Base-level and lithologic controls of drainage reorganization in NW Argentina
Abstract
Drainage reorganization is increasingly recognized as a common feature of transient landscapes, particularly in tectonically-active settings. Such landscape transience is often used to examine potential perturbations in tectonics and climate, such as changes in uplift rates or precipitation gradients. Therefore, elucidating patterns and controls of reorganization can provide a new tool in understanding how landscapes respond to changes in boundary conditions. Sierra de las Planchadas, a thin-skinned range in NW Argentina, presents the ideal location in which to study patterns and controls of reorganization. Low out-of-channel erosion rates preserve indicators of drainage reorganization and minimal evidence of glaciations or mass movements suggests that range morphology is solely the result of fluvial erosion patterns. Using geomorphic evidence of reorganization, such as wind gaps, capture elbows, and knickpoints, and the morphometric indicators, χ, ksn, and flow azimuth distributions, we identify three board patterns of drainage reorganization: the westward migration of the main drainage divide, basin growth on the eastern side of the range in response to increasing flank width, and the capture of N-S longitudinal reaches by E-W transverse drainages. We evaluate these reorganization patterns given four potential controls - precipitation gradients, the distribution of resistant lithologies, spatial variations in uplift rates, and base-level differences between the two range-bounding basins. We conclude that both the westward migration of the main drainage divide and subsequent growth of eastern basins are due to base-level differences that resulted from the passive uplift of the western range-bounding basin during mountain building. However, the preservation of longitudinal headwaters is likely linked to the resistance of adjacent lithologies; resistant units, such as granitoids and high-grade metamorphics, impede transverse drainages from eroding through divides and therefore protect longitudinal reaches. We explore the potential response timescales of such reorganization and the implications for using transient drainage patterns as indicators of boundary condition perturbations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP11B..02S
- Keywords:
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- 1815 Erosion;
- HYDROLOGYDE: 1825 Geomorphology: fluvial;
- HYDROLOGYDE: 1826 Geomorphology: hillslope;
- HYDROLOGYDE: 1861 Sedimentation;
- HYDROLOGY