Most rocks contain an assemblage of ferrimagnetic particles that record the ambient magnetic field present at the time of the rock's formation. Uncertainty in the acquisition and demagnetization temperatures can limit the utility of pVRM for absolute dating. For the three younger moraines, the average T D yields an age comparable to the cosmogenic age, within uncertainty of pVRM acquisition temperature. Both the maximum and average pVRM demagnetization temperatures ( T D) increase with relative age of the moraines. The moraines are composed primarily of granodiorite boulders, and magnetic remanence is carried dominantly by magnetite. We test this hypothesis at four nested glacial moraines in the Icicle Creek drainage of central Washington, the ages of which were previously determined by cosmogenic surface exposure dating. An established theoretical relationship between the time and temperature of acquisition of VRM and the time and temperature of demagnetization suggests that laboratory demagnetization (unblocking) of VRM can be used to estimate the displacement age of rocks. Viscous remanent magnetization (VRM) may partially overprint original magnetization in rocks displaced by geomorphic events.
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