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| Titel |
Eocene Tibetan Plateau remnants preserved in the Northwest Himalaya |
| VerfasserIn |
P. A. van der Beek, J. Van Melle, S. Guillot, A. Pecher, P. W. Reiners, S. Nicolescu, M. Latif |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022211
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| Zusammenfassung |
| The northwest Himalaya shows strongly contrasting relief, opposing deeply incised
mountain ranges characterized by extremely rapid exhumation and some of the
highest peaks in the world (i.e., the Karakorum range and Nanga Parbat massif) to
high-elevation, low-relief areas such as the 4000-m high Deosai plateau in northern Pakistan
and the 5000-m high Tso Morari in Indian Ladakh. The origin and evolution of
such plateau regions in the syntaxis of the most active continental collision in the
world remain elusive. Here, we report the first low-temperature thermochronology
(apatite fission-track, apatite and zircon (U-Th)/He) data from the Deosai plateau
and use thermal history modelling to show that it has undergone continuous slow
(≤ 200 m/Myr) denudation and has thus remained tectonically stable for the last
35 Myr at least. The inferred history of constant slow denudation of the plateau
contradicts the hypothesis that widespread low-relief surfaces in the northwest
Himalaya result from efficient, km-scale glacial erosion during Quaternary times; such
erosion would have been recorded as a phase of rapid recent denudation that is not
observed in the data. Slow continuous denudation since Eocene times, i.e. only 15-20
Myr after the onset of India-Asia collision implies that the Deosai plateau surface
developed early in the Himalayan history and limits the phase of orogenic relief growth
in the Ladakh-Kohistan arc to the early Paleogene. Although thermochronology
data do not directly record surface uplift, the simplest explanation for the inferred
constant denudation rates is that the plateau had reached its present-day elevation
already during the Eocene, as a later phase of surface uplift would have triggered an
erosional response that would have been recorded by the thermochronology data.
We use morphological analyses to characterise such plateaux and identify them at
the scale of the entire northwest Himalaya and compare our thermochronological
data with scattered published data from the other plateau and low-relief summit
regions in the northwest Himalaya. We show that the plateau regions share common
morphologic characteristics and denudation histories, which are comparable to those
of the western Tibetan plateau. These results imply that they may be preserved
remnants of an Eocene south-western Tibetan plateau that was more widespread
than today and that was subsequently dissected by rivers following major faults. |
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