We will continue to refine the production rate of cosmogenic 3He and 21Ne by collecting additional samples of well-dated lava flows, and we will extend the production rate determination back in time by analyzing K-rich lava flows that can be dated using the laser fusion 39Ar/40Ar technique. We will analyze these recent flows for 3He and 21Ne to establish the production rate beyond 14C chronology. We will also measure 21Ne production rates in quartz and feldspar from Holocene and late Pleistocene flows. In addition we will measure the 21Ne contents of co-existing minerals to establish the compositional dependency of 21Ne production. In addition , we will begin a concentrated effort on determining the mountain deglaciation at the end of the Wisconsin of two regions: the western United States and Canada, and the southern Andes. We will concentrated on volcanic terrains because 3He and 21Ne is quantitatively retained in volcanic pyroxene and olivine; plutonic terrains will be analyzed after we establish the 21Ne production rate in quartz and can separate it from nucleogenic 21Ne production in old (>20 Ma) plutonic rocks. Western North America and the southern Andes will be studied because it is in those two regions that we have established the production rate of 3He and 21Ne (North America), and will extend it back in time (South America). Such constrasting studies will help to establish the Northern and Southern Hemisphere ice sheets were retreating at the same time or not and if the younger Dryas is to be found in western North and South America.
