藏南聂拉木北部喜马拉雅山主脊带侏罗系重解

通过野外调查和地层系统校正,认为前人在该区划分的侏罗纪地层系统存在偏差。下侏罗统在喜马拉雅山主脊带南北两侧岩相变化较大,普普嘎组可能穿时;中上侏罗统岩相变化较小;侏罗系总厚度不超过1400m。中侏罗统鲕粒铁质岩所对应的岩石地层单元按命名先后原则应为定结组,形成于外陆棚环境,可能与全球侏罗纪海泛时期洋流涌入有关,代表特提斯喜马拉雅地区中侏罗世晚巴通期一次沉积地质事件;晚侏罗世基末利期在特提斯喜马拉雅可能存在与欧洲同期的缺氧事件。

Reinterpretation of the Jurassic across the main Himalayan ridge north of Nyalam, southern Tibet, China

According to recent geological investigations and correction of the stratigraphic system, the authors think that there are mistakes in the previous stratigraphic division of the Jurassic in the main Himalayan ridge zone. The Lower Jurassic litho facies in both north and south sides of the Himalayas changes greatly, and the Pupuga Formation is diachronic. The Middle-Upper Jurassic lithofacies changes little. The total thickness of the Jurassic is less than 1400 m instead of over 2400 m. Following the law of priority, the Middle Jurassic oolitic ironstone should be back to the "Dingjie Formation" which was named in 1992. Oolitic ironstone may have formed in the outer continental shelf environment, which might be related to the inflow of the oceanic current during the global Jurassic marine flooding stage. It could be resulted from a sedimentary event in late Bathonian of Middle Jurassic in the Tethyan Himalaya area. A coeval anoxic event with that in Europe may have taken place in the Late Jurassic Kimmeridgian in the Tethyan Himalaya.