Collaborative Research: The Age of Grand Canyon: Applying New Tests to Resolve the 150-year-old Debate

约翰·韦斯利·鲍威尔（John Wesley Powell）在19世纪后期提出了有关大峡谷年龄的问题，涉及大峡谷地区的构造和景观演变，以及形成大峡谷的构造事件。最近的论文重新激起了争论，并支持大峡谷“老”（7000 - 1700万年）和“年轻”（500 - 600万年）的雕刻模型，以及相应的科罗拉多高原“老”和“年轻”隆起的构造模型。支持“古老”峡谷模型的研究表明，一条8000万至7000万年前向东流动的河流，然后是一条5500万至3000万年前向西流动的河流，在同一位置切割出一个峡谷，其深度与现代大峡谷几乎相同。在这个模型中，科罗拉多河对大峡谷的挖掘作用并不显著，科罗拉多高原的构造隆升优势发生在大约7000万年前。相比之下，“年轻”峡谷模型表明，大峡谷的大部分是在过去600万年里形成的，当时科罗拉多河从落基山脉与加利福尼亚湾融合在一起，科罗拉多高原地区的隆起发生了多次，并且可能由于区域地幔上升流而持续进行。该项目测试了大峡谷争论的“古峡谷分辨率”，其中有3个“年轻”段，1个“老”段和1个“中间”年龄段，它们共同提供了美国西南部复杂的多阶段构造隆升历史的记录。首先，将磷灰石三重定年（裂变径迹、(U-Th)/He定年和4He/3He分析）应用于每个片段的新样品，以重建岩石的冷却路径，并破译过去（现在已被侵蚀）的景观和断层位移。其次，关键保存的古河流遗迹的碎屑锆石和水晶石定年为校准热年代学研究提供了必要的基础事实。这个项目吗?美国国内和国际公众对大峡谷地区作为地球的一部分的强烈兴趣，增强了它更广泛的意义和重要性。S标志性的地质特征。该项目的结果可能会改变目前关于大峡谷切口年龄的范式。长达一个世纪的大峡谷之争的讨论和解决说明了科学的方法和科学的进步。该项目将对学生培训、增加地球科学工作人员的多样性、向该地区的美洲土著部落推广、公共非正式科学教育以及促进不同地球科学社区之间的合作进展产生重大影响。

Questions about the age of Grand Canyon, framed by John Wesley Powell in the late 1800s, address the tectonic and landscape evolution of the Grand Canyon region and the tectonic events that have shaped it. Recent papers reinvigorate the debate, and support models for both "old" (70-17 million years) and "young" (5-6 million years) carving of Grand Canyon, with corresponding tectonic models for "old" versus "young" uplift of the Colorado Plateau. Studies supporting the "old" canyon model suggest that an 80-70 million year old east-flowing river, then a 55-30 million year old west-flowing river, incised a canyon in the same location and to nearly the same depth as modern Grand Canyon. In this model, the Colorado River did not play a significant role in excavating Grand Canyon, and the preponderance of tectonic uplift of the Colorado Plateau took place about 70 million years ago. In contrast, "young" canyon models suggest that most of the Grand Canyon has been carved in the last 6 million years once the Colorado River became integrated from the Rocky Mountains to the Gulf of California and that uplift of the Colorado Plateau region has taken place in multiple episodes and may be ongoing due to regional mantle upwelling. This project tests a "paleocanyon resolution" for the Grand Canyon debate in which there are 3 "young" segments, 1 "old" segment, and 1 "intermediate" age segment that collectively provide a record of a complex multi-stage tectonic uplift history for the southwestern U.S. Two complementary methods are used to test this hypothesis. First, apatite triple dating (fission track, (U-Th)/He dating, and 4He/3He analyses) are applied to new samples from each segment to reconstruct cooling paths for rocks and decipher past (now-eroded) landscapes and fault displacements. Second, detrital zircon and sanidine dating of key preserved paleoriver remnants provide essential ground truth to calibrate the thermochronological investigations.The project?s broader significance and importance are enhanced by intense national and international public interest in the Grand Canyon region as one of Earth?s iconic geologic features. The results of this project may change the current paradigm for the incision age of the Grand Canyon. Discussion and resolution of the century-long Grand Canyon debate illustrates the scientific method and progress of science. The project will have significant impacts on student training, increased diversity of the geoscience workforce, outreach to Native American tribes in the region, public informal science education, and increased collaborative progress among diverse geosciences communities.