COLLABORATIVE RESEARCH: Structure of the Mt. Stuart Batho- lith and Its Wall Rocks: Implications for Tilted Plutons and Cretaceous Orogenesis in the North Cascades

对于华盛顿西北部、华盛顿西南部和不列颠哥伦比亚省西南部的白垩纪中期深层造山作用，人们提出了两种截然不同的模式。其一是在格兰格利亚与北美碰撞过程中形成的西北级联冲断系，导致级联结晶核向西逆冲和埋藏。在另一种情况下，造山作用是扭压作用的结果，结晶核是大型右旋剪切带的一部分。关于来自深成岩的古地磁数据是否表明侵入的地体走得很远，或者是否相反，深成岩的倾斜度高达35度，也存在相反的看法。这个项目将考察这座山。斯图亚特岩基及其周围围岩，它们相对于西北瀑布逆冲系统和结晶核占据着关键位置。这项工作将涉及测绘、运动学分析和无线电测量年代测定。这些结果旨在确定该地区的倾斜量，以及岩体侵位和区域形变如何随深度变化。杰出模型之间的分辨率将对西北构造产生重大影响。

Two fundamentally different models have been proposed for profound mid-Cretaceous orogenesis in northwestern Washington and southwestern Washington and southwestern British Columbia. In one, the northwest Cascade thrust system formed during the collision of Wrangellia with North America, and resulted in west- directed thrusting and burial of the Cascades crystalline core. In the other, orogenesis was the result of transpression and the crystalline core was part of a large dextral shear zone. Contro- versy also exists regarding whether paleomagnetic data from plutons indicate that the intruded terranes are far travelled or if instead the plutons have been tilted up to 35o. This project will examine the Mt. Stuart batholith and surrounding wall rocks which occupy a key position relative to the northwest Cascades thrust system and the Crystalline core. The work will involve mapping, kinematic analysis and radio- metric dating. Results are aimed at determining the amount of tilting in the region and how pluton emplacement and regional deformation change with depth. Resolution between outstanding models will have considerable implications for northwest tectonics.