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.