西藏南羌塘坳陷色哇地区中—下侏罗统深色岩系地层的重新厘定

Redefinition of the Mid-Lower Jurassic dark-colored rock series in the Sêwa area, southern Qiangtang, Tibet, China

针对南羌塘多玛地层分区中—下侏罗统深色岩系地层划分的混乱状况,2005年在进行羌塘盆地石油地质调查中实测了色哇地区松可尔剖面,并系统采集到大量有时代意义的菊石化石。依据化石鉴定成果,结合沉积充填序列、沉积相及层序地层分析,对该套深色岩系地层进行了重新清理,把剖面中下部黑色、深灰色泥页岩夹灰岩和中部深灰色灰岩、泥灰岩夹泥岩地层厘定为下侏罗统曲色组,上部灰色、深灰色粉砂质泥页岩厘定为中侏罗统色哇组。该剖面大量菊石的获取和地层的重新厘定,一方面丰富了本区古生物学的内容,另一方面对该区地层的划分与对比、古地理演化研究等都具有重要的科学意义。

Because of the chaotic stratigraphic division of the Mid-Lower Jurassic dark-colored rock series in the Doima stratigraphic area, southern Qiangtang, the authors measured the Songke＇er section in Sewa during the petroleum geological survey in 2005 and systematically collected abundant ammonoid fossils with chronological significance. Based on the identification of ammonoid fossils, combined with the sedimentary filling sequence, sedimentary facies and sequence stratigraphy, the dark-colored rock series is redefined. The black and dark gray mudstone-shale with limestone in the middle and lower parts of the section and dark gray limestone and marlstone with mudstone are defined as the Lower Jurassic Quse Formation, while gray and dark gray silty mudstone-shale in the upper part of section is defined as the Middle Jurassic Sewa Formation. The collection of abundant ammonoid fossils and redefinition of the strata in the section not only enrich the content of paleontology in the area, but also have great scientific significance for the stradgraphic division and correlation of the Jurassic and study of the paleogeographic evolution in the study area.