Patterns of erosion in the Western Alps and quantification of sediment reworking in the associated Po River foreland basin
Final Report Abstract
Tectonically active mountain belts generate sediment that undergoes, on its journey to the sea, episodes of temporary storage and reworking. This reworking results in a potential change of the eroded sediment fluxes, causing a missing link in the source-sink connection. As a result, forces like climate change controlling sediment export cannot be linked directly to preserved sedimentary successions. The Po drainage basin is an excellent test site to evaluate the timescales and magnitudes of sediment transport and mixing patterns, as it integrates over the well-studied European Alps, as well as the Northern Apennines, and the low-relief Po floodplain storing vast amounts of sediment. Until now, the low abundance of apatite and zircon minerals in the Apennines compared to the Alps limited the application of e.g. heavy mineral suites for source rock discrimination and sediment transport. In this study, we used a unique combination of mineral fertility analysis and in situ-produced cosmogenic nuclides to resolve this challenge. We characterized the source areas for their erosion signal using cosmogenic 10Be and then analyzed their downstream changes in relative sediment contributions in the Po plain by using 26Al/10Be ratios that showed that storage times of sediment in the Po foreland basin did not exceed the half life of 10Be (1.4 Ma). Further, we found that the Apatite mineral record at the Po delta may be dominated by high-fertility source rocks exposed within the drainage; the detrital thermochronology record may thus reflect processes affecting only relatively small parts of the orogenic system, and may underrepresent major orogenic segments even if these are characterized by fast erosion but low mineral abundance.
Publications
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(2017) Trace-element and Nd-isotope systematics in detrital apatite of the Po river catchment: Implications for provenance discrimination and the lag-time approach to detrital thermochronology. Lithos 290-291 48–59
Malusà, Marco G.; Wang, Jiangang; Garzanti, Eduardo; Liu, Zhi-Chao; Villa, Igor M.; Wittmann, Hella
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(2016): “The cosmogenic record of mountain erosion transmitted across a foreland basin: source-to-sink analysis of in situ 10Be, 26Al and 21Ne in sediment of the Po river catchment”. Earth and Planetary Science Letters, Vol. 452, p. 258-271
Wittmann, H., Malusà, M., Resentini, A., Garzanti, E., Niedermann, S.
