美国犹他州立大学 Natalie M. Tanski 团队在研究美国犹他州峡谷地带的科罗拉多阶地中取得新进展。他们表明，该地带记录了更新世期间不稳定的盐构造对瀑布峡谷裂隙带的短暂切割和生长。相关论文发表在2023年11月20日出版的《地质学》杂志上。

研究人员称，在大瀑布峡谷上游、沿河曲峡谷的地层阶地中，发光和宇宙成因核素年龄支持的该阶地上的场相关性，揭示了在过去约 340 k.y.，以平均速率约为 0.4 mm/kr 的速率不稳定切割的复杂记录。上游快速切口的进展和独特的S型长剖面阶地模式表明，切口是对间歇性基线下降的反应。此外，阶地与瀑布峡谷上方异常低坡度的现代河道在下游汇合。研究人员将这些结果解释为，至少自中更新世以来，大瀑布峡谷裂隙带的生长，是由于侵蚀—盐构造反馈造成的，这种反馈赋予了一个不稳定、且目前升高的局部基线面。更广泛地说，峡谷地带的特点是快速而不稳定的切割，即使在没有任何区域性或地幔驱动的隆升的情况下，这种切割因局部地质的控制而变得复杂。

据了解，在犹他州东南部的峡谷地带的科罗拉多河阶地，可以进行年代测定和分析，来解决科罗拉多高原最大的河道陡度异常—瀑布峡谷的切割和性质的控制问题。

附：英文原文

Title: Pleistocene Colorado River terraces in the canyonlands region (Utah, USA) record unsteady, transient incision and growth of the Cataract Canyon knickzone by salt tectonics

Author: Natalie M. Tanski, Joel L. Pederson, Tammy M. Rittenour, Alan J. Hidy

Issue&Volume: 2023-11-20

Abstract: Colorado River terraces in the canyonlands region of southeastern Utah can be dated and analyzed to address the controls of incision and nature of the Colorado Plateau's largest channel-steepness anomaly, Cataract Canyon. Field correlations supported by luminescence and cosmogenic-nuclide ages on strath terraces along Meander Canyon, upstream of Cataract Canyon, reveal a complex record of unsteady incision over the past ～340 k.y. at an average rate of ～0.4 mm/yr. Both an upstream progression of rapid incision and a unique sigmoidal long-profile pattern of terraces indicate incision in response to episodic baselevel fall. Also, terraces converge downstream with the anomalously low-gradient modern channel above Cataract Canyon. We interpret these results as indicating that growth of the Cataract Canyon knickzone is due to an erosion-salt tectonics feedback since at least the Mid Pleistocene, which has imparted unsteady, and currently elevated, local baselevel. More broadly, the canyonlands region is marked by rapid and unsteady incision that is complicated by local geologic controls even while being absent of any regional or mantle-driven uplift.

DOI: 10.1130/G51599.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51599.1/629716/Pleistocene-Colorado-River-terraces-in-theredirectedFrom=fulltext