Cave records reveal recent origin of North America's deepest canyon

• 成果类型: Article
• 署名作者: Morriss, Matthew C.; Mitchell, Nate A.; Yanites, Brian J.; Staisch, Lydia M.; Korup, Oliver
• 署名单位: University of Oregon; Indiana University System; Indiana University Bloomington; United States Department of the Interior; United States Geological Survey; University of Potsdam; University of Potsdam
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12455
• DOI: 10.1073/pnas.2413069122
• 发表日期: 2025-05-27
• 关键词: cosmogenic al-26; topographic analysis; short communication; colorado plateau; late miocene; river; incision; uplift; EVOLUTION; HISTORY

摘要

We explore how and when Hells Canyon, North America's deepest river gorge (similar to 2,400 m deep), formed, addressing these fundamental questions first posed by W. Lindgren [The Gold Belt of the Blue Mountains of Oregon (1901)]. Existing hypotheses about the canyon's formation and timing of incision remain speculative due to a lack of direct constraints and geomorphic analysis in the canyon. Herein, we combine cosmogenic nuclide dating of cave-bound river deposits, river profile analysis, and numerical modeling to provide the first direct age constraints and systematic analysis of incision processes at work in Hells Canyon. Our study reveals a significant drainage capture triggered rapid incision at similar to 2.1 +/- 1.0 Ma, establishing the Snake River's modern route into the Columbia River system. The increased drainage area and subsequent increase in stream power resulted in the rapid incision of Hells Canyon and the formation of tributary knickpoints (KPs) that decrease in elevation away from the capture location. Cosmogenic dating of cave deposits indicates incision rates increased from similar to 0.01 to similar to 0.16 mm y(-1). Numerical modeling of the stream capture supports these observations, demonstrating how abrupt drainage area increase drives rapid river incision. Our findings from Hells Canyon provide a well-constrained example of how drainage capture can dramatically shape the evolution of a major river gorge.