224 From the Cosmos and Back: Quantifying Processes and Rates of Landscape Change (Posters)

This session explores how methods such as cosmogenic nuclides, apatite (U-Th)/He thermochronometry, U-series geochemistry, luminescence, and chemical mass balances quantify relationships between climate, tectonics, and erosion.

Tuesday, 21 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Transient river processes modulate landscape response to rock uplift in the Colombian Andes

Paper number: 224-2
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The spatial distribution of erosion in mountain landscapes is often interpreted as a response to tectonic forcing, but baselevel dynamics from fluvial processes can exert an important role in a landscapes response to tectonics. We present 10 new 10Be-derived catchment-averaged erosion rates from transverse rivers draining the Garzon Massif in the Eastern Cordillera of Colombia, ranging from 0.05 - 0.5 mm/yr. These erosion rates decrease from north to south and correspond to variations in channel steepness, relief, and slope. Climate and lithology vary slightly across catchments but do not explain the observed erosion gradient.

Erosion rates systematically decrease upstream of two major knickzones along the Magdalena-Sauza River, a longitudinal system that flows parallel to the Garzon Massif within a hinterland basin. We interpret this pattern as a response to baselevel segmentation imposed by the knickzones, which act as barriers to baselevel fall and influence how tributaries respond to rock uplift. Tectonics contribute to spatial erosion patterns, as localized uplift along the Potrillos Thrust likely enhances erosion in transverse drainages downstream of the lower knickzone. Similarly, strike-slip deformation along the Algeciras Fault created a series of pull-apart basins in the upper Magdalena-Sauza system, which are now being incised by the uppermost knickzone. Despite tectonic influences, the transient knickzones along the Magdalena system act as the limiting baselevel control for these transverse rivers. Analyses of the position and morphology of the Magdalena knickzones suggest they are transient features that we interpret to be formed by a combination of drainage capture and regional rock uplift from steepening of the Nazca slab.

In hinterland settings like the one studied here, geomorphic response to uplift is highly sensitive to localized baselevel controls such as local faulting, structural segmentation, sediment trapping, and drainage reorganization. In contrast, tributaries on the eastern flank of the Garzon Massif that drain into the foreland basin exhibit erosion rates more closely tied to regional rock uplift patterns inferred from faulting and thermochronology. These results underscore the importance of drainage configuration and baselevel evolution when interpreting erosional patterns across active orogens.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412994

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.