Collaborative Research: Uplift of the Washington Cascades and Climatic Evolution of Eastern Washington

华盛顿瀑布是北美最大的气候雨影之一，西侧部分地区的年平均降水量超过4 m/yr，东侧低于0.15 m/yr。我们正在研究的时间之间的关系，在这个区域的环境中，通过使用低温磷灰石（U-Th）/He thermochronometry在级联结晶岩石本身的组合方法，和稳定同位素变化的自生矿物在粘土和碳酸盐在古土壤中的不同年龄的干燥，东侧的范围。此外，通过结合地理信息系统和他的测年工作，我们正在研究之间的关系创建的瀑布地形起伏和更新世最近的冰川作用的范围内，并评估的作用相对较新的侵蚀力造山带折返。我们的初步工作表明，他的年龄记录比其他放射性系统在瀑布年轻得多的年龄，这表明一个相对较近的（晚中新世最早）时期的发掘，这是一致的古生物学证据从东部华盛顿缺乏一个严重的气候对比，直到这个时候。

MontgomeryReiners00874130087318The Washington Cascades cast one of the largest climatic rain shadows in North America, with mean annual precipitation in some areas on the west side higher than 4 m/yr, and on the east side lower than 0.15 m/yr. We are studying the temporal relationships between mountain-building and climate in this regional setting by using a combined approach of low-temperature apatite (U-Th)/He thermochronometry in the Cascades crystalline rocks themselves, and stable isotope variations in authigenic minerals in clays and carbonates in paleosols of different ages on the dry, east side of the range. In addition, through combined GIS and He dating work, we are examining the relationship between creation of Cascades topographic relief and Pleistocene-to-recent glaciation in the range, and evaluating the role of relatively recent erosional forces on orogenic exhumation. Our preliminary work indicates that He ages record much younger ages than other radiometric systems in the Cascades, suggesting a relatively recent (late Miocene at the earliest) period of exhumation, which is consistent with paleontological evidence from eastern Washington for the lack of a severe climate contrast until this time.