Tectonic and climatic influences on bedrock channels traversing the central Andes, Bolivia

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Syrek, Jonathon Foster
- Affiliation: College of Arts and Sciences, Department of Geological Sciences

Abstract

I combine rock strength variations estimated from field data and topographic analyses of 252 channels across the semiarid southern Bolivian Andes to investigate the role of tectonics on knickpoint formation and bedrock channel steepness patterns. Sixty percent (17 of 29) of knickpoints along 4 trunk rivers are spatially correlated with a rock unit transition. Seventy-seven percent (10 of 13) of identifiable knickpoint morphologies (vertical-step versus slope-break) that correlate with a rock unit change match a recently published theoretical framework. Knickpoints in southern Bolivia are only small-scale, local features. Larger, regional steepness patterns are not simply correlated to rock strength, but instead I argue they are primarily influenced by the fold-thrust belt architecture and associated active rock uplift patterns dictated by large-scale basement deformation. In contrast, rivers in northern Bolivia possess more systematic downstream decreases in channel steepness and high profile concavities that reflect strong influences from enhanced orographic precipitation.

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