Cosmogenic isotope surface exposure dating

This diagram, showing thinning of an ice sheet from the Last Glacial Maximum (LGM) to present day, helps to visualise how this works: When an ice sheet thins, rocks transported within it (erratics – shown here as red circles) are left perched on mountainsides – known as ‘nunataks’ when surrounded by ice – at a range of heights above the modern ice sheet surface.Thus nunataks act as a ‘dipstick’ for the former height of the ice sheet surface.This work was done in collaboration with Julie Libarkin at Ohio University.Work continues with Doug Burbank at UCSB and Caltech graduate student Willy Amidon.Attribution: You must attribute the work in the manner specified by the author or licensor (but no in any way that suggests that they endorse you or your use of the work).

No longer should it be considered a major player in postglacial sea-level rise.This technique involves measuring the abundance of isotopes that are produced within rock surfaces when they are exposed to cosmic radiation.Ice cover blocks the penetration of cosmic radiation, halting production of such isotopes; their abundance in a rock therefore gives a measure of the time since ice retreated: the ‘exposure age’.Results of a large Al is the formation of sufficient negative Al ions during sputtering, which is only about 25% efficient (Middleton and Klein, 1987).The metal species must be used rather than the oxide because the latter suffers a severe interference from is in the measurement of rock exposure ages. The upper curve shows the effect of increasing exposure age, for the case where the erosion rate is zero.No Derivative works ‒ You may not alter, transform, or build upon this work.

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