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| Titel |
Neogene basin infilling from cosmogenic nuclides (10Be and 21Ne) in Atacama, Chile |
| VerfasserIn |
Caroline Sanchez, Vincent Regard, Sébastien Carretier, Rodrigo Riquelme, Pierre-Henri Blard, Eduardo Campos, Stéphanie Brichau, Marteen Lupker, Gérard Herail |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144484
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| Publikation (Nr.) |
 EGU/EGU2017-8315.pdf |
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| Zusammenfassung |
| In the hyperarid Atacama Desert, northern Chile, Neogene sediments host copper rich layers
(exotic supergene mineralization). Current mines are excavated into relatively thin
(<200-300 m) Neogene basins whose infilling chronology is poorly constrained. We took
advantage of one of these mining pits, and sampled for 10Be and 21Ne cosmogenic
nuclide dosing. These cosmogenic nuclides help constraining the infilling chronology.
Indeed, basin sediments were deposited with a cosmogenic nuclide content acquired
on hillslopes. Then within the basin, cosmogenic nuclide concentrations evolved
through the competing production (quickly decreasing with depth) and disintegration
(not for 21Ne). Sampling depths are at ∼100 m and at ∼50 m below the desert
surface.
First, 21Ne gives lower boundaries for upstream erosion rates or local sedimentation rate.
These bounds are between 2 and 10 m/Ma, which is quite important for the area. The ratio
between the two cosmogenic nuclides indicate a maximum burial age of 12 Ma
(minimal erosion rate of 15 m/Ma) and is surprisingly similar from bottom to top,
indicating a probable rapid infilling. We finally processed a Monte-Carlo inversion.
This inversion helps taking into account the post-deposition muonic production of
cosmogenic nuclides. Inversion results is dependent on the muonic production scheme.
Interestingly, the similarity in concentrations from bottom to top pleads for quite low
production at depth. Our data finally indicates a quick infilling between 12.5 and 10
Ma BP accounting for ∼100 m of deposition (minimum sedimentation rate of 40
m/Ma). |
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