吕梁山西麓复兴剖面红黏土的磁性地层学研究  

MAGNETOSTRATIGRAPHY OF LATE NEOGENE RED CLAYS IN THE FUXING AREA OF WESTERN FOOTHILLS OF THE LLIANG MOUNTAINS

作　　者：徐永[1,2] 岳乐平[2] 李建星[1,2] 王建其[2] 孙勃[2] 孙蕗[2] 张佳音[2] 马冀[2] 

机构地区：[1]中国地质调查局西安地质调查中心,陕西西安710054 [2]西北大学大陆动力学国家重点实验室,陕西西安710069

出　　处：《地层学杂志》2013年第1期33-40,共8页Journal of Stratigraphy

基　　金：国家自然科学基金项目(No.41202133;41002052;41072136)资助

摘　　要：吕梁山西麓中上新世的一套厚层红黏土层记录了吕梁山前盆地的演化和吕梁山新近纪的隆升。山前不同的构造部位,各异的古地貌特征导致红黏土的堆积特征差别较大,柳林复兴地区黏土层的下部常含有数层化石层和薄厚不等的砾石层。本文对复兴地区的红黏土进行了岩石磁学和磁性地层学研究,得出了复兴地区红黏土及所含砾石层和化石层的古地磁年龄,并通过野外沉积特征以及粒度等指标探讨了复兴地区红黏土的形成过程。岩石磁学结果表明,红黏土中特征剩磁的载体为磁铁矿和赤铁矿。古地磁和生物化石显示复兴剖面的年龄为7.1～2.6Ma。其中所含厚层砾石层的古地磁年龄约为5.2Ma。两层化石层的年龄分别为～6.8Ma和～7.1Ma。剖面野外沉积特征和粒度变化显示柳林复兴地区红黏土堆积初期有水流作用的参与。Thick red clays were deposited in the western foothills of the Ltiliang Mountains, which record the evolution of the foreland basin of the Lilliang Mountains and the uplift history of the Ltiliang Mountains during the Neogene Period. In the Fuxing area of Liulin County, there are several fossil layers and gravel layers in the red clay deposits. Rock magnetism and magnetostratigraphy of red clay in Fuxing were studied. Field investigation and grain-size distribution data were used to analyze the depositional processes of the red clays. Rock magnetic results show that the magnetic carriers of characteristic remnant magnetization of the red clays are mainly magnetite and hematite. The age of the Fuxing red clays is between 7.1 and 2.6 Ma. The age of the thick gravel layer is～5.2 Ma. The ages of the two fossil layers are～6.8 Ma and ～7.1 Ma. Sedimentary structures and grain-size distribution pattern indicate that fluvial or alluvial processes participated in the early deposition of the Fuxing red clays.

关 键 词：磁性地层 红黏土 粒度 上新世 新近纪 复兴 吕梁山 山西 

分 类 号：P534.62[天文地球—古生物学与地层学]