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Cosmogenic exposure dating

Snow-cover history is difficult to constrain, but its effect is thought to be minor for the tall boulders sampled.Despite these complications, the CE ages provide important new information regarding the timing of the last and penultimate glaciations in Alaska. PY - 2005/7Y1 - 2005/7N2 - 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.SED is now an established tool for geomorphology and landscape change studies.Surface exposure age dating requires intensive chemistry.Despite these complications, the CE ages provide important new information regarding the timing of the last and penultimate glaciations in Alaska.Three penultimate moraines yielded CE ages that overlap with marine isotope stage (MIS) 4/early MIS 3 (45-65 ka) rather than MIS 6 (ca. Based on a combination of our new CE chronologies and existing 14C ages from six study areas, glaciers retreated from their local late Wisconsin maxima: ca.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.

The particles bounce about in the magnetic field of the remnant anomaly until they gain sufficient energy to escape the system, whereupon they become cosmic rays. It is now known that most cosmic rays are atomic nuclei.

Three penultimate moraines yielded CE ages that overlap with marine isotope stage (MIS) 4/early MIS 3 (45-65 ka) rather than MIS 6 (ca. Based on a combination of our new CE chronologies and existing C ages from six study areas, glaciers retreated from their local late Wisconsin maxima: ca. Boulder exhumation during moraine degradation likely gives rise to the largest uncertainty in constraining the timing of initial moraine stabilization following ice retreat.

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. Isotopic inheritance appears to be most important for moraines deposited close to their cirque headwalls.

24-26 ka, northeastern Brooks Range (NE Alaska); ca. TY - JOURT1 - Cosmogenic exposure dating of late Pleistocene moraine stabilization in Alaska AU - Briner, Jason P. Boulder-surface (bedrock) erosion rate can be roughly constrained and leads to a range in moraine stabilization ages.

21-23 ka, Yukon Tanana Upland (east-interior Alaska); ca. Snow-cover history is difficult to constrain, but its effect is thought to be minor for the tall boulders sampled.

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The first interaction is when the high energy particles collide with nuclei in the upper atmosphere. A spallation reaction is a nuclear reaction where a highly energetic nucleon (usually a secondary cosmic-ray neutron of energy) collides with a target nucleus.

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