来自1 4C、δ1 3C、粒度和地球化学元素的分析表明,南京江北地区在5 12 0 a BP、6 2 4 0 a BP、4 84 0 a BP和8914 a BP是气候相对暖湿期,而85 2 3a BP和6 5 2 0 a BP可能对应的是相对干冷的气候。该区在94 90～4 84 0 a BP期间沉积速率具有明显不均一性,94 90～8730 a BP期间沉积速率为5 6 m m / 10 0 a,86 95～85 6 6 a BP期间为6 2 m m /10 0 a,而85 2 3～4 84 0 a BP期间沉积速率仅为8m m / 10 0 a,上述现象可能与94 90～85 6 6 a BP期间该区经历过海侵和地壳沉降加快有关。由于在第5～7层中未发现海相有孔虫,可以肯定该区海拔高于7m的地带在94 90～4 84 0 a BP期间未受海侵影响。
Based on the principle that the present is the key to the past , detailed analyses, such as AMS 14C dating, grain size, component and morphology of heavy minerals, micro-morphology of zircon, Rb/Sr, magnetic susceptibility and total organic carbon (TOC), were conducted to identify paleoflood sediments archived in Zhongba Site. The results indicate that the plaeoflood sediments bear great similarities with modern flood sediments in the following aspects: (1) probability cumulative curves mainly show a pattern of 3―4 segments; (2) grain-size distribution of suspended matter ranges between 3 and 10Ф; (3) the sediments are well-sorted, most of which are suspended matter (>50%); (4) the same species, quantity and morphology of heavy minerals; (5) scanning electronic microscope images show that shapes of zircon are mainly oval and nearly spheral, rounded due to long-distance transport; (6) higher Rb/Sr values (0.55―0.66)than those of sediments from cultural layers (0.03―0.26); (7) magnetic susceptibility values (133.73―433.05 10-6m3/kg) are lower than those of sediments from cultural layers (959.25―2442.44 10?6 m3/kg); (8) TOC (0.14%―0.33%) are lower than those of sediments from cultural lay-ers (1.13%―2.95%). Our results demonstrate that, except for the 1981 flood, there are at least six paleoflood events that occurred during the Qing Dynasty, the middle of Song Dy-nasty, the early Warring States (400BC―350BC), the West Zhou Dynasty (920BC―900BC), the Xia Dynasty (2070BC―1600BC), and the late Neolithic Age (3000BC―2300BC), respectively .
ZHU ChenZHENG ChaoguiMA ChunmeiSUN ZhibinZHU GuangyaoWANG HuilinGAO HuazhongWANG PenglingHUANG Run
