Watershed-averaged denudation rates from cosmogenic 36Cl in detrital magnetite

• Published in: Earth and planetary science letters Vol. 527; p. 115761
• Main Authors: Moore, Angus K., Granger, Darryl E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2019
• Subjects: chemical weathering; Cl-36; cosmogenic nuclide inter-comparison; detrital minerals; magnetite; watershed denudation rates; magnetite; chemical weathering; detrital minerals; watershed denudation rates; cosmogenic nuclide inter-comparison; Cl-36
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2019.115761

•Cosmogenic 36Cl in magnetite can be used to determine watershed denudation rates.•Magnetite and quartz are similarly resistant to chemical weathering.•Magnetite is likely suitable for determining denudation rates in landscapes without quartz. Quartz is widely used as a target mineral for determining watershed-averaged denudation rates because it is resistant to chemical weathering, geologically widespread, and has a well-constrained 10Be production rate. However, quartz is not available in many landscapes developed on mafic to intermediate igneous rocks. This creates a need to develop new target minerals that are applicable in these environments. Magnetite is a common accessory mineral in many rock types without quartz and, like quartz, is resistant to chemical weathering. Here we evaluate magnetite's suitability as a target mineral by comparing denudation rates inferred from 36Cl in magnetite to 10Be in quartz at 12 watersheds in the Sierra Nevada region of California. We find that magnetite and quartz produce denudation rates that are in broad agreement, validating the use of magnetite. The reproducibility between the two minerals is comparable to the reproducibility of measurements of 10Be from repeat samples of quartz from a single catchment. This level of variance is likely attributable to the stochastic nature of erosion and sediment supply in small, mountainous watersheds.