Dynamic interactions between erosion, deposition, and three-dimensional deformation in compressional fold belt settings

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Abstract

[1] This study investigates whether the three-dimensionality of erosion and deposition can influence three-dimensional folding, even when compression is purely convergent. This problem is studied by employing a three-dimensional mathematical model incorporating dynamic thin-plate deformation coupled with fluvial and hillslope sediment transport. The approach taken is to impose several fundamentally different sediment routing patterns (by changing the initial regional topographic slope, β, and the ratio of the characteristic timescales for deformation to fluvial surface processes, R) and to investigate how deformation responds. Numerical results indicate that when β and/or R are small (i.e., initial topography is regionally flat and/or rates of surface processes are slow compared to rate of imposed deformation), folding is two-dimensional and unaffected by surface processes since loads created by surface processes are imposed after deformation. This situation favors development of small-scale drainage networks transporting sediment from anticlines to adjacent basins. When β and/or R are relatively large, the development of a large-scale transverse drainage network, which can be maintained during folding, is able to strongly amplify and localize folding. This leads to interesting features where the largest transverse rivers coincide with the greatest structural and topographic amplitude of doubly plunging folds, which is caused by erosion-enhanced deformation. For intermediate parameter values, folding and surface processes interact in a complex manner, giving rise to three-dimensional en echelon structures that migrate in a transient manner. This study demonstrates that under some circumstances, one can anticipate major two-way interaction between surface processes and three-dimensional deformation.

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