Holocene flood histories in south‐western USA
Holocene flood histories in south‐western USA
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DOI：
10.1002/esp.1983
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发表时间：
2010-05
影响因子：
3.3
通讯作者：
T. Harden;M. Macklin;V. Baker
中科院分区：
文献类型：
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作者：
T. Harden;M. Macklin;V. Baker
美国西南部的河流流域是世界上研究最广泛的干旱陆地河流系统之一。自20世纪60年代初以来，他们的水文气候历史已经从冲积物切割和填充循环的分析中重建，而从20世纪70年代末开始，人们对稳定边界基岩河段的淡水沉积物和大洪水的古阶段指标进行了调查。然而，目前还没有研究将这两种不同类型河流环境的全新世河流史进行区域整合。目前的研究将冲积档案与基岩流域的洪水记录结合起来，以概率为基础，生成了美国西南部12000年的洪水记录。使用700多个14C年代的河流单元，分析产生了一个高分辨率（百年）的洪水记录。在11,250-10,400、8800-8350、8230-7600、6700-5700、5600-4820、4550-3320和2000-0 cal. BP发生了7次洪水增加。发现基岩河段在全新世中后期记录了更频繁的洪水，而冲积河则在全新世早期和中期记录了更多的洪水单元。这些差异主要是选择性保存的结果，在以特大洪水为特征的时期，冲积河段容易受到侵蚀。在基岩系统内的静水沉积物中记录的全新世大洪水事件与该地区降水增加和温度降低的时期相对应。相比之下，在冲积河流中，高于平均水平的洪水概率，以及区域广泛的河道壕沟事件，与年降水量减少和温度降低相匹配。本研究的结果清楚地证明了全新世河流档案在重建美国西南部区域、短期水文气候变化方面的价值。版权所有©2010 John Wiley & Sons， Ltd
River basins in south‐western USA are some of the most extensively studied arid land fluvial systems in the world. Since the early 1960s their hydro‐climatic histories have been reconstructed from the analysis of alluvial cut‐and‐fill cycles, while from the late 1970s there have been investigations of slackwater deposits and palaeostage indicators for large floods in stable‐boundary bedrock reaches. However, no studies have regionally integrated Holocene fluvial histories from these two different types of fluvial environments. The current study combines the alluvial archive with flood records from bedrock reaches to generate a probability‐based 12,000 year record of flooding in south‐western USA. Using more than 700 14C‐dated fluvial units, the analysis produces a high resolution (centennial) flood record. Seven episodes of increased flooding occurred at 11,250–10,400, 8800–8350, 8230–7600, 6700–5700, 5600–4820, 4550–3320 and 2000–0 cal. BP. Bedrock reaches are found to record more frequent floods during the middle to late Holocene, while in alluvial rivers more flood units are dated to the early and middle Holocene. These differences are primarily the result of selective preservation with alluvial reaches tending to erode during periods characterised by very large floods. Episodes of major Holocene flooding recorded in slackwater deposits within bedrock systems correspond with periods of increased precipitation in the region and lower temperatures. In contrast, within alluvial rivers above‐average flooding probabilities, as well as regionally extensive channel entrenchment episodes, match with reduced annual precipitation and lower temperatures. The results of this study clearly demonstrate the value of the Holocene fluvial archive for reconstructing regional, short‐term hydro‐climatic change in south‐western USA. Copyright © 2010 John Wiley & Sons, Ltd.