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Titel |
Long-term stability of peneplains and landscape evolution in southern Tibet inferred from field data, cosmogenic nuclides, and digital elevation models |
VerfasserIn |
M. Strobl, R. Hetzel, L. Ding, L. Zhang |
Konferenz |
EGU General Assembly 2010
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 12 (2010) |
Datensatznummer |
250033438
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Zusammenfassung |
Peneplains constitute a widespread and well developed geomorphic element on the Tibetan
Plateau, nevertheless little is known about their formation and the subsequent landscape
evolution. In southern Tibet, north of Nam Co (~31Ë 20’N, 90Ë E), a particularly
well-preserved peneplain occurs at an elevation of ~5350Â m in Cretaceous granitoids. The
main planation surface has been incised by small streams that formed additional small
low-relief surfaces at lower elevations. Fluvial incision of the main peneplain has generated a
local relief of up to ~700Â m. The progressive incision has led to hillslope gradients that
increase with decreasing elevation, i.e. from the main peneplain at ~5350 m down to the
current base level at ~4650Â m, as revealed by field observations and the analysis of digital
elevation model.
In order to quantify the landscape evolution of the peneplain region we determined local
and catchment-wide erosion rates from the concentration of in situ-produced cosmogenic
10Be. Local erosion rates on the main peneplain and the low-relief bedrock surfaces at lower
elevation range from 6 to 12 m Ma-1 and indicate that the geomorphic surfaces
are stable over long periods of time. Spatially integrated erosion rates of small
river systems that are incising and eroding headwards into the main peneplain are
only slightly higher and range from 11 to 18 m Ma-1. Even if river incision has
proceeded at a rate that is 2-4 times higher than the catchment-wide erosion rates,
i.e. at 30 to 60 m Ma-1, it would take about 10 to 20 Ma to generate the local
relief of ~700Â m observed today. This demonstrates that the major peneplain is a
very stable geomorphic element with a minimum age of 10 to 20Â Ma and that the
landscape in the region has barely been modified by erosion in the last millions of years. |
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