滦河三角洲南部MT04孔磁性地层研究及其构造与气候耦合关系的探讨  

MAGNETOSTRATIGRAPHY AND DISCUSSION OF COUPLING RELATIONSHIP BETWEEN TECTONIC MOVEMENT AND CLIMATE CHANGE OF MT04 BOREHOLE IN SOUTHERN LUANHE RIVER DELTA

作　　者：胥勤勉[1] 袁桂邦[1] 秦雅飞[1] 杨吉龙[1] 杨俊泉[1] 

机构地区：[1]天津地质矿产研究所,天津300170

出　　处：《第四纪研究》2014年第3期540-552,共13页Quaternary Sciences

基　　金：中国地质调查局项目(批准号:1212011120746和1212011120170)资助

摘　　要：对滦河三角洲南部孔深383m的MT04孔进行了详细的岩石磁学和古地磁研究，结果显示：1）孔深0～90m和244～383m沉积物携磁矿物主要为磁铁矿，90～244m沉积物携磁矿物主要为赤铁矿；2）基于208个样品（28个交变样品，180个热退样品）分离出的特征剩磁，建立了钻孔的磁性地层，并与标准极性年表相对比。结果显示，MT04孔记录了Mammoth负极性亚时（C2An．2r）至Brunhes正极性时（C1n）之间的沉积，钻孔M/B界限埋深122．4m，G/M界限埋深为327．2m，钻孔底部年龄约为3．2Ma，而钻孔上更新统底界埋深为83m。MT04孔包括3个沉积阶段：Ⅰ阶段为1．0～3．2Ma，沉积速率平均为92m/Ma，湖相地层为主，为构造稳定期，气候控制了MT04孔的沉积环境和速率；Ⅱ阶段为0．8～1．0Ma，为构造活动期，沉积物以细砂为主，且多为人湖河流和富有机质的粉砂；Ⅲ阶段为0～0．8Ma，构造和气候变化双重作用控制沉积过程，MIS5阶段T3阶地形成之后河流下切，研究区沉积约30m厚连续砂层，且部分层位受海侵影响形成潮控河流；MIS3阶段滦河东流并入青龙河人海，在此沉积约15m厚连续砂层；MIS1阶段滦河摆动至此人海形成典型的两期沙坝一漏湖海岸。The northern coast of Bohai Bay is located within the north of Huanghua Depression which tectonic subsidence can include the rifting episodic in Paleogene, thermal subsidence episodic in Neogene and accelerated thermal episodic in Quaternary. The Quaternary sediment is ca.490m; Late Pleistocene and Holocene sediments are mainly composed of the Luan River delta and alluvial fan of different periods. The northern coast of Bohai Bay acting as the sink of erosion of Yanshan Mountain and the transport of river, can record the uplift of Yanshan Mountain and the subsidence of Bohai Bay basin, and record the climate change in Quaternary. The borehole MT04 is located in the southern Luanhe River delta, and has a length of 383m （39°15＇55＂N, 118°49＇5 I＂E）, and includes 6 units. Rock magnetic studies include x-T, hysteresis loops and isothermal remnant magnetization. Remanence measurements are made using a 2G Enterprises Model 755 three-axis cryogenic magnetometer installed in a magnetically shielded space （〈300nT）. Specimens are thermally demagnetized up to 680℃ using a TD-48 furnace with temperature intervals of 10- 50℃. The other specimens are subjected to alternating field （AF） demagnetization at peak fields up to 70mT with 3-10mT intervals. The results are revealed that ： （ 1 ） magnetite is the major magnetic carrier at the depth interval of 0- 90m and 244-383m, and hematite at the depth interval of 90 - 244m. （2） There are 5 normal magnetozones and 5 reverse magnetozones depend on 208 specimens （ 180 specimens subjected to thermal demagnetization and 28 to alternating field demagnetization） with the characteristic remanent magnetization （ChRM） directions. Comparing with the geomagnetic polarity timescale （Cande et al., 1995; Gradstein et al., 2004）, the normal magnetozones N1, N2, N3, N4 and N5 identified here can be correlated with Cln, Clr. ln, C2n, C2An.ln and C2An.2n, respectively, the reverse magnetozones R1, R2, R3, R4 and R5 can be correlated with Clr. lr, Clr.2

关 键 词：滦河三角洲 第四纪 岩石磁学性质 磁性地层学 

分 类 号：P534.63[天文地球—第四纪地质学] P318.41[天文地球—古生物学与地层学]