| 摘要: |
| 云南丽江地区宝相寺组(E2b)下部(原美乐组)一直被认为是水成沉积,本文认为其属于风成沉积。宝相寺组下部巨厚砂岩的主体岩性为紫红色中细粒石英砂岩,不含泥质和云母等悬移质,大型高角度平板状交错层理发育,厚度巨大,风成沙丘前积层特征明显。石英砂的磨圆度高,在电子显微镜下普遍可见风成砂所特有的碟形撞击坑、新月型撞击坑及毛玻璃化表面等特征,可能为沙漠风成沙丘沉积。研究区古近纪以来的沉积特征表明,青藏高原东部的气候经历了一个由干旱到潮湿的重大转变。推测这种气候转变可能是始新世、渐新世之交全球变冷变干事件(EOGM)在青藏高原东部的沉积响应,也可能与青藏高原初次快速隆升及东亚古季风的开始形成有关。 |
| 关键词: 始新世末 宝相寺组 风成沙丘 EOGM 古季风 |
| DOI： |
| 附件 |
| 投稿时间：2010-10-14修订日期：2011-01-06 |
| 基金项目:国家自然科学基金项目(批准号:49572113);青藏高原基础地质综合研究项目(编号:1212010610101) |
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| Discovery and significance of the Palaeogene eolian deposits in Lijiang, Yunnan |
| WU Hao, CUI Xiao-zhuang, XIONG Guo-qing, ZHANG Yu-jie, JIANG Xin-sheng |
(1. Chengdu Institute of Geology and Mineral Resources, Chengdu 610081, Sichuan, China;
2. Chinese Academy of Geological Sciences, Beijing 100037, China) |
| Abstract: |
| The lower part (formerly Meile Formation) of the Baoxiangsi Formation (E2b) in Lijiang, Yunnan has long been interpreted as the hydrogenic deposits. The integration of lithology, sedimentary textures and structures in this study indicates that the tremendous sandstones in the lower part of the Baoxiangsi Formation consist of purplish red, well-sorted and rounded medium-to fine-grained quartz sandstone characterized by large-scale high-angular tabular cross-bedding and foreset bedding of the eolian dunes. The characteristic features of dish-shaped, crescent-type impact craters and frosted surface under an electronic microscope demonstrate that the lower part of the Baoxiangsi Formation may be assigned to the eolian dune deposits deposited in desert environments. The sedimentary characteristics also show that there were gradations from dry to humid climates in eastern Qinghai-Xizang plateau. It is inferred that this climatic change may be the sedimentary responses to the Eocene-Oliocene global cooling-drying events, the rapid uplift of the plateau and formation of the palaeomonsoon in East Asia. |
| Key words: latest Eocene Baoxiangsi Formation eolian dune EOGM ancient monsoon |
