Cosmogenic exposure dating

), AE(Climate Change Research Centre, University of New South Wales, Australia), AF(Climate Change Research Centre, University of New South Wales, Australia), AG(Scottish Universities Environmental Research Centre (SUERC), East Kilbride, United Kingdom), AH(Geological Institute, ETH Zürich, Switzerland), AI(Institute of Geological Sciences, University of Bern, Switzerland), AJ(ETH Zürich, Institute of Geochemistry and Petrology, Switzerland) Cosmogenic nuclides are routinely used to investigate deglaciation histories by exposure dating of rock surfaces after glacier retreat.

We compare independent assessments of terrestrial cosmogenic nuclide (TCN) surface exposure ages for glacial deposits that we have determined to those obtained by others at the two sites.

While there is a slew of other dating techniques to choose from, cosmogenic nuclide exposure dating is useful for relatively young (~100 to 10 million years old) samples.

If we are particularly interested in the timing of the uncovering of a surface—say, bedrock that had been covered by ice, or sediments that had been revealed by the incision of a stream—we can employ cosmogenic nuclide surface exposure dating to study that uncovering process.

Because the isotopes we're using have a short half-life, it follows that if a rock has been buried for a few million years the quantities of these isotopes will be negligible.

But when the rock becomes exposed on the surface, and so exposed to cosmic rays, these cosmogenic isotopes will begin to accumulate in the rock.