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| Titel |
Monsoonal vs. glacial control on erosion and sediment storage in the Himalayan rain shadow, Zanskar River, northwest India |
| VerfasserIn |
Tara Jonell, Peter Clift, Andrew Carter, Philipp Böning, Hella Wittmann |
| 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 |
250128242
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| Publikation (Nr.) |
 EGU/EGU2016-8213.pdf |
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| Zusammenfassung |
| Summer monsoon precipitation strongly controls erosion and sediment storage in the frontal
Himalaya but the relationship between monsoonal variability and erosion is less
well-constrained beyond the High Himalayan topographic divide in the rain shadow. Here we
establish a Quaternary erosional history for a rain shadow tributary of the upper Indus River
system, the Zanskar River, by applying several sediment provenance techniques to modern
and dated terrace river sediments. We evaluate if there are temporal links between sediment
storage and moisture supply to the rain shadow and if regions like the Zanskar
River basin play a significant role in controlling total sediment flux to the Indus
River.
We compile bulk sediment petrography and Sr and Nd isotope geochemistry, detrital
U-Pb zircon and apatite fission track dating with in-situ 10Be cosmogenic radionuclide
techniques to identify patterns of erosion and sediment production across Zanskar. Bulk
petrography, Sr and Nd isotope geochemistry, and U-Pb detrital zircon spectra of modern and
older terrace sediments indicate high rates of erosion along the Greater Himalaya in the
Zanskar River basin. We find that the wettest and most glaciated subcatchment dominates the
bulk sediment provenance signal, with only moderate input from other tributaries, and that
other basin parameters cannot explain our observations. Catchment-averaged in-situ 10Be
cosmogenic nuclide concentrations of modern sediments indicate erosion rates up to
∼1.2 mm y−1 but show strong dilution attributed to glacial sediment recycling
into the modern river, suggesting rates nearer 0.4–0.6 mm•y−1. These rates are
consistent with longer-term rates of incision (0.3–0.7 mm•y−1) calculated from
detrital apatite fission track ages, and incision rates inferred from Late Glacial and
Holocene terraces near the Zanskar-Indus confluence. Our findings suggest that
sediment production in glaciated Himalayan rain shadow environments like Zanskar is
largely controlled by internal glacial fluctuations coupled with periodic dissection
and reworking of terrace material during strong monsoonal precipitation phases. |
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