Beryllium 10 cosmogenic dating

SED is now an established tool for geomorphology and landscape change studies.

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Cosmogenic isotopes are created when elements in the atmosphere or earth are bombarded by high energy particles (-mesons and protons, collectively known as cosmic rays) that penetrate into the atmosphere from outer space.

Some cosmic ray particles reach the surface of the earth and contribute to the natural background radiation environment.

Our samples are now pre-treated at the University of Canterbury.

Ne chronologies from 21 erratic boulders on three moraine sequences in Nyalam county, monsoonal Himalayas, southern margin of the Tibetan Plateau.

The surface exposure ages provide evidence for at least two distinct glacial advances during the late stage of the last glacial cycle and for one or more significantly older glaciations.

The distribution of cosmogenic ages from the three ridges of the old moraine sequence is inconsistent with their stratigraphic order.

If rocks are undisturbed for millennia, differences in the cosmogenic isotope content of the upper and lower surfaces accumulate.

These differences can be translated into a measure of time since the rocks were either first exposed to sunlight, or covered over and isolated from the cosmic ray flux.

Because exposure periods of the erratics prior to deposition on the moraine surface is shown to be small, the chronology–stratigraphy mismatch suggests that the cosmogenic ages do not date moraine deposition but most likely significant moraine ridge denudation and related boulder exhumation after initial deposition of the moraines during the penultimate glacial cycle or earlier.

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