【摘要】 本文通过综合研究雀莫错等三条剖面及其中丰富的古生物资料和沉积旋同、岩石组合特征等,将青海西南部唐古拉山地区的侏罗系划分为中侏罗统雀莫错组、沱沱河组、布曲组、夏里组和上侏罗统索瓦组、扎窝茸组共六个地方性地层单位,并叙述和讨论了这些地层单位(包括部分新发现地层)的沉积特征与地质时代,还简要分析了该区侏罗纪古地理环境。更多还原

【Abstract】 Marine Jurassic strata 6096 m thick are developed in the Tangula Mountains in southwestern Qinghai Province. They are characterized by a distinct sequence and abundant fossils. The strata were conventionally called by the predecessors the "Yaushiping Group" and divided into the Lower Sandstone, Lower Limestone, Upper Sandstone and Upper Limestone Formations, and their age was roughly assigned to Middle Jurassic (Bathonian Stage) or Middle—Late Jurassic. When the author conducted 1:200,000 regional geological surveys in the area in 1984—1985, he found that the top of the original Yanshiping Group was overlain by sediments of a regressive sequence yielding the elements of the Kimmeridgian—Tithonian bivalves such as Laevitrigonia gibbosa and Myopholus multicostata. The lower part of the Lower Sandstone Formation (Table 1) of the original Yanshiping Group yields the typical genera and species of Bajocian bivalves such as Kobayashites, Protocardia truncata and Pleuromya oblita, so should be assigned to the Bajocian Stage. The original Upper Limestone Formation (Table 1) is actually Oxfordian sediments. According to three measured sections at Qoima Co, Yanshiping and road squad 102 and abundant assemblages of bivalves and brachiopods combined with the lithology and features of sedimentary cycles, the Jurassic system of the area may be divided into six local stratigraphic units: the Middle Jurassic Qoima Co, Tuotuo River, Biqu and Gyari Formations and the Upper Jurassic Suowa and Zhaworong Formatious. A further study shows that two major events of transgression and regression happened during the Jurassic in the area: one in the Middle Jurassic and the other in the Late Jurassic. The sedimentary environments were mainly littoral and subordinately neritic with occasional continental sediments.更多还原