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首页> 外文期刊>Earth-Science Reviews: The International Geological Journal Bridging the Gap between Research Articles and Textbooks >Three-dimensional evolution of the Yangtze River mouth, China during the Holocene: impacts of sea level, climate and human activity
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Three-dimensional evolution of the Yangtze River mouth, China during the Holocene: impacts of sea level, climate and human activity

机译：全新世期间长江口的立体演变：海平，气候和人类活动的影响

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The Yangtze (Changjiang) mega-delta, China, has a high risk of coastal erosion owing to the recent high rate of relative sea-level rise and reduced sediment supply. The study of the Holocene evolution of the delta can provide information about its response to rapid sea-level rise and changes in sediment supply caused by climate or human activity, although this has yet to be fully explored because of the lack of integrated studies using age constrained sedimentary records. Here we document stratigraphic architecture and morphological changes over the last 11,700 years and estimate the amount of sediment trapped in the delta region on a millennial scale using a dataset of 344 sediment cores, 658 radiocarbon and 28 optically stimulated luminescence (OSL) ages (of which we obtained 64 cores, 345 radiocarbon and 28 OSL ages, and the others we sourced from the literature). Using this dataset we present the temporal and spatial morphodynamic evolution of the entire Yangtze River mouth from its early Holocene transgressive estuary to a mid- to late-Holocene regressive delta, making it possible to produce a quantitative and sequential analysis of sediment deposition. A destructive phase of the river mouth region was identified at 10 to 8 cal. kyr BP, including significant coastal erosion of tidal flats and troughs within the estuary and of tidal ridge-and-trough topography offshore; these resulted from the reshaping of the river mouth morphology caused by rapid sea-level rise at that time. As a result, the rate of sediment trapping at the river mouth declined from an average of 224 Mt yr(-1) at 11.7-10 cal. kyr BP to 137 Mt yr(-1) between 10 and 8 cal. kyr BP. Since delta initiation 8000 years ago, a retreat of the subaqueous delta occurred and the sediment trapping rate declined from 151 Mt yr(-1) at 8-6 cal. kyr BP to 99-113 Mt yr(-1) between 6 and 2 cal. kyr BP, caused by the reduction in sediment supply linked to summer monsoon weakening similar to 6000 years ago. In the last 2000 years the sediment trapping rate has increased to 162 Mt yr(-1) due to intensified human activity. The present-day level of sedimentation in delta (49 Mt yr(-1) in 2003-2011), after the completion of the Three Gorges Dam, is far lower than the 'natural' range in the Holocene. We thus infer a potential for system regime shift in terms of coastal erosion and a transition to a new equilibrium in delta morphology in the near future.
机译：中国近期梅格塔（长江）旺泽（长江）近期侵蚀风险很高，近期相对海平升高和降低沉积物供应。达特拉全新世演化的研究可以提供关于其对快速海平面上升和气候或人类活动引起的泥沙供应变化的信息，尽管由于使用年龄缺乏综合研究尚未完全探索。受限沉积记录。在这里，我们在过去11,700年内记录地层架构和形态变化，并估计使用344沉积物核，658 radiocarbon和28个光学刺激的发光（OSL）年龄（其我们获得了64个核心，345个radiocarbon和28岁，我们来自文学的其他人）。使用此数据集我们从其早期的海滨近期回归三角洲到了整个长江口的时间和空间形态动力学演变，使得可以产生对沉积物沉积的定量和顺序分析。河口区域的破坏性阶段在10至8分钟内鉴定出来。 Kyr BP，包括潮汐公寓的显着沿海侵蚀，河口和潮汐岭和槽地形近海地区;这些是由于当时快速海平面上升引起的河口形态的重塑。结果，河口陷阱的沉积物速度从11.7-10克拉的平均平均224毫升（-1）下降。 KYR BP至137 MT YR（-1）在10到8克之间。 kyr bp。由于δ发起8000年前，发生了亚水δ的撤退，并且沉积物诱捕率从8-6次CAL的151毫升（-1）下降。 KYR BP至99-113 MT YR（-1）在6到2次CAL之间。 KYR BP，由沉积物供应的减少引起，与夏季季风削弱相似，与6000年前相似。在过去的2000年中，由于人类活动强化，沉积物捕获率增加到162吨（-1）。三层峡谷完成后，三角洲（49吨YR（-1）沉淀的现状水平（49吨（-1），远低于全新世的“自然”范围。因此，我们在不久的将来推断了在沿海侵蚀方面的系统制度转变和转型到迄今为止在Delta形态的新均衡的转变。

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