Patterns of erosion in the Western Alps and quantification of sediment reworking in the associated Po River foreland basin

• Applicant: Dr. Hella Wittmann-Oelze
• Subject Area: Palaeontology
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258542216

Tectonically active mountain belts generate sediment that is, on its journey to the sea, intermittently stored in foreland basins, where it undergoes episodes of temporary storage and reworking. This reworking results in buffering of the eroded sediment fluxes that is caused by diffusive sediment transport and channel-floodplain interaction, causing a missing link in the source-sink connection. As a result, forces like climate cycling 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 rapidly eroding Western and Central European Alps, as well as the Northern Apennines, and the low-relief Po floodplain storing vast amounts of post-orogenic detritus. Until now, widespread recycling of Alpine detritus in the Apenninic accretionary wedge and low apatite and zircon fertility in the Apennines compared to the Alps limited the application of e.g. heavy mineral suites for source rock discrimination and sediment transport. Here, we propose to use a unique combination of mineral fertility analysis and triple in situ-produced cosmogenic nuclides to resolve this challenge. We will first characterize the source areas for their erosion signal using cosmogenic 10Be, then will analyze their downstream changes in relative sediment contributions in the Po plain by using 26Al/10Be ratios in comparison to then known cosmogenic and petrographic source-area fingerprints, and finally, we will determine stable 21Ne concentrations that will allow to assess the residence time of sediment in the Po foreland basin. This approach will lead to a better understanding of reworking of sedimentary deposits and time scales of sediment storage potentially buffering and thus modifying the source area´s erosional signal. Outcomes of this proposal are expected to increase the awareness for the fact that 1) detrital sediments are not transported instantaneously to the sea after their erosion in the source area, 2) that the geochemical fingerprint of such sediments might be integrative over an unknown transfer time, and 3) finally that the sedimentary archive may not necessarily preserve the direct products of erosion episodes but that these may have been modified during floodplain transfer.

• DFG Programme: Research Grants
• International Connection: Italy
• Participating Person: Dr. Marco Malusà