西藏西部昂拉仁错地区下白垩统岩石地层特征及空间变化规律

将西藏昂拉仁错地区下白垩统划分为则弄群、多尼组、郎山组和捷嘎组4个正式岩石地层单位。讨论了各组段的空间分布、岩石组合特征、沉积环境及横向变化规律。认为多尼组仅分布于班戈-八宿地层分区的东部,在改则厚齿玛里以西相变尖灭,与则弄群二段既有上下层位关系又呈横向相变关系。郎山组为只见于昂拉仁错北部班戈-八宿地层分区内的一套稳定碳酸盐台地相沉积,而捷嘎组为只见于昂拉仁错中南部措勤-申扎地层分区内的较活动的火山活动碳酸盐台地相沉积。郎山组与捷嘎组为同时异相关系。

Characteristics and spatial variation of the Lower Cretaceous lithostratigraphy in the Ngangla Ringco area, western Tibet, China

The Low Cretaceous in the Ngangla Ringco area is divided into four formal lithostratigraphic units; they are the Zelong Group, Duoni Formation, Langshan Formation and Jiega Formation. Their spatial distribution, lithological characteristics, sedimentary environments and lateral variation are discussed in the paper. The Duoni Formation is only distributed over the eastern part of the Bangkog-Baxoi stratigraphic area and changes facially and pinches out west of Houchimali, Garze. It possesses stratigraphic relationships and lateral facies change relationships with the Second Member of the Zelong Group. The Langshan Formation is a succession of stable carbonate platform facies sediments, only found in the Bangkog-Baxoi stratigraphic area, northern Ngangla Ringco. The Jiega Formation is marked by active carbonate platform facies sediments with volcanic activity, found only in the Coqen-Xainza stratigraphic area, south-central Ngangla Ringco. The Langshan Formation has a synchronic but heteropic relation with the Jiega Formation.