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

约翰·韦斯利·鲍威尔在19世纪末提出的关于大峡谷时代的问题，阐述了大峡谷地区的构造和景观演变以及塑造它的构造事件。最近的论文重振了这场辩论，并支持大峡谷“老”(7000万-1700万年)和“年轻”(500万-600万年)雕刻的模型，以及科罗拉多高原“老”和“年轻”隆起的相应构造模型。支持“老”峡谷模型的研究表明，一条有8000万-7000万年历史的向东流动的河流，然后是一条有5500万-3000万年历史的向西流动的河流，在与现代大峡谷相同的位置和深度切割了一个峡谷。在这种模式下，科罗拉多河在大峡谷的挖掘中并没有发挥重大作用，科罗拉多高原的构造抬升优势发生在大约7000万年前。相比之下，年轻的峡谷模型表明，大峡谷的大部分是在过去600万年内形成的，当时科罗拉多河从落基山脉到加利福尼亚州海湾融为一体，科罗拉多高原地区的隆起经历了多个时期，可能是由于区域地幔上涌而持续的。这个项目测试了大峡谷辩论的“古峡谷决议”，其中有3个“年轻”部分、1个“老”部分和1个“中年”部分，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。两种互补的方法被用来检验这一假设。首先，对每一段的新样品进行磷灰石三重测年(裂变径迹、(U-Th)/He和4He/3He分析)，以重建岩石的冷却路径，并破译过去(现已被侵蚀)的地貌和断层位移。其次，主要保存下来的古遗迹的碎屑锆石和辉长岩测年为校准热年代学研究提供了基本的地面事实。S项目？由于国家和国际公众对大峡谷地区作为地球上标志性的地质特征之一的强烈兴趣而增强了更广泛的意义和重要性。该项目的结果可能会改变目前对大峡谷切割年龄的研究范式。对长达一个世纪的大峡谷争论的讨论和解决表明了科学的方法和进步。该项目将对学生培训、增加地球科学劳动力的多样性、与该地区的美洲原住民部落进行接触、公共非正式科学教育以及加强不同地球科学界之间的协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.