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This suggests that little if any inherited nuclides are present in the sampled boulders.
West of the Last Glacial Maximum (LGM) ice margin in Denmark ages reflect exposure from the Middle Weichselian.
The Bornholm dates agree with the independent age model, however, in the data set for eastern Denmark only less than half the surface exposure ages lie within the expected age envelope.
This apparent mismatch is most likely due to post-glaciation shielding and delayed surface stabilisation compared to the timing of ice-margin retreat.
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.
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.
It is an excellent way of directly dating glaciated regions.
The remaining 42 samples indicate that glacial advances or still-stands of the ice margin occurred at 22.7±0.9, 21.4±1.9, 19.9±1.1, 17.0±0.8, 15.8±0.6, and 14.4±0.9 ka (weighted mean ages ±2, analytical, erosion rate, and attenuation length uncertainties).
This chronology of an outlet of the Patagonian Ice Cap is comparable to many records in the Northern Hemisphere despite a maximum in local summer insolation during this period.
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.