Cosmogenic dating techniques
In the case of an extrusive volcanic rock, buildup of cosmogenic nuclides begins when the rock is erupted, so measurement of the ratio of a cosmogenic isotope to a non-cosmogenic isotope can provide an estimate of eruption age (Phillips et al., 1986).
The chlorine-36 method (Phillips et al., 1986) is based on the fact that 36-Cl is dominantly produced by cosmogenic reactions near the earth's surface, primarily in the upper 1 m.
| 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.
Cosmogenic nuclide dating uses the interactions between cosmic rays and nuclides in glacially transported boulders or glacially eroded bedrock to provide age estimates for rock at the Earth’s surface.
of an exposed rock, as compared to a very small amount of production in the deeper subsurface.
Chlorine-36 is produced in rocks at the earth's surface almost entirely by cosmic-ray-induced reactions. PHILLIPS, 1994, 36-Cl surface exposure determinations of eruption ages for quaternary lava flows of the Zuni-Bandera volcanic field: New Mexico Geology, v.
Cartoon illustrating cosmogenic nuclide exposure ages. A glacier transports an erratic boulder, and then recedes, exposing it to cosmic rays.
Spallation reactions occur in minerals in the rocks upon bombardment by cosmic rays.
Cosmic rays are attenuated by interaction with the earth's magnetosphere and atmosphere, so the production of 36-Cl is dependent on the latitude and elevation at which the sample was collected.
Dating sediment burial over million-year time scales is crucial in many areas of the Earth sciences and archeology, but is often difficult using traditional techniques.
Sediment burial can be dated by the radioactive decay of cosmogenic nuclides, provided that the sediment was exposed to cosmic rays prior to burial.
These properties have allowed us to create an environment that directly supports the tasks that geoscientists perform as they work on developing new algorithms for cosmogenic dating, such as running calibrations, defining new experiments, and evaluating the impacts of scaling factors on the calculated ages of samples.
Our goal is to provide geoscientists using cosmogenic dating methods with a flexible and powerful software infrastructure upon which to base their future research efforts.