{"title":"The Role of Talus Pile Mobility in Valley Widening Processes and the Development of Wide Bedrock Valleys, Buffalo River, AR","authors":"O. H. Groeber, A. L. Langston","doi":"10.1029/2023JF007612","DOIUrl":null,"url":null,"abstract":"<p>Valley width is largely controlled by lithology and upstream drainage area, but little work has focused on identifying the processes through which valleys widen. Bedrock valleys widen by first laterally eroding bedrock valley walls, followed by the collapse of overlying bedrock material that must then be transported away from the valley wall before the valley can continue widening. We hypothesize that talus piles that cannot be transported by the river protect the valley wall and slow valley widening, while talus piles that are rapidly transported allow for uninterrupted valley widening. We used field measurements from 40 locations in both wide and narrow valleys along the Buffalo River, AR to test this hypothesis. Our data show that wide valleys tend to have fewer talus piles and smaller talus grain sizes, whereas talus in narrow valleys is larger in size and more continuous along valley walls. We calculated potential talus block entrainment at each site location and found that talus blocks in wide valleys are potentially entrained and moved away from valley walls during moderate and large flood events, whereas talus blocks in narrow valleys are very rarely moved. Our results show that the potential transport of talus piles protecting bedrock valley walls from widening is controlled by the block size of collapsed bedrock wall material relative to stream competency. Our results also suggest that persistence versus mobility of collapsed talus piles is an important process in the development of wide bedrock valleys.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":null,"pages":null},"PeriodicalIF":3.5000,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JF007612","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geophysical Research: Earth Surface","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2023JF007612","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Valley width is largely controlled by lithology and upstream drainage area, but little work has focused on identifying the processes through which valleys widen. Bedrock valleys widen by first laterally eroding bedrock valley walls, followed by the collapse of overlying bedrock material that must then be transported away from the valley wall before the valley can continue widening. We hypothesize that talus piles that cannot be transported by the river protect the valley wall and slow valley widening, while talus piles that are rapidly transported allow for uninterrupted valley widening. We used field measurements from 40 locations in both wide and narrow valleys along the Buffalo River, AR to test this hypothesis. Our data show that wide valleys tend to have fewer talus piles and smaller talus grain sizes, whereas talus in narrow valleys is larger in size and more continuous along valley walls. We calculated potential talus block entrainment at each site location and found that talus blocks in wide valleys are potentially entrained and moved away from valley walls during moderate and large flood events, whereas talus blocks in narrow valleys are very rarely moved. Our results show that the potential transport of talus piles protecting bedrock valley walls from widening is controlled by the block size of collapsed bedrock wall material relative to stream competency. Our results also suggest that persistence versus mobility of collapsed talus piles is an important process in the development of wide bedrock valleys.
山谷宽度在很大程度上受岩性和上游排水面积的控制,但很少有人关注山谷拓宽的过程。基岩河谷首先通过横向侵蚀基岩谷壁来拓宽,然后是上覆基岩材料的崩塌,在河谷继续拓宽之前,上覆基岩材料必须被运离谷壁。我们假设,无法被河流搬运的滑石堆积物可以保护谷壁,减缓山谷的拓宽,而快速搬运的滑石堆积物则可以使山谷不间断地拓宽。我们利用对 AR 州布法罗河沿岸宽谷和窄谷 40 个地点的实地测量来验证这一假设。我们的数据显示,宽谷中的距石堆往往较少,距石粒径较小,而窄谷中的距石粒径较大,沿谷壁的连续性较强。我们计算了每个地点的潜在滑石块夹带量,发现在中度和大洪水期间,宽谷中的滑石块有可能被夹带并移离谷壁,而窄谷中的滑石块则很少移动。我们的研究结果表明,保护基岩谷壁不被拓宽的距石堆的潜在迁移能力受基岩谷壁坍塌物质的块体大小和溪流能力的控制。我们的研究结果还表明,坍塌距石堆的持久性与流动性是宽基岩谷发展的一个重要过程。