Terrestrial cosmogenic nuclide dating
Created by the author of the page containing this file. Sampling river sands in the Beas Valley of the Greater Himalaya of Northern India to determine the concentrations of terrestrial cosmogenic nuclides to calculate rates of catchment wide erosion.
Details1500 km north-south with an average elevation of ~5000 m above sea level.
The concentration of TCNs increases with time in an exposed surface. The rate of production for a particular TCN depends on latitude and altitude.
When accurately determined the TCN concentration in a rock or sediment surface provides an estimate of the time that surface has been exposed to cosmic rays.
Continent: Asia Country: Pakistan, India, Nepal and China State/Province: N/A City/Town: N/A UTM coordinates and datum: none Climate Setting: Tropical Tectonic setting: Continental Collision Margin Type: Process Figure 1.
View of strath terrace along the Chandra River in the Lahul Himalaya of Northern India.
Moreover, studies have shown that rates of erosion may vary considerably over the very short timescale of the study due contrasting weather conditions from one year to the next associated with a monsoon climate.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.There are lots of caveats that need to be considered when determining an TCN age, for example, if the surface was shielded from cosmic rays by a cover of sediment or soil until recently.In a simple situation such as bedrock eroded by rivers and left high above the valley side when the river progressively cuts down then the concentrations of TCNs in that surface (a strath terrace) will provide an age of river abandonment (Fig. An erosion river (fluvial) rate can be determined by simply dividing the surface age of the strath terrace by its height above the present river.