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ISSN 2096-7780 CN 10-1665/P

长江冲积平原铜陵市BZK1孔岩性特征及第四系地层划分

Lithological characteristics and Quaternary stratigraphic classification of the BZK1 drill core in Tongling in the Yangtze River alluvial plain

  • 摘要: 第四纪地层划分是研究第四纪环境演变过程的重要基础,也可为浅层地震勘探剖面的反射层位标定和地质解释提供有效的标尺,是城市活断层及地震危险性评价的基础工作。通过分析铜陵市义安区西联镇犁桥村BZK1孔岩芯中总厚度78 m的第四纪沉积物的岩性、颜色、物质组成、沉积结构等特征,并在对地层进行详细分层的基础上,综合采用光释光、电子自旋共振等年代测试,建立了BZK1孔的第四纪地层年代标尺。通过对第四纪沉积物的粒度分析,对区域沉积环境进行了分析研究。BZK1钻孔岩芯自下而上整体揭示了中更新世早期冲洪积相(埋深56.7~76.2 m)、晚更新世河流相(埋深35.0~56.7 m)和全新世河漫滩相(埋深0~35.0 m)地层沉积序列,缺失了早更新世及中更新世中晚期沉积的地层。BZK1钻孔第四纪地层格架的建立,可为铜陵市活动断层探测人工地震勘探及钻孔联合剖面探测提供有效的地质标尺,也可为长江冲积平原第四纪地层对比、年代地层划分及沉积环境演化等提供相应依据。

     

    Abstract: The stratigraphic classification of the Quaternary strata in the Yangtze River alluvial plain provides a fundamental basis for reconstructing the evolution of the Quaternary environment and serves as an effective standard for calibrating reflection layers and interpreting shallow seismic profiles. It also provides a basis for studies of active urban faults and seismic hazard assessments. In this study, we examined the lithology, color, material composition, sedimentary structures, and other characteristics of the 78 m thick Quaternary succession from Liqiao Village, Xilian Town, Yi’an District, Tongling City, China using the BZK1 drill core. Based on the detailed stratigraphic subdivision, a Quaternary age framework for the BZK1 core was established using a combination of optically stimulated luminescence and electron spin resonance dating techniques. Grain size analysis was conducted to investigate the regional sedimentary environment. The BZK1 core recorwds, from bottom to top, early Middle Pleistocene alluvial deposits (56.7~ 76.2 m), Late Pleistocene fluvial deposits (35.0~ 56.7 m), and Holocene floodplain deposits (0~ 35.0 m), but lacks deposits from the Early Pleistocene and the Middle to Late Middle Pleistocene. The establishment of the Quaternary stratigraphic framework for the BZK1 drill core provides a reliable geological reference for active fault detection, artificial seismic exploration, and integrated borehole profile interpretation in Tongling City. It also offers a valuable basis for regional Quaternary stratigraphic correlation, chronostratigraphic subdivision, and the reconstruction of the sedimentary environmental evolution in the Yangtze River alluvial plain.

     

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