Cosmogenic surface exposure dating
Several factors can affect cosmogenic nuclide dating: rock type, attenuation of cosmic rays, topographic shielding, post-depositional movement, and burial and cover by snow, vegetation or earth.Geologists must ensure that they choose an appropriate rock.It is particularly useful in Antarctica, because of a number of factors: Cosmogenic nuclide dating is effective over short to long timescales (1,000-10,000,000 years), depending on which isotope you are dating.Different isotopes are used for different lengths of times.Access to society journal content varies across our titles.
When particular isotopes in rock crystals are bombarded by these energetic cosmic rays neutrons, a reaction results.
This is important for glacial geologists, as it means that surfaces that have had repeated glaciations with repeated periods of exposure to cosmic rays can still be dated, as long as they have had sufficient glacial erosion to remove any inherited signal.
Glacial geologists use this phenomenon to date glacial landforms, such as erratics or glacially transported boulders on moraines or glacially eroded bedrock.
Dating glacial landforms helps scientists understand past ice-sheet extent and rates of ice-sheet recession.
The basic principle states that a rock on a moraine originated from underneath the glacier, where it was plucked and then transported subglacially.