Surface Exposure Geochronology Using Cosmogenic Nuclides: Applications in Antarctic Glacial Geology
2006
Brook, Edward J.
Cosmogenic 3He, 26 Al, and 10Be were measured in Antarctic glacial deposits in the McMurdo Sound-Dry Valleys region to constrain surface exposure ages. Moraines deposited by the Taylor glacier, an outlet glacier of the East Antarctic Ice Sheet, have exposure ages from approx. 120 kyr to 2myr. 10Be and 3He ages of 122 +/- 29 and 134+ / -54 kyr, respectively, for the Taylor II moraine are consistent with deposition during isotope stage 5e (approx. 120 kyr) . Mean 10Be exposure ages for older moraines in the valley of 362 + or - 26 kyr (Taylor III), 1.1 + or 1 0.1 myr (Taylor IVa) and 1.9 + or - 0.1 myr (Taylor IVb) suggest that major ice sheet advances during the last 2 myr were similar in extent to changes during the last glacial-interglacial cycle. Exposure ages for the 'late Wisconsin' Ross Sea Drift, deposited on the coast of McMurdo Sound by the Ross Sea Ice Sheet, range from 8-106 kyr, suggesting that this deposit does not, as previously thought, represent a single ice advance in response to lowered sea level at the last glacial maximum. The data suggest instead that the Ross Sea Ice Sheet may have grounded and advanced on the coast several times during the last glacial period.
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