南京长江大桥附近长江古河谷的形成及沉积特征

末次盛冰期,由于海平面大幅度下降,长江发育古深槽.分析认为,研究剖面附近的深切河槽是局部的深切结果.南京古河谷沉积物,可以分为三期明显的由粗到细的沉积韵律:末次盛冰期深切古河谷,沉积物颗粒粗,从卵砾石到中砂、粗砂;冰后期河床较宽,沉积物从砾石、粗砂到中砂、细砂;全新世,河流进一步展宽,流速变慢,泥沙大量沉积,沉积物从粗砂、中砂到细砂、粉砂,细砂沉积厚度很大.各期河床形态和沉积物的特征,反映了末次盛冰期、冰后期、全新世时期的气候变化和环境演变.

Formation ＆ Sedimentary Characteristics of the Yangtze River Incised-Valley in Nanjing

During the last glaciation maximum, the Yangtze river developed deep incised-valley due to the strong fall of the sea-level. In conclusion, the deep incised-valley in the stratigraphical cross-section was brush-fire. The Yangtze river incised-valley fill in Nanjing is divided into three depositional rhythms of sediment from coarseness to finesse on the basis of the sedimentary grain . During the last glaciation maximum, the deep incised-valley channel bed was narrow and the water discharge decreased . The flow velocity was swift and the sedimentary grain was coarse from gravels to medium, fine sands. During the post-glacial period, the water increased and the sediment ranged from gravel, coarse sands medium sands to fine sands. During Holocene Epoch, the river widened fatherly. The flow velocity became slowly. The sediment including gravels, coarse sands, medium sands and fine sands deposited in great quantities. The fine sandy laminae was very thick. The river bed configuration and the sedimentary characteristics in different stages reflected the climate change and environmental evolution during the last glaciation maximum, the post glacial period and the Holocene.