美国俄勒冈大学Matthew C. Morriss团队近日通过洞穴记录揭示了北美最深峡谷的最近起源。该研究于2025年5月19日发表在《美国科学院院刊》杂志上。
研究组探索了北美最深的河谷地狱峡谷（约2400米深）是如何形成的，以及何时形成的，解决了W.Lindgren首次提出的这些基本问题[俄勒冈州蓝山黄金带（1901）]。由于缺乏对峡谷的直接约束和地貌分析，关于峡谷形成和切割时间的现有假设仍然是推测性的。研究组结合了洞穴河流沉积物的宇宙成因核素定年、河流剖面分析和数值模拟，首次对地狱峡谷的切割过程进行了直接的年龄约束和系统分析。研究结果表明，在约2.1±1.0 Ma时，一个显著的排水捕获触发了快速切割，建立了蛇河进入哥伦比亚河系统的现代路线。
流域面积的增加和随后溪流功率的增加导致了Hells峡谷的快速切割，并形成了支流断点（KPs），这些断点在远离捕获位置的地方海拔降低。洞穴沉积物的宇宙成因定年表明，切割速率从~0.01 mm y-1增加到~0.16 mm y-1。河流捕获的数值模拟支持了这些观察结果，展示了流域面积的突然增加是如何驱动河流快速切割的。研究组在地狱峡谷的发现提供了一个很好的例子，说明排水捕获如何极大地塑造了一个主要河谷的演变。
附：英文原文
Title: Cave records reveal recent origin of North America’s deepest canyon
Author: Morriss, Matthew C., Mitchell, Nate A., Yanites, Brian J., Staisch, Lydia M., Korup, Oliver
Issue&Volume: 2025-5-19
Abstract: We explore how and when Hells Canyon, North America’s deepest river gorge (~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 ~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 ~0.01 to ~0.16 mm y1. 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.
DOI: 10.1073/pnas.2413069122
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2413069122