Interplay between lithospheric flexure and river transport in foreland basins

Abstract

Foreland basins form by lithospheric flexure under orogenic loading and are filled by surface transport of sediment. This work readdresses the interplay between these processes by integrating in a 3D numerical model: the mechanisms of thrust stacking, elastic flexural subsidence and sediment transport along the drainage network. The experiments show that both crustal tectonic deformation and vertical movements related to lithospheric flexure control and organise the basin‐scale drainage pattern, competing with the nonlinear, unpredictable intrinsic nature of river network evolution. Drainage pattern characteristics are predicted that match those observed in many foreland basins, such as the axial drainage, the distal location of the main river within the basin, and the formation of large, long‐lasting lacustrine systems. In areas where the river network is not well developed before the formation of the basin, these lithospheric flexural effects on drainage patterns may be enhanced by the role of the forebulge uplift as drainage divide. Inversely, fluvial transport modifies the flexural vertical movements differently than simpler transport models (e.g. diffusion): Rivers can drive erosion products far from a filled basin, amplifying the erosional rebound of both orogen and basin. The evolution of the sediment budget between orogen and basin is strongly dependent on this coupling between flexure and fluvial transport: Maximum sediment accumulations on the foreland are predicted for a narrow range of lithospheric elastic thickness between 15 and 40 km, coinciding with the Te values most commonly reported for foreland basins.

Neotectonics, flooding patterns and landscape evolution in southern Amazonia

“…The uplift of the forebulge is very small (a few hundred metres over a distance of several hundred kilometres) and an inherited (preflexural) topographic relief can be more important than the forebulge in determining the drainage divide (Garcia-Castellanos and Cloetingh, 2011). Nevertheless, in models of continental and exorheic basins, the effect of the forebulge on the drainage network is generally evident (Garcia-Castellanos, 2002). In an extremely flat landscape, such as that of the LM, an uplift along the forebulge axes which is able to create the Puerto Siles knickpoint would be visible in the subsequent formation of a divergent drainage network.…”

Forward modelling of the Bureba escarpment (Rioja Trough, N-Spain)

“…All equations are solved using the finite difference technique in both space and time [5]. Test models revealed three main categories of parameters, namely (1) elastic thickness, (2) runoff, and (3) erodability.…”

“…Where dq is amount of sediment deposited or eroded along a river segment of length dl, q is actual sediment load, q eq is equilibrium sediment load, l f is the length scale of erosion/deposition, which I call erodability or Er in this work [5]. I use a fourth order differential equation [9] that relates the flexural elastic deflection related to a 2D load distribution.…”

“…The model used in this study was developed by [5] and incorporates planform solutions to the following processes:…”

LitMod3D: An interactive 3‐D software to model the thermal, compositional, density, seismological, and rheological structure of the lithosphere and sublithospheric upper mantle

“…This allows discerning whether low-wavelength misfits between the observed topography and the local isostatic topography compensating the assumed lithospheric structure can be due to a regional isostatic support assuming reasonable Te values. [48] LitMod3D computes flexural isostasy by using the finite difference code TISC (cuba.ija.csic.es/$danielgc/tisc/) [Garcia-Castellanos, 2002], which requires the 2-D load distribution and a representative effective elastic thickness for the lithosphere. The flexural load q(x, y) is given by pressure variations at the compensation level.…”