黄土高原新近纪红粘土粒度特征及环境意义  

Grain-size Characteristics and Environmental Implication of Neogene Red Clays in the Chinese Loess Plateau

作　　者：路珂珂 陈忠[1] 杨雁鹏 张佳琳 赵忠强 夏顶洪 倪春中[1] 宋垠先 张世涛[1] LU Keke;CHEN Zhong;YANG Yanpeng;ZHANG Jialin;ZHAO Zhongqiang;XIA Dinghong;NI Chunzhong;SONG Yinxian;ZHANG Shitao(Kunming University of Science and Technology,Faculty of Land Resource Engineering,Kunming 650093,China)

机构地区：[1]昆明理工大学国土资源工程学院,昆明650093

出　　处：《高校地质学报》2023年第5期713-725,共13页Geological Journal of China Universities

基　　金：国家自然科学基金项目(41561001)资助。

摘　　要：黄土高原红粘土的风成成因已得到一致的认可,目前发现最早的红粘土出现在渐新世末中新世初,表明古近纪末中国西北内陆地区干旱化环境就已形成。黄土高原红粘土的粒度特征显示自北而南平均粒径逐渐减小,表明了初始的季风系统已经建立,冬季风对风尘物质的传输具有重要作用。红粘土的粒度分布曲线显示其有两个组分组成,其中粗粒(>20μm)代表了近地面风(冬季风)传输部分,而细粒(<5μm)代表了高空西风传输部分,粒度组成特征很好地记录了大气环流的发展变化。自渐新世末,六盘山以西的红粘土显示在21.3~20.2Ma、16.0~13.3Ma和8.7~6.9Ma三个时期平均粒径增大,沉积速率升高,其可能与全球变冷和青藏高原阶段性隆升有关,其中8.7~6.9 Ma主要受全球变冷控制。而六盘山以东的红粘土剖面,粒度变化特征显示在7.6~6.2 Ma,或至5.4 Ma粒径都较粗,表明冬季风较强;之后至3.6 Ma平均粒径较细,沉积速率较低,指示了冬季风发育较弱,为气候环境较好的阶段;从3.6~2.6 Ma,大多数剖面都显示平均粒径增大,沉积速率增加,冬夏季风同时增强,进入向第四纪冰期过渡的阶段。北极冰盖的发育、青藏高原的隆升可能是产生变化的原因。The aeolian origin of red clays in the Loess Plateau has been unanimously recognized.The earliest red clay was found in the late Oligocene and early Miocene,indicating that the arid environment had been formed in the inland northwest of China at the end of Paleogene.The grain size characteristics of red clay in the loess plateau show that the average grain size gradually decreases from the north to the south,indicating that the initial monsoon system has been established,and the winter wind played an important role in the transport of aeolian dust.The grain size distribution of red clay indiactes that it is composed of two components.The coarse grain(>20μm)represents those transported by the near surface wind(winter wind),while the fine grain(<5μm)represents those transported by the upper westerly wind.The grain size composition characteristics of red clays well record the development and change of atmospheric circulation.Since the end of Oligocene,the average grain size and sedimentation rate of red clays in the west of Liupanshan Mountain increased at 21.3-20.2 Ma,16.0-13.3 Ma and 8.7-6.9 Ma,which may be related to global cooling and the Qinghai-Tibet Plateau uplift,and the 8.7-6.9 Ma increase was mainly controlled by global cooling.In the red clay section to the east of Liupanshan,the grain size of variation characteristics shows that the grains deposited during 7.6 Ma to 6.2 Ma or to 5.4 Ma is coarse,indicating that the winter monsoon was strong.After that,the average particle size was fine up to 3.6 Ma,and the deposition rate was low,indicating that the winter monsoon was weak climate environment.From 3.6 Ma to 2.6 Ma,most profiles show an increase in mean grain size,an increase in sedimentation rates,and an increase in both winter and summer monsoon,which indicates to the transition to Quaternary glacial period.The development of the Arctic ice sheet and the uplift of the Qinghai-Tibet Plateau may have contributed to these changes.

关 键 词：粒度 红粘土 黄土高原 冬季风 环境意义 

分 类 号：P594[天文地球—地球化学]