雅鲁藏布江高能洪水沉积特征及地貌效应

青藏高原东南缘雅鲁藏布江流域的气候、水文、构造与地形条件具有发育超大冰川或滑坡堰塞湖及高能洪水的潜力。对高能洪水沉积特征的研究进展进行简要回顾,以青藏高原雅鲁藏布江流域广泛分布的高能洪水地貌和沉积证据为主要研究对象,探讨了该流域高能洪水沉积物的主要沉积特征及其形成原因,最后对该流域高能洪水的地貌效应进行了简要分析。结果表明:雅鲁藏布江流域高能洪水形成的巨型边滩以涡流型边滩居多,其次为点状边滩和吊坠型边滩,未见牵引型边滩; 就沉积特征而言,该流域高能洪水巨型边滩的内部沉积以水平叠层为主,波纹及交错层理层、粉砂层、斜坡沉积和粗砾平行层理层亦见分布; 高能洪水等极端地表过程在青藏高原及雅鲁藏布江的泥沙输移及地貌演变中发挥着关键作用。

Sedimentological Characteristics and Geomorphic Effect of Megaflood in Yarlung Tsangpo River,China

The climatic, hydrological, tectonic and topographic conditions of the Yarlung Tsangpo river basin in the southeastern margin of the Tibetan Plateau have the potential to develop super-large reservoir glaciers or landslide-dammed lakes that result in megafloods. The research progresses in the sedimentary characteristics of megafloods were briefly reviewed; by presenting widely distributed geomorphology and sedimentary evidence of megafloods in the Yarlung Tsangpo river basin, the main sedimentary characteristics and causes of megaflood sediments in the basin as well as their geomorphological response in the basin were summarized. The results show that eddy bars are the most common ones in the Yarlung Tsangpo river basin, followed by point bars and pendant bars, but expansion bars are absent; in terms of sedimentary characteristics, the well-sorted, horizontally laminated silt and coarse sand or granules are predominant in the internal sedimentary structure of giant bars; special sedimentary structures, including typical ripple and cross-lamination, silt bed, clinoforms and coarse parallel bedding can also be found sometimes. The evidence and previous studies show that extreme surface processes such as megafloods play a key role in sediment transport and landscape evolution over the Tibetan Plateau and the Yarlung Tsangpo river basin.