1.5 Ma以来黄土高原风尘堆积的岩石磁学记录与中更新世气候转型  

ROCK MAGNETIC EVIDENCES OF MIDDLE PLEISTOCENE CLIMATE TRANSITION RECORDED IN CHINESE LOESS-PALEOSOL SEQUENCE

作　　者：宋友桂[1] 方小敏[2] 石川尚人[3] 鸟居雅之[4] 李吉均[2] 史正涛[1] 强小科[1] 符超峰[1] 

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,西安710075 [2]兰州大学教育部西部环境重点实验室,兰州730000 [3]京都大学综合人间学部 [4]冈山理科大学情报学院

出　　处：《海洋地质与第四纪地质》2005年第3期43-51,共9页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目(40202019;40121303);国家重点基础研究发展规划项目(G1998040800;2004CB720202)

摘　　要：通过对黄土高原中部朝那剖面黄土-古土壤序列系统的岩石磁学分析,建立了1.5 Ma以来黄土高原高分辨率岩石磁学指标演化序列.岩石磁学记录表明本区1.5 Ma以来以0.93和0.62 Ma为界经历了3个不同的气候演化阶段.在1.5～0.93和0.62～0 Ma期间各种磁学参数大致呈同步变化趋势,能较好地与深海氧同位素(MIS)曲线相对应,而在0.93～0.62 Ma期间(相当于L9底到L6顶,MIS24-MIS16),尽管磁化率、饱和剩磁强度(Mr)、饱和磁化强度(Ms)与剩磁矫顽力(Bcr)、矫顽力(Bc)曲线的峰谷能与MIS的峰谷相对比,但该阶段的磁学参数变化幅度和形式明显不同于1.5～0.93和0.62 Ma以来的两个演化阶段.磁化率、Mr和Ms在0.93 Ma突然降低,此后变幅很小,反映夏季风较弱且相对稳定,一直维持到0.62 Ma前后.在0.9 Ma前后Bc、Bcr突然增大,可能反映了冬季风突然增强,然后宽幅波动下降.这种变化可能是黄土高原风尘堆积对中更新世气候转型事件的响应.黄土高原岩石磁学记录的中更新世气候转型事件发生于0.93 Ma,结束于0.62 Ma.造成这次气候转型事件的原因除了与全球冰量和太阳辐射变化有关之外,还可能与中更新世青藏高原急剧隆升而激发的亚洲内陆干旱化加剧,从而导致亚洲内陆沙漠的形成与扩张有关.Based on detailed rock magnetic analyses of loess-paleosol sequence at Chaona section in the central Loess Plateau, a high-resolution environmental magnetic framework has been built up for last 1.5 Ma. The changes of rock magnetic parameters indicate three major stages with 0.93 and 0.62 Ma as the boundaries, which may imply three different climate change phases. These parameters during 1.5 -0.93 and 0.62-0 Ma mostly changed synchronously, and also were well correlated to those of marine oxygen iso- tope stages （MIS）. Although the peaks of magnetic parameters curves are roughly corresponding to those of MIS from 0.93 to 0.62 Ma, the amplitude and models of parameter changes are different from the other two periods. Susceptibility, saturation remanent intensity （Mr） and saturation magnetization intensity （Ms） decreased abruptly around 0.93 Ma, and then reduced slowly until 0.62 Ma, which indicates a weak and stable summer monsoon period, while coercivity of remanence （Bcr） and Coercive fore （Bc） increased quickly around 0.9 Ma and then slowed down, implying winter monsoon enhanced around 0.9 Ma and descended slowly until 0.6 Ma. These changes from 0.93 to 0.62 Ma recorded in eolian loess-paleosol sequences possibly respond to the world-wide middle Pleistocene climatic transition event. This transition event may be related to the aggragation of drought and the forming and expanding of desert in Asian interior triggered by the accelerated uplift of the Tibetan plateau besides global ice volume and solar insolation.

关 键 词：岩石磁学 黄土-古土壤 古气候 中更新世气候转型 黄土高原 

分 类 号：P532[天文地球—古生物学与地层学]