六盘山天池湖泊岩芯的磁学特征及所指示的环境意义.docVIP

 六盘山天池湖泊岩芯的磁学特征及所指示 的环境意义# 张欣佳，周爱锋** 5 10 15 （兰州大学西部环境教育部重点实验室，兰州 750000） 摘要：本文对六盘山天池长 11m 的 GSA 孔湖泊沉积岩芯样品进行了磁化率、非磁滞剩磁、 等温剩磁测试。结果表明 GSA 孔岩芯磁性矿物主要是亚铁磁性及反铁磁性矿物。六盘山天 池湖泊沉积物的磁性参数变化主要受控于两种模式：整体而言，高（低）粉尘输入指示了夏 季风弱（强），成壤作用强（弱）指示夏季风强（弱）。质量磁化率 χ 等参数清晰地记录了 6200 年来六盘山天池地区的气候变化历史。可以分为 6200-1300Cal yr BP、1300Cal yr BP- 现在两个阶段。6200 年来的六盘山天池湖泊沉积物磁学数据在千年时间尺度上基本与东部 季风区变化趋势相似。但是在百年时间尺度上有着较大的差异，这是由于六盘山天池地区的 气候变化不仅仅受控于夏季风，同时还受到人类活动导致的黄土高原植被覆盖变化、冬季风 变化等因素的影响。 关键词：气候变化；六盘山天池；磁学参数；夏季风；黄土高原植被覆盖 中图分类号：P92 文献标识码: A Past environment changes recorded by magnetic characteristics of sediments from Liupan mountain Tianchi 20 25 30 35 40 Lake ZHANG Xinjia, ZHOU Aifeng (MOE Key Laboratory of West Chinas Environmental System, LanZhou 750000) Abstract: In this paper we studied the core GSA (11m) which from Liupan mountain Tianchi Lake by magnetic susceptibility,anhysteretic remanent magnetisation,isothermal remanent magnetization.The result shows there are two kinds of magnetic minerals in the GSA: ferrimagnetic and anti-ferromagnetism. The changes of magnetic data of Liupan mountain Tianchi Lake sediments were controled by two patterns: high (low) dust input shows weak (strong) summer monsoon,strong (weak) soil development shows strong (weak) summer monsoon. Magnetic susceptibility χ recorded the climate change history of study area. It can be divide into two parts: 6200-1300Cal yr BP,1300Cal yr BP-now. The climate changes in the past 6200 years in study aera were similar to the monsoon area in millennial time scales. But were much different in century time scales, the reason is that the climate of study area was not only controled by sunner monsoon,but also have other factors, such as human activity which lead to Loess Plateau Vegetation changes, and winter monsoon. Keywords: climate change; Liupan mountain Llake; magnetic parameter; summer monsoon; Loess Plateau Vegetation 0 引言 在过去 6000 年中，全球气候发生了与全新世早期明显不同的变化。有关研究认为过去 6000 年里地球轨道参数在千年尺度上的变化导致太阳能重新分配，从而使得北半球夏季赤 道辐合带南移。这一变化伴随着亚非地区季风系统的减弱