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南京江北地区全新世沉积与古洪水研究
HOLOCENE DEPOSITS AND PALEOFLOODS ON THE NORTH BANK OF THE YANGTZE RIVER, NANJING AREA
【摘要】 根据区域调查和对南京江北剖面沉积物及埋藏古树和炭化木的年代测定,以及对孢粉、粒度、石英砂表面特征鉴定分析,发现本区存在晚北方期至亚北方气候期(8200±126aBP、7822±250aBP~7670±160aBP、7562±90aBP、4085±95aBP~4090±100aBP以及3730±90aBP)具有洪积特征的天然剖面地层,该剖面位于长江北岸二级阶地上,其洪积层系由古洪水期长江摆动时沉积所致。剖面上部厚0.53m的灰黄色土层系在亚北方期大约3000aBP~2850aBP的寒冷期中主要由风尘搬运堆积所致。
【Abstract】 ield investigations and analyses of sediments, buried paleotrees, gagatite, sporopollen, granularity, quartzsand surface feature, oxide and chronology found a natural profile with pluvial characteristics during the Lateboreal phase to Subboreal phase (8 200±126 aBP, 7 822±250 aBP~7 670±160 aBP, 7 562±90 aBP, 4 085±95 aBP~4 090±100 aBP and 3 730±90 aBP). The sporopollen with more thermophilous coniferousbroad plant communities in the profile illustrates that the humidhot climate should be a major climate during the period from 8 200±126 aBP to 3 730±90 aBP. A large number of agatite, buried paleotrees and sandgravel with pluvial feature between the third layer and the ninth layer indicate that the period has experienced many times flood environments with megathermal pluvial climate. The investigation shows that the profile is situated in the second terrace on the north bank of the Yangtze River, its pluvial layer should be formed by the Yangtze River swinging and depositing during the paleoflood period. In addition, the greyyellow loess layer with thickness of 0.53m in the upper of the profile should be formed by dust transporting and accumulation during the cold period (3 000 aBP~2 850 aBP) of Subboreal phase by the analyses.
【Key words】 north bank of the Yangtze River of Nanjing area; Holocene; paleofloods; climatic abnormal event;
- 【文献出处】 地理研究 ,GEOGRAPHICAL RESEARCH , 编辑部邮箱 ,1997年04期
- 【分类号】P531
- 【被引频次】69
- 【下载频次】630