Old Crow tephra (140 ± 10 ka) constrains penultimate Reid glaciation in central Yukon Territory

Old Crow tephra (140 ± 10 ka) is closely associated with deposits from the penultimate Reid glaciation along the Pelly River in central Yukon Territory. The elevation of the tephra above present base level and association with deglacial sediments suggests a close minimum age estimate, confirming a MIS 6 age for the Reid glaciation. This is in contrast to a MIS 4 age for the penultimate Gladstone glaciation in southwest Yukon. This study demonstrates that the assumed synchrony of the penultimate advance of the Cordilleran Ice Sheet has little support, and regional controls on the mass balance of source regions of the ice sheet are more important than previously considered.