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

华盛顿瀑布投下了北美最大的气候雨影之一，西侧的一些地区的年平均降雨量超过4米/年，东侧的降雨量低于0.15米/年。我们正在利用喀斯喀兹结晶岩石本身的低温磷灰石(U-Th)/氦测年和山脉东侧干燥不同时代古土壤中粘土和碳酸盐中自生矿物的稳定同位素变化相结合的方法，研究该区域造山与气候之间的时间关系。此外，通过结合地理信息系统和He测年工作，我们正在研究喀斯特地貌地貌的形成与该山脉更新世至现代冰川作用之间的关系，并评估相对较新的侵蚀力在造山折返中的作用。我们的初步工作表明，他的年龄记录比喀斯喀特地区的其他辐射测量系统要年轻得多，这意味着一个相对较新的(最早是中新世晚期)折返时期，这与华盛顿东部的古生物学证据一致，表明到目前为止没有严重的气候对比。

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.