Precise timing and rate of massive late Quaternary soil denudation
Precise timing and rate of massive late Quaternary soil denudation
复制标题
晚第四纪大规模土壤剥蚀的精确时间和速率
DOI：
10.1130/g19749.1
复制
发表时间：
2003
期刊：
影响因子：
5.8
通讯作者：
Rickard S. Toomey
中科院分区：
文献类型：
--
作者：
M. J. Cooke;L. Stern;Jay L. Banner;Lawrence E. Mack;Thomas W. Stafford;Rickard S. Toomey
锶同位素是研究土壤侵蚀动力学的独特工具。Sr同位素比值（87 Sr/ 86 Sr）的变化提供了美国德克萨斯州中部爱德华兹高原晚第四纪景观剥蚀的记录。使用Sr同位素作为土壤侵蚀的示踪剂是基于这样的观察，即在德克萨斯州中部，土壤的87 Sr/ 86 Sr比值与土壤厚度相关。植物和动物表达了土壤中可交换Sr的87 Sr/ 86 Sr比值。因此，我们使用的Sr同位素比值的变化，通过一个很好的年代地层序列的化石植物和动物在霍尔的洞穴，克尔县，得克萨斯州，作为代理土壤厚度的时间变化。通过使用这些记录，我们能够描述晚第四纪气候驱动的土壤侵蚀动力学的爱德华兹Pla-teau。我们发现，以11 cm/k.y.的恒定最小速率，连续侵蚀至少使180 cm的土壤流失;这一连续的侵蚀阶段大约在公元前结束。5 ka。土壤侵蚀的Sr同位素记录是一致的晚第四纪环境变化在得克萨斯州中部已独立建模，使用当地和区域气候记录。然而，这种气候驱动的土壤侵蚀事件的速度比人类土地使用造成的土壤侵蚀慢一个数量级。这些结果将侵蚀与世纪至千年尺度的气候变化联系起来，并警示性地证明，气候变异和人为影响可能会造成更严重的景观退化。
Strontium isotopes are a unique tool to study soil-erosion dynamics. Changes in Sr isotope ratios ( 87 Sr/ 86 Sr) provide a record of late Quaternary landscape denudation of the Edwards Plateau of central Texas, United States. The use of Sr isotopes as a tracer for soil erosion is based on the observation that, in central Texas, the 87 Sr/ 86 Sr ratio of soil correlates with soil thickness. Plants and animals express the 87 Sr/ 86 Sr ratio of exchange- able Sr in the soil. Therefore, we use changes in Sr isotope ratios through a well-dated stratigraphic sequence of fossil plants and animals in Hall's Cave, Kerr County, Texas, as a proxy for temporal changes in soil thickness. By using this record we are able to characterize late Quaternary climate-driven soil-erosion dynamics on the Edwards Pla- teau. We find that continuous erosion removed at least 180 cm of soil at a constant min- imum rate of 11 cm/k.y.; this continuous phase of erosion ended ca. 5 ka. The Sr isotope record of soil erosion is consistent with late Quaternary environmental change in central Texas that has been independently modeled by using local and regional climate records. However, the rate of this climate-driven soil-erosion event was an order of magnitude slower than recent soil erosion caused by human land use. These results link erosion to century- to millennial-scale climate change and are cautionary evidence that even greater landscape degradation may result from coincident climatic variability and anthropogenic influences.