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选择长江扬中段古河谷作为研究对象,探讨末次冰期最盛期以来的沉积环境.搜集整理了扬中—泰州长江大桥地质勘探钻孔28个,根据钻孔资料,绘制了长江古河谷的地质剖面示意图.在其中2个钻孔采集了粒度样品、磁化率样品,分别用Mastersizer 2000激光粒度仪、Bartington MS2磁化率仪进行了分析;在4个钻孔采集了14C年代样品,利用液体闪烁计数仪进行测定,得出了27个年代数据.结果表明:扬中地区长江古河谷约-61 m以上沉积为末次冰期最盛期以来的沉积;末次冰期最盛期、晚冰期早期(约12 000 a B.P.),河流滞留沉积与溯源堆积形成了厚约24 m的河床相砂砾层;-23~-37 m为12 000 a B.P.-8 000 a B.P.时的河漫滩相沉积,沉积物主要为粉砂及粉砂质黏土,局部细砂;8 000 a B.P.-4 000 a B.P.为河口湾环境,形成河口湾-浅海沉积,厚度为-17~-23 m,沉积物主要为粉砂夹粉砂质黏土;-17 m以上为4 000年以来的河口坝、汊道河床沉积及三角洲形成以来的河床、河漫滩沉积.
The Yangtze River middle reaches of the ancient river valley was selected as the research object to discuss the depositional environment since the peak of the last glacial period.The 28 geological exploration drilling holes of Yangzhong-Taizhou Yangtze River Bridge were collected, and the sketch of the geological section of the Yangtze River ancient valley was drawn according to the borehole data. In two of the boreholes, particle size samples and magnetic susceptibility samples were collected and analyzed using a Mastersizer 2000 laser particle size analyzer and a Bartington MS2 magnetic susceptibility meter, respectively. 14C samples were collected from four boreholes and measured using a liquid scintillation counter , And 27 dating data are obtained.The results show that the sediments of about -61 m above the Yangtze River valley in the Yangzhong area have been deposited since the peak of the last glacial period; during the last Ice Age, in the early late glacial period (about 12 000 a BP) Sedimentation and traceability of sediments formed a river bed facies gravel layer of about 24 m thick; river floodplain sediments of -23 ~ -37 m were 12 000 a BP-8 000 a BP, the sediments were mainly silt and silty clay, Local fine sand; 8 000 a BP-4 000 a BP is estuarine environment, forming estuarine-shallow sea sediments with a thickness of -17 ~ -23 m and sediments mainly silty-clouded silty clay; -17 m or more For 4 000 years Since the mouth of the river bed dam, Branch Road and river delta sedimentary formation, floodplain deposits.