滇西昌宁—孟连带南段组沉积特征及成因分析  

THE SEDIMENTARY ENVIRONMENT AND ORIGIN ANALYSIS OF NANDUAN FORMATION IN CHANGNING—MENGLIAN BELT,WESTERN YUNNAN, CHINA

作　　者：崔春龙[1] 曾允孚[2] 黄志勋[2] 段丽兰[2] 

机构地区：[1]西南工学院 [2]成都理工学院

出　　处：《地质科学》1999年第1期40-48,共9页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家八五攻关项目

摘　　要：南段组是一套厚度巨大的砂岩与泥岩的互层沉积，沉积构造主要是块状层理、水平层理和少量的小型滑动变形构造、小型斜层理和粒序层理以及浪成波痕。砂岩粒度概率累积曲线显示牵引流与重力流的过渡特征，砂岩的Ｃ－Ｍ图显示重力流沉积特征。砂岩成分成熟度高（石英＞９０％），结构成熟度中等（杂质为０—１６％），有时出现沉积石英岩。砂岩和泥岩的地球化学特征表明是被动大陆边缘背景下的沉积。在南段组中新发现的Ｃｈｏｎｄｒｉｔｅｓｓｐ．，Ｓｃａｌａｒｉｔｕｂａｓｐ．，Ｐｈａｎｏｌｉｔｅｓｓｐ．３种遗迹化石和一些原地埋藏的浅海底栖双壳类化石等，则代表了一个深陆棚沉积环境。以上特征表明南段组是一套浪控三角洲前缘斜坡－深陆棚环境的近源片泛性（非扇模式）重力流和正常陆棚的复合沉积。Nanduan formation were studied in 1983,but now there are some arguements about its sedimentary environment and origin.Yunnan Regional Geology Surveying Team considered that nanduan formation is a set of abyss subadyss turbidit of the rift belt.Luo Junlie(1990)and Wang Zuguan(1991)proposed that Nanduan formation is a set of shore shallow sea deposit.Liu Benpei(1993) thought that Nanduan formation is a set of flyschoid deposit or non normal turbidit from slope to basin margin. Nanduan formation is a set of vast thickness,sandstone/mudstone interbedding deposit,in which the sandstone is principal,and its thickness is about 5000M.The thickness of the single bed sandstone is several centimeter to 10m.The characteristics of sandstone/mudstone interbedding is (1)thickness sandstone interbedded with thin mudstone;(2)thickness mudsone interbedded with thin sandstone;(3)interbedding of thin sandstone and thin mudstone,intercalated rarely by lens sandstone body.Te feature of the section texture is mainly that there is not graded bedding in single bed sandstone, the top surface of the sandstone is plane,and has a break contact with the above mudstone, and there is a weak erode surface in the top surface of the mudstone (but not groove cast or flute cast), mudstone appears slightly horizontal bedding.The sedimentary structure of the set rock is mainly massive bedding、horizontal bedding and rare small type slump structure and diagonal bedding、graded bedding and rarely wave ripple. The compositional maturity of the sandstone is higher(Q>90%), but texture maturity is intermediate (matrix 0—16%). Some sandstone, with siliceous cement and poor matrix, is sedimentary quartzite.The grain size cumulative probability curves of the sandstone show transitional depositional characteristics of gravity flow and traction current,and the C-M plot appears gravity flow sedimentary characteristic.The feature of the mineral composition,ordinary elements,trace elements(Cr: 68—224 μg/g(the same below),Ni: 13—62.93,Co: 1.4—7.8

关 键 词：沉积特征 成因分析 南段组 滇西 沉积构造 

分 类 号：P512.2[天文地球—地质学]