IMPLICATIONS OF YOUNGER DRYAS GLACIAL FLUCTUATIONS IN THE WESTERN U.S., NEW ZEALAND, AND EUROPE

With the recent documentation of Younger Dryas moraines of the Cordilleran Ice Sheet (CIS), the northern Cascade Range, the Wind River Mts. and in various other parts of the world, and ice core and sea surface temperature records, the YD glacier readvance is now generally conceded to have occurred globally. However, a closer look at the YD moraines in widely separated parts of the world suggests a double, rather single oscillation of YD glaciers. In the western US, well-dated, double, YD moraines were built by the CIS in the Fraser Lowland (Sumas III (10,980-10,250 14C yrs B.P.) and Sumas IV (~10,250-10,000 14C yrs B.P.). Alpine glaciers built double YD moraines at Titcomb Basin in the Wind River Range, WY (mean of 10Be ages on inner moraine 11,000) and at Temple Lake. This YD double moraine pattern is also found in New Zealand at Arthur’s Pass (mean 10Be age of distal moraine = 11,800, proximal moraine = 11,410 10Be yrs) and at Birch Hill (left lateral avg. 12,100 10Be yrs; right lateral avg. 11,000 10Be yrs) (Ivy-Ochs, et al.,1999). The age of YD moraines at Prospect Hill, NZ is 12,700 10Be yrs. A similar pattern occurs at Julier Pass, Switzerland where the mean 10Be age of the outer YD moraine is 11,750 10Be yrs and the inner moraine 10,470 10Be yrs (Ivy-Ochs, et al.,1999). The double nature of these readvances in widely separated areas in both hemispheres suggests a common climatic cause.