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| Titel |
U-Th and 10Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia |
| VerfasserIn |
Antoine Cogez, Frederic Herman, Eric Pelt, Kevin Norton, Christopher Darvill, Marcus Christl, Gilles Morvan, Thierry Reuschlé, François Chabaux |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135053
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| Publikation (Nr.) |
 EGU/EGU2016-15850.pdf |
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| Zusammenfassung |
| The sedimentary cycle includes the formation by erosion of rocks, transport and deposition.
While erosion and deposition can be documented, the history of sediments between the time
it is extracted from the rocks and ultimately deposited into basins remains a major challenge.
However, the mechanism of transfer and alteration of the sediments during transport plays a
key role in the evolution of basins, feedbacks between erosion and climate, and
glacial-interglacial variability of sediment transport and weathering. This is particularly
true in proglacial settings because large overdeepenings, in particular, are potential
sediment traps for which the efficiency at evacuating those sediments is largely
unknown.
The Lago Buenos Aires moraines in Patagonia are particularly interesting because they
are imbricated from the older in the outer part to the younger in the inner part of the system.
We sampled fine grained sediments from these moraines and measured U-Th isotopes in the
4-50 μm silicate fraction. Deposition ages were refined using 10Be exposure ages. We show
first that the comminution ages model can be improved by measuring also Th isotopes, from
which weathering rates can be deduced. Moreover we show from our data that there is a time
lag of 300 kyr on average between erosion and deposition in the moraine. This could be
attributed to the long residence time of sediments in the lake overdeepening. This conclusion
raises perspectives about the transport times and dynamic of the sediments during a whole
sedimentary cycle, and the subsequent effect on weathering. This conclusion could
also contradict some assumptions commonly made for our erosion rates/sediment
fluxes reconstructions based on river sediments analysis, in recently deglaciated
catchments. |
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