Al ages from 57 moraine boulders and 2 tors, together with 43 previously published cosmogenic exposure ages from 41 moraine boulders, allow us to critique the use of cosmogenic exposure (CE) dating of moraine boulders in Alaska.Boulder exhumation during moraine degradation likely gives rise to the largest uncertainty in constraining the timing of initial moraine stabilization following ice retreat.Also, the exposure assumptions must be justified through other means, for example by taking into account clear signs of surface erosion and information consistent with (or suggestive of) 100% shielding prior the exposure event to be dated.
Our samples are now pre-treated at the University of Canterbury.
C in our atmosphere, which is used in radiocarbon dating, and in the production of cosmogenic nuclides in rocks at the Earth surface, which we use in cosmogenic nuclide dating[1-3].
Most are hydrogen nuclei, some are helium nuclei, and the rest heavier elements.
The relative abundance changes with cosmic ray energy — the highest energy cosmic rays tend to be heavier nuclei.
24-27 ka, Kokrines Hills (west-interior Alaska); ca. Overall, glacier retreat was concurrent with the peak of the last global glacial maximum, probably in response to limited moisture availability.
24-26 ka, northeastern Brooks Range (NE Alaska); ca. AB - Seventy-three new 10Be/26Al ages from 57 moraine boulders and 2 tors, together with 43 previously published cosmogenic exposure ages from 41 moraine boulders, allow us to critique the use of cosmogenic exposure (CE) dating of moraine boulders in Alaska.
21-23 ka, Yukon Tanana Upland (east-interior Alaska); ca.
Be production rate is carefully calibrated, for example by correcting for partial attenuation and complete shielding effects.
SED is now an established tool for geomorphology and landscape change studies.
Surface exposure age dating requires intensive chemistry.
Although many of the low energy cosmic rays come from our Sun, the origins of the highest energy cosmic rays remains unknown and a topic of much research.