation, and a reduction in the subsidence rate of adjacent foreland basins [Whipple, 2009].…”

Stratigraphic response to spatiotemporally varying tectonic forcing in rifted continental basin: Insight from a coupled tectonic‐stratigraphic numerical model

“…Coupled models can be categorized into either "fully coupled models" or "one-way coupled models." Several works have used coupled approaches to study the evolution of tectonic and surface processes in rift settings (Cowie et al, 2006;Geurts et al, 2018) or orogenic settings (Thieulot, Steer, & Huismans, 2014). Although tectonic models solve for complex nonlinear thermomechanics in fully coupled models, surfaceprocess modelling remains rather simple (e.g., slope-dependent diffusion in Olive, Behn, & Malatesta, 2014).…”

“…A set of Python scripts is developed to extract the vertical displacement field for every time step of the tectonic model, which is then applied to the surface-process model as a boundary condition. Our tectonic model is similar to other thermomechanical models in principle (such as the models from Thieulot et al, 2014, or Olive et al, 2014. The main difference in our approach involves the use of a stratigraphic forward model that solves the momentum and transport equations for sediments rather than using a simplified diffusion model to represent flow and sediment transport.…”

Geomorphological–thermo-mechanical modeling: Application to orogenic wedge dynamics

“…This takes place along a multitude of dynamically developing structures that migrate and might steepen towards the backstop. Thrust fault angles, as investigated by other fully coupled 3D studies (Braun and Yamato, 2010;Thieulot et al, 2014) can therefore not be compared directly. In absence of a central structure inherent to the study design, the FTB models, aided by higher resolution, show more variegated feedback between tectonics and surface processes, as surface processes can freely affect the generation and location of structures.…”