青藏高原天水盆地中新世沉积物碳氧同位素对古气候演化的指示  

THE OXYGEN AND CARBON ISOTOPIC RECORDS OF MIOCENE SEDIMENTS IN THE TIANSHUI BASIN OF THE NORTHESTERN TIBETAN PLATEAU AND THEIR PALEOCLIMATIC IMPLICATIONS

作　　者：侯战方 张军[1] 宋春晖[1] 李吉均[1,2] 刘佳[1] 刘善品[1] 惠争闯[1] 彭廷江[1] 

机构地区：[1]兰州大学西部环境教育部重点实验室,西部环境与气候变化研究院,兰州730000 [2]江苏省环境演变与生态建设重点实验室,南京师范大学地理科学学院,南京210097

出　　处：《海洋地质与第四纪地质》2011年第3期69-78,共10页Marine Geology & Quaternary Geology

基　　金：国家重点基础研究发展规划项目(2005CB422001);国家自然科学基金项目(40721061);国家创新研究群体科学基金(NSFC40721061);教育部高等学校博士学科专项科研基金(20070730025,20090211120027);中央高校基本科研业务费专项资金(lzujbky-2009-86)

摘　　要：青藏高原东北缘天水盆地位于东部季风区、西北干旱区及青藏高原区三大自然带的交汇地带,对气候变化十分敏感。根据该区下山剖面中新世沉积物碳氧同位素组成及TOC含量变化特征,揭示该区中新世气候演化经历了5个阶段:17.02～12.26Ma时期降水较多,气候相当暖湿;12.26～10.92Ma时期气候相对冷湿;10.92～8.50Ma时期降水减少,气候相对冷干;8.50～7.05Ma时期气候相对暖湿;7.05～6.05Ma时期气候相对冷干。其中12.26～10.92Ma气候相对冷湿,与全球降温有关。10.92～8.50Ma时期沉积物碳酸盐中δ18 O较10.92Ma之前偏重1.5‰,可能由于10.92Ma左右青藏高原隆升到可以改变大气环流的高度,阻遏了西南印度洋和南太平洋携带湿润气流到达或很少到达该区域。7.05Ma以来气候相对冷干,代表亚洲内陆干旱化开始形成。这些为深入理解中新世期间青藏高原隆升历史、亚洲内陆干旱化及该区域的气候演化过程具有重要意义。The Tianshui basin of the northeastern Tibetan Plateau is located in the intersection of the eastern monsoon area,the northwest arid area and the Qinghai-Tibet Plateau cold and arid regions,so it is very sensitive to climatic change.Based on the δ18O,δ13C and TOC data along the Xiashan section,this paper deals with the Miocene climatic evolution of the Tianshui basin.The climatic change in the region can be divided into five stages in 17.02~12.26 Ma,12.26~10.92 Ma,10.92~8.50 Ma,8.50~7.050 Ma,7.05~6.05 Ma respectively.During the period of 17.02~12.26 Ma,the climate was very warm and humid under high precipitation;in the interval from 12.26 to 10.92 Ma,the climate was relative cold and humid;from 10.92 to 8.50 Ma,with less precipitation,the climate was relative cold and dry;in the phase 8.50~7.05 Ma,the climate was relative warm and humid;from 7.05 to 6.05 Ma,the climate was relative cold and dry.Global cooling may be the reason for the relative cold and wet climate during 12.26~10.92 Ma.The average δ18O values during the 10.92~8.50 Ma period are 1.5‰ more positive than that of the period prior to 10.92 Ma,probably due to the elevation of the Qinghai-Tibet Plateau that was sufficient to change the atmospheric circulation,by blocking the moisture from the Indian Ocean or south Pacific into the Tianshui basin.Since 7.05 Ma,the climate has been relatively cold and dry,marking the initiation of aridification in the inland Asian.All of the information is important to the understanding of the history of up-lifting of the Tibetan Plateau in-depth,the aridification in Asia interior as well as the climatic evolution in this region.

关 键 词：碳、氧同位素 中新世 青藏高原 天水盆地 

分 类 号：P597[天文地球—地球化学]