Terrestrial cosmogenic nuclide dating

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Concentrations of TCNs are lowest in transported sediment in catchments that have the highest erosion rates (see Portenga and Bierman, 2011 for more details).

Sampling stream sands and measuring the TCN concentrations can be directly used to determine basin wide erosion rates (Fig. Such studies are showing strong contrasts between catchments in different climatic and tectonic zones in the Himalaya and Tibet (see Seong et al., 2009b and Dortch et al., 2012 as examples).

Rivers, glaciers, mass movement processes and the wind transport eroded sediment through mountain catchments.

TCN concentrations in sediments can also be used to determine rates of erosion averaged across a mountain catchment.

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Erosion rates based on strath terraces younger than about 35,000 years likely reflect sporadic and accelerated erosion.

These are giving erosion rates that vary from a few tens of meters to hundreds of meters per million years.

The differences in rates of erosion likely reflect different climate and tectonic settings, but it is usually difficult to resolve which of the two sets of processes dominate.

Long term rates of uplift have been broadly defined using petrological and structural geological methods, which essentially indicate how quickly rock is brought to the surface and/or exhumed.

Recently, global positioning systems have been used to determine short-term (years-decades) rates of surface displacement.

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