Continued Use of Cosmogenic 3He and 21 Ne in Dating Geomorphic Surfaces

我们将通过收集更多的确定年代的熔岩流样本，继续完善宇宙成因3He和21Ne的产率，我们将通过分析可以使用激光聚变39Ar/40Ar技术确定年代的富k熔岩流来延长产率测定的时间。我们将分析3He和21Ne最近的流量，以确定超过14C的产量。我们还将测量全新世和晚更新世流中石英和长石的21Ne产率。此外，我们将测量共存矿物的21Ne含量，以建立21Ne生产的成分依赖性。此外，我们将开始集中精力，确定美国西部和加拿大西部以及安第斯山脉南部两个地区威斯康星州末端的山地冰川消融情况。我们将重点研究火山地形，因为3He和21Ne在火山辉石和橄榄石中被定量保留；建立了石英中21Ne的产率，并将其与老（20 Ma）深部岩石的成核21Ne产率区分开，对深部地形进行了分析。我们将研究北美西部和安第斯山脉南部，因为正是在这两个地区，我们已经建立了3He和21Ne的产量（北美），并将在时间上延长（南美）。这种对比研究将有助于确定北半球和南半球冰盖是否在同一时间消退，以及是否在北美和南美西部发现了更年轻的仙女木期。

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.