青藏高原羌塘盆地早侏罗世晚期海螂蛤页岩及其年代地层学意义  

Late Early Jurassic Posidonia shale facies in Qiangtang Basin and its chronostratigraphic significance

作　　者：苏新[1] 阴家润[1] 祝有海[2] 王平康[2] 庞守吉[2] 程宝龙[1] 张明伟[1] 张帅[2] 

机构地区：[1]中国地质大学(北京),北京100083 [2]中国地质调查局油气资源调查中心,北京100029

出　　处：《地质通报》2015年第9期1617-1628,共12页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:GZHL20110308;GZH201400301);国家重点基础发展研究规划项目(编号:2012CB822001)

摘　　要：发现于德国南部的早侏罗世土亚辛期的海螂蛤页岩相沉积是中生代最早一次,也是唯一保存在大陆地层中的全球性大洋缺氧事件的典型代表。近年中国羌塘盆地已相继发现4处海螂蛤页岩相地层。北羌塘天然气水合物钻探试验井QK-5井钻遇含海螂蛤页岩相特有化石组合的地层,厚度逾150m,是迄今所知羌塘盆地纬度最高的海螂蛤页岩相产地,其他3处分布在羌塘盆地中间隆起带以南的双湖和色哇等地。海螂蛤页岩相的分布纵贯南、北羌塘,意味着羌塘盆地在早侏罗世并没有受到中间隆起带的制约而分成南、北2个独立的沉积凹陷。北羌塘西部白龙冰河、半岛湖一带与东部雀莫措、雁石坪一带的早侏罗世沉积相截然不同,形成早侏罗世西海东陆的沉积格局。海螂蛤页岩相在羌塘盆地的发现,有助于进一步认识中生代羌塘盆地沉积和古海洋演化历史。该区以海螂蛤黑色页岩为代表的富碳沉积无论是分布面积还是沉积厚度都十分可观,对盆地的天然气水合物、页岩气及常规油气勘探具有重要的意义。Among the Mesozoic global oceanic anoxic events, the Posidonienschiefer （Posidonia shale） facies in southern Germany represents the earliest one, which is well-known all over the world. Up till now, the Posidonia shale facies has been found at 4 localities in the Qiangtang Basin, including drill holes and outcrops. In Qiangtang Gas Hydrate Scientific Well QK-5, a more than 150m black shale sediment sequence was discovered, which yielded the Early Jurassic Cleviceras elegans-Bositra buchii assemblage. The locality of Posidonia shale facies in Well QK-5 is the northernmost one, on the northern side of the ＂middle uplift zone＂ of the Qiangtang Basin, while the other three are spread in areas from Shuanghu to Sewa, on the southern side of the ＂uplift zone＂ of the basin. Actually, there is few evidence to indicate that the basin had ever been separated by a uplift during Early Jurassic. In addition, the Bailongbinghe Formation （Sowa Formation） in northeast Qiangtang, formerly thought of belonging to the Late Jurassic age, is proved to range from Early to Middle Jurassic by the Toarcian and Early Callovian ammonite successions. The discovery of Posidonia shale facies in the Qiangtang Basin is helpful to further understanding the Mesozoic sedimentary and evolution history of the basin. Considerable stratigraphic thickness and distribution area of the carbon-rich Posidonia shales in the basin would provide a very optimistic outlook for shale gas exploration.

关 键 词：海螂蛤页岩相 黑色页岩 天然气水合物 科学钻井 早侏罗世 羌塘盆地 缺氧沉积 

分 类 号：P534.52[天文地球—古生物学与地层学]