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Isochron‐burial dating of glaciofluvial deposits: First results from the Swiss Alps
Author(s) -
Akçar Naki,
IvyOchs Susan,
Alfimov Vasily,
Schlunegger Fritz,
Claude Anne,
Reber Regina,
Christl Marcus,
Vockenhuber Christof,
Dehnert Andreas,
Rahn Meinert,
Schlüchter Christian
Publication year - 2017
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.4201
Subject(s) - isochron , geology , isochron dating , geochemistry , bedrock , glacial period , clastic rock , cosmogenic nuclide , lithology , geomorphology , mineralogy , paleontology , sedimentary rock , physics , cosmic ray , astrophysics
In this study, we use isochron‐burial dating to date the Swiss Deckenschotter, the oldest Quaternary deposits of the northern Alpine Foreland. Concentrations of cosmogenic 10 Be and 26 Al in individual clasts from a single stratigraphic horizon can be used to calculate an isochron‐burial age based on an assumed initial ratio and the measured 26 Al/ 10 Be ratio. We suggest that, owing to deep and repeated glacial erosion, the initial isochron ratio of glacial landscapes at the time of burial varies between 6.75 and 8.4. Analysis of 22 clasts of different lithology, shape, and size from one 0.5 m thick gravel bed at Siglistorf (Canton Aargau) indicates low nuclide concentrations: <20 000 10 Be atoms/g and <150 000 26 Al atoms/g. Using an 26 Al/ 10 Be ratio of 7.6 (arithmetical mean of 6.75 and 8.4), we calculate a mean isochron‐burial age of 1.5 ± 0.2 Ma. This age points to an average bedrock incision rate between 0.13 and 0.17 mm/a. Age data from the Irchel, Stadlerberg, and Siglistorf sites show that the Higher Swiss Deckenschotter was deposited between 2.5 and 1.3 Ma. Our results indicate that isochron‐burial dating can be successfully applied to glaciofluvial sediments despite very low cosmogenic nuclide concentrations. Copyright © 2017 John Wiley & Sons, Ltd.