Palaeogeography and evolution of the Godavari delta, east coast of India during the Holocene: An example of wave-dominated and fan-delta settings
Palaeogeography and evolution of the Godavari delta, east coast of India during the Holocene: An example of wave-dominated and fan-delta settings
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DOI：
10.1016/j.palaeo.2015.09.006
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发表时间：
2015-12
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影响因子：
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通讯作者：
K. N. Rao;Y. Saito;K. Nagakumar;G. Demudu;A. S. Rajawat;Sumiko Kubo;Zhen Li
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文献类型：
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作者：
K. N. Rao;Y. Saito;K. Nagakumar;G. Demudu;A. S. Rajawat;Sumiko Kubo;Zhen Li
通过对2010-2013年间在印度东海岸戈达瓦里三角洲平原采集的11个钻孔岩心和地貌的分析，研究了印度东部沿海哥达瓦里三角洲的全新世演化。哥达瓦里三角洲占地5820平方公里，是世界上最大的以海浪为主的三角洲之一，周围是一片约30公里宽的海滩脊平原。沉积相及其时代分析表明，全新世海相层序向海方向增厚约10米至50米以上，当地相对海平面在10.9-8.0年间迅速上升至低于现今海平面的7.5米，然后缓慢上升至目前的水平。过去6个月沉积速率和古海岸线的时空变化揭示了主要沉积中心(三角洲叶)的连续变化。我们认识到三角洲演化的六个阶段，由撕裂控制的三角洲叶具有明显的循环移位。位于距现在海岸线12-14公里的内陆的线性海滩脊，将前三个叶与后三个叶分开，代表了过去尖顶三角洲叶的海岸侵蚀效应，以及三角洲中部当前的线性海岸线。我们的研究记录了全新世期间在千年到百年时间尺度上的连续净进积。然而，自1970年代以来，大坝建设和引水造成的泥沙排放量大幅减少，加剧了海岸侵蚀，导致戈达瓦里三角洲平原缩小，并使其进入持续破坏阶段。
We investigated the Holocene evolution of the Godavari delta along the east coast of India, by analyses of landforms and 11 borehole cores collected from the delta plain during 2010–2013 with 11314C dates. The Godavari delta covering an area of 5820 km2is one of the world's largest wave-dominated deltas fringed by a ~ 30 km wide beach-ridge plain. Our analysis of sediment facies and their ages indicated that the Holocene marine sequence thickens seaward from ~ 10 m to more than 50 m and that the local relative sea level rapidly rose from 43.5 m to 7.5 m below the present sea level during 10.9–8.0 cal ky BP followed by a slow rise up to its current level around 5 cal ky BP. Spatio-temporal variations in sediment accumulation rates and palaeo-shorelines for the last 6 ky revealed successive changes of the main depocentre (delta lobe). We recognised six stages of delta evolution with distinct cyclic shifts of delta lobes controlled by avulsions. A linear beach ridge located 12–14 km inland from the present shoreline, which separates the first three lobes from the last three, represents the effect of coastal erosion of past cuspate delta lobes, as does the current linear shoreline of the central part of the delta. Our study documents continuous net progradation during the Holocene on millennial to centennial time scales. However, a considerable decrease of sediment discharge due to dam construction and water diversion since the 1970s has exacerbated coastal erosion, resulting in shrinking of the Godavari delta plain and tipping it into a persistent destruction phase.