Cosmogenic dating methods
However, most of them are feasible and should be tried.
The general concept of cosmogenic-nuclide burial-dating is that one has a pair of cosmogenic nuclides that are produced at a fixed ratio in some rock or mineral target, but have different decay constants.
Firstly I had to crush the samples in the workshop to shards, and then grind them down on a disc miller.
This was very noisy and dusty, and fairly hard work, but good fun.
Theoretically, exposures of surfaces from between a few thousand to about 10 million years old can be dated by the measurement of the Be-10 and Al-26 isotopes.
| 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.
It was discovered about a decade ago that cosmic ray interaction with silica and oxygen in quartz produced measurable amounts of the isotopes Beryllium-10 and Aluminium-26.
Researchers suggested that the accumulation of these isotopes within a rock surface could be used to establish how long that surface was exposed to the atmosphere.
As 10-Beryllium and 26-Aluminium preferentially build up in quartz, the aim of the first week was to crush down the samples and extract as pure quartz as we could.
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.
Cosmic rays, originating from outer space, bring rare cosmogenic nuclide isotopes (I am using Aluminium) to the Earth’s surface, where they build up in exposed rock surfaces at known rates.
The total concentration of these isotopes in a rock surface therefore represents the length of time that the surface has been exposed to the atmosphere.