近日，美国马萨诸塞大学Karin E. Lehnigk及其团队探究了米苏拉洪水的时间。这一研究成果于2024年9月9日发表在国际顶尖学术期刊《地质学》上。

据介绍，美国华盛顿东部的槽状疤地斯卡伯兰是由密苏拉冰川湖爆发的洪水形成的。尽管在研究其年代上有所进步，但其主要洪道侵蚀的时间仍未确定。尤其是最大的槽状疤地峡谷—大古力上峡谷，是否在末次冰期期间还是之前被切割的还不确定。

研究报告了大古力上游、哥伦比亚冰川湖和周围洪水路线的不稳定物的¹⁰Be暴露年龄。大古力山脉东缘高海拔地区洪水搬运的巨砾可以追溯到大约17-15ka.。来自大古力湖底巨砾的年龄表明，后来的ca.14ka时期的洪水形成晚于峡谷切割，发生在15-14.5ka.加利福尼亚州Telford-Crab Creek疤地被洪水淹没之后。

先前的水力模型和年代测定表明，大古力的入口被岩石堵塞，峡谷的切口在大约17ka.时期并不完整；因此，研究人员将东缘17-15ka.暴露年龄解释为与峡谷切割时期一个后退的瀑布的水流相吻合。研究结果表明，大古力的切割形成于17ka-14ka之间。峡谷切割的短暂持续的时间表明，米苏拉冰川湖经历了地球历史上一些最具侵蚀性的爆发洪水。

附：英文原文

Title: The timing of Missoula floods: Implications for the age of Grand Coulee (eastern Washington, USA)

Author: Karin E. Lehnigk, Isaac J. Larsen, Brendon J. Quirk, Scott. R. David

Issue&Volume: 2024-09-09

Abstract: The Channeled Scabland of eastern Washington (USA) was formed by outburst floods from glacial Lake Missoula. Despite chronological advances, the timing of erosion in the main flood channels is unresolved. In particular, it is still uncertain whether upper Grand Coulee, the largest canyon in the Channeled Scabland, was incised during or prior to the last glaciation. We report 10Be exposure ages from erratics in upper Grand Coulee, glacial Lake Columbia, and surrounding flood routes. Flood-transported boulders on the high-elevation east rim of Grand Coulee date to ca. 17-15 ka. Ages from boulders on the floor of Grand Coulee indicate later flooding at ca. 14 ka, which post-dated canyon incision and occurred after inundation of the Telford-Crab Creek scabland at ca. 15-14.5 ka. Prior hydraulic modeling and dating suggest the entrance to Grand Coulee was blocked by rock and that canyon incision was incomplete at ca. 17 ka; hence, we interpret the 17-15 ka exposure ages on the east rim to coincide with flow over a retreating cataract during canyon incision. Our results indicate incision of Grand Coulee was completed between 17 ka and 14 ka. The short duration of canyon incision suggests that glacial Lake Missoula generated some of the most erosive outburst floods in Earth’s history.

DOI: 10.1130/G52505.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52505.1/648331/The-timing-of-Missoula-floods-Implications-for-theredirectedFrom=fulltext