Collaborative Research: Mesoproterozoic Tectonics of Inboard Laurentia: Insight Into Assembly and Configuration of Rodinia

该项目正在研究美国西部的中元古代（1300-1000 Ma）沉积岩，以测试有争议的Rodinia假说的各个方面。正在测试的假设是，沉积和构造在西南劳伦特的内侧记录，保存在暴露良好的沉积序列，可用于了解应力在周围的板块边缘，性质的排水模式和盆地在西南劳伦特，和年龄可能的舷外碎屑源。 该研究包括构造、岩石学和地质年代学研究，旨在对比几个关键地区和单位，并描述其物源。这些地区代表了曾经更广泛的沉积序列的残留物;它们暴露良好，但相距甚远，缺乏可靠的地质年代学阻碍了相关性。研究集中在阿帕奇群（亚利桑那州），温卡群（大峡谷），水晶泉组（死亡谷）和拉诺拉组（得克萨斯州）。研究人员正在重建区域内克拉通盆地和构造模式，并寻找可能的外部碎屑来源的“指纹”。年代学研究包括：灰层精确U-Pb年代学定年、碎屑锆石U-Pb年代学、独居石微探针原位U-Pb年代学和云母Ar-Ar激光年代学。沉积构造研究通过寻找断层之间的相变和同构造岩浆活动的关系来评估沉积期间哪些断层是活跃的。岩石学研究强调使用标准岩石学技术的硅质岩的来源。详细的区域测试，涉及地质年代学与沉积构造相联系，提供了更好的了解西部劳伦提斯的构造环境，因此最有可能相邻的外侧大陆块碰撞劳伦提斯从1.3-1.0 Ga。

This project is investigating Mesoproterozoic (1300-1000 Ma) sedimentary rocks in the western U.S. to test aspects of the controversial Rodinia hypotheses. The hypothesis being tested is that the inboard record of sedimentation and tectonics in southwestern Laurentia, preserved in well-exposed sedimentary successions, can be used for understanding stresses at the surrounding plate margins, nature of drainage patterns and basins in southwestern Laurentia, and the age of possible outboard sources of detritus. The research involves structural, petrologic, and geochronologic study aimed at correlation of, and characterizing provenance for, several key areas and units. These areas represent preserved remnants of once more extensive sedimentary successions; they are well exposed, but widely separated, and correlations have been hampered by a lack of reliable geochronology. The study concentrates on the Apache Group (Arizona), Unkar Group (Grand Canyon), Crystal Spring Formation (Death Valley), and Lanora Formation (Texas). The researchers are reconstructing the regional intracratonic basinal and tectonic patterns and searching for a "fingerprint" of possible outboard sources of detritus. The geochronological studies involve: dating ash beds using precise U-Pb geochronology, U-Pb dating of detrital zircons, new in situ U-Pb microprobe dating of monazite grains, and Ar-Ar laser dating of mica grains. Sedimentary-tectonic studies are evaluating which faults were active during deposition by looking for facies changes across faults and relationships to syntectonic magmatism. Petrologic studies are emphasizing provenance of siliciclastic rocks using standard petrologic techniques. Detailed regional tests involving geochronology linked to sedimentary tectonics are providing better understanding of the tectonic setting of western Laurentia and hence the most likely adjacent outboard continental masses that collided with Laurentia from 1.3-1.0 Ga.