How can we date rocks? Using cosmogenic nuclides in glacial geology Sampling strategies cosmogenic nuclide dating Difficulties in cosmogenic nuclide dating Calculating an exposure age Further Reading References Comments. Cosmogenic nuclide dating can be used to determine rates of ice-sheet thinning and recession, the ages of moraines, and the age of glacially eroded bedrock surfaces. For glaciation, the most common application of cosmogenic nuclide dating is to date the exposure age of glacially transported rocks. It tells us how long the rocks have been located at the surface, for example, on a moraine. It is an excellent way of directly dating glaciated regions.
Terrestrial cosmogenic nuclide dating
Cosmogenic nuclide - Wikipedia
The Earth is constantly bombarded by galactic cosmic rays, which primarily consist of protons. This secondary cosmic ray shower is rapidly attenuated as it travels down into the atmosphere. Only a very small fraction of the secondary cosmic rays, which mostly consist of neutrons, reach the surface of the Earth. These neutrons then collide with the elements that are found in rocks and soils, such as silicon, oxygen, calcium etc. But some of the spallation products are very rare yet sufficiently long lived to accumulate in measurable quantities in terrestrial rocks. One example is 10 Be, which has a half life of 1. This is orders of magnitude shorter than the age of the Earth.
Take the virtual tour of the Cosmogenic Nuclide Lab. Because we know the rates at which these isotopes are produced, the concentrations of cosmogenic nuclides in rock, soil, sediment, etc. The facilities include 2 HF rated extraction hoods and one laminar flow hood, Parr pressure dissolution oven, as well as analytical balances and centrifuge. The applications of cosmogenic nuclide methods span the Earth Sciences. Absolute dating of glacial moraines and river terraces, for example provide vital constraints on paleo-climate impacts on the landscape.
In the last decades surface exposure dating using cosmogenic nuclides has emerged as a powerful tool in Quaternary geochronology and landscape evolution studies. Cosmogenic nuclides are produced in rocks and sediment due to reactions induced by cosmic rays. Landforms ranging in age from a few hundred years to tens of millions of years can be dated depending on rock or landform weathering rates by measuring nuclide concentrations.