|
Titel |
Quantifying ages of river terraces and basin wide denudation rates in Pamir |
VerfasserIn |
Vasila A. Sulaymonova, Margret C. Fuchs, Richard Gloaguen, Silke Merchel, Georg Rugel |
Konferenz |
EGU General Assembly 2014
|
Medientyp |
Artikel
|
Sprache |
Englisch
|
Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 16 (2014) |
Datensatznummer |
250100257
|
Publikation (Nr.) |
EGU/EGU2014-16155.pdf |
|
|
|
Zusammenfassung |
The Pamir is located at the western edge of the Indian indenter and results from the
India-Asia collision. The Pamir also lies at the transition between zones dominated either by
the Westerlies or the Indian Summer Monsoon. The ongoing tectonic deformation together
with the climatic gradients from the two prevailing atmospheric circulation systems provide a
natural laboratory to study surface processes and their rates. To determine and quantify the
interaction between tectonics and the drainage system in the Tajik Pamir we use cosmogenic
nuclide based techniques.
We measured 10Be and 26Al concentrations of modern fluvial sediments sampled
from drainage system of Pamirs. Depth profiles enable to determine exposure ages
of fluvial terraces, while the modern river sediments reveal basin-wide erosion
rates.
However, accurate measurement results depend on the quality of the sample preparation.
The samples from Pamir contain a high amount of various feldspars that are very difficult to
separate from quartz using standard procedures such as magnetic or density separation.
Unclean samples cause uncertainties in chemical procedures, especially in the case of
combined 10Be and 26Al analysis. We developed a feldspar flotation in addition
to our sample preparation procedure that allowed an almost complete separation
of the quartz, up to 95%. Several depth profiles were analyzed to determine the
exposure age of fluvial terraces. The first results of one terrace along the southern
Panj River east of Langar, and one along the Shakhdara River are promising. The
AMS results demonstrated that the depth profiles are consistent, with 10Be and 26Al
concentrations decreasing with depth. The results of both fluvial terraces show similar
denudation rates 0.5mm/yr., while exposure age analysis yields 3.5 ka for the Langar and
19 ka Shakhdara terrace. Further analyses are ongoing. These ages are validated
by OSL dates at or nearby the same sites. 10Be denudation rates on modern river
samples refine the picture produced by one of us (see Fuchs et al., same session). |
|
|
|
|
|