三门峡会兴沟剖面黄土—古土壤序列的岩石磁学研究  

Rock Magnetism Study on Loess-Paleosol Sequence at Huixinggou Section of Sanmenxia Basin

作　　者：李兴文[1,2] 张鹏[1] 强小科[1] 敖红[1] Li Xingwen Zhang Peng Qiang Xiaoke Ao Hong(State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi＇ an 710061, China University of Chinese Academy of Sciences, Belting 100049, China)

机构地区：[1]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,陕西西安710061 [2]中国科学院大学,北京100049

出　　处：《地球科学进展》2017年第5期513-523,共11页Advances in Earth Science

基　　金：国家自然科学基金项目"中国黄土记录的布容正极性时极性漂移事件研究"(编号:41572164);黄土与第四纪地质国家重点实验室开放基金课题"汾渭地堑早期人类扩散;迁徙与融合证据"(编号:SKLLQG1502)资助~~

摘　　要：岩石磁学是古地磁学和环境磁学研究的基础,是鉴定岩石和沉积物中磁性矿物种类、粒度和含量的有效途径。对黄土高原东南部三门峡盆地的水沟—会兴沟旧石器遗址会兴沟剖面黄土—古土壤序列(S_0~S_8)进行系统的岩石磁学研究表明:本剖面沉积物的主要载磁矿物为磁铁矿、磁赤铁矿和赤铁矿,显示准单畴(PSD)磁性颗粒特征。所有磁学参数曲线均表现出基本一致的变化特征,与深海氧同位素曲线能够很好的对应,反映了第四纪以来的冰期—间冰期旋回中,东亚季风影响下的风尘黄土堆积中磁性矿物种类、粒度和含量的周期性变化特征。黄土中高矫顽力磁性矿物的相对含量要高于古土壤中的,而随着成土作用的加强,在古土壤中细粒的低矫顽力磁性矿物显著增加的同时,其中高矫顽力磁性矿物的绝对含量也相应增加。质量磁化率(χ)与非磁滞剩磁磁化率(χ_(ARM))和饱和等温剩磁(SIRM)及磁粒度参数χ_(ARM)/SIRM和χ_(ARM)/χ均呈明显的正相关关系,表明由成土作用产生的单畴(SD)颗粒和较小PSD颗粒对磁化率增强有显著的贡献。Rock magnetism is the foundation of paleomagnetism and environmental magnetism study, and is effective in identifying the components, grain size and content of magnetic minerals in rocks and sediments. A systematic rock magnetism investigation has been conducted on the Huixinggou loess-paleosol sequence at Shuigou-Huixinggou Paleolithic site of Sanmenxia Basin in the southeastern Loess Plateau. Results show that the magnetic assemblage of the section is dominated by magnetite and maghemite, as well as hematite, exhibiting the average grain size of magnetic minerals is attributed to Pseudo-Single Domain （PSD）. The variation curves of magnetic parameters are consistent and well comparable to marine oxygen isotope curves, with low values corresponding to the loess deposition during glacial periods, and high values corresponding to the paleosol development during interglacial periods, jointly demonstrating the glacial-interglacial cyclicities of magnetic mineral types, composition, and grain size of Chinese loess-paleosol sequences under the influence of alternating strengthening and weakening of Eastern Asian paleomonsoon over the Quaternary period. Comprehensive analysis reveals that the relative content of high-coercivity antiferromagnetic minerals is higher in loess than in paleosol, whilst the absolute content of high-coercivity antiferromagnetic minerals in paleosol is generally higher than that in loess accompanying increasing intensity of pedogenesis. The mass-specific magnetic susceptibility （χ） shows distinctly positive correlations with anhysteretic susceptibility （χARM）, Saturation Isothermal Remanent Magnetization （SIRM） and magnetic grain size dependent parameters （χARM/SIRM and χARM/χ）, indicating that the pedogenic producing Single Domain （SD） and small PSD ferrimagnetic particles contribute significantly to the magnetic susceptibility enhancement.

关 键 词：水沟-会兴沟旧石器遗址 黄土-古土壤序列 岩石磁学 磁学参数 古气候变化 

分 类 号：P318.4[天文地球—固体地球物理学]