Tectonic and Climatic Controls on the Spatial Distribution of Denudation Rates in Northern Chile (18°S to 23°S) Determined From Cosmogenic Nuclides

• Published in: Journal of geophysical research. Earth surface 2017-10, Vol.122 (10), p.1949-1971
• Main Authors: Starke, J., Ehlers, T. A., Schaller, M.
• Format: Article
• Language: English
• Subjects: Andes; Annual precipitation; Arid regions; Arid zones; Banks (topography); Beryllium 10; Catchment area; Catchment scale; Catchments; Chile; Climate control; Coastal environments; Correlation; cosmogenic nuclides; Denudation; denudation rates; Drainage area; Drainage basins; Environmental conditions; Factor analysis; Mean annual precipitation; Nuclides; Orogeny; Plate tectonics; Precipitation; Sediments; Seismology; Slope; Slopes; Spatial distribution; Spatial variations; Statistical analysis; Stream order; syntaxis; Tectonic processes; Tectonics; Topography; Topography (geology)
• ISSN: 2169-9003; 2169-9011
• DOI: 10.1002/2016JF004153

In the arid region of northern Chile the environmental conditions are favorable for measuring tectonic and climatic influences on catchment denudation rates in the absence of vegetation. Previous studies of denudation rates from cosmogenic 10Be and 26Al concentrations are limited to single drainages. In this study, we examine catchment‐ to orogen‐scale spatial variation in denudation rates between 18 and 23°S in the Coastal and Western Cordilleras of northern Chile. 10Be and 26Al data were obtained from 33 catchments to examine the relative roles of tectonics and climate on catchment‐averaged denudation rates. At broader scales, we examine whether denudation rates and orogen topography reflect the 3‐D plate geometry of the region. Cosmogenic nuclide‐derived denudation rates range from 0.4 ± 0.5 to 20.6 ± 1.5 m/Myr in the Coastal Cordillera and from 1.4 ± 0.7 to 168.0 ± 19.8 m/Myr in the Western Cordillera. The controls on the denudation rates are evaluated using a statistical factor analysis of 10 selected catchment parameters. Denudation rates indicate a strong linear relationship with channel steepness indices but insignificant correlations and covariation with mean annual precipitation rates, drainage area, stream order, mean elevation, mean local relief, mean basin slope, and grain size of the sampled sediments. Moreover, denudation rates are better correlated with tectonic controls at catchment scale than orogen‐scale plate tectonics in the Western and Coastal Cordillera. Key Points Analyzing tectonic and climatic influences on 10Be‐ and 26Al‐derived denudation rates in a syntaxial orogen Significant correlation and covariation of denudation rates and channel steepness indices Catchment‐scale tectonic processes rather than orogen‐scale topographic trends control denudation rates in this arid setting