Abstract:The Late Triassic Nadi Kangri Formation, which delineates an E-W zoned array within northern Qiangtang basin northern Tibet, is mainly composed of lower volcaniclastic rocks with interbedded rhyolites, basalts and upper sedimentary sequences. A paleo-weathered crust is first identified at the top of the Late Triassic Xiaochaka Formation by our fieldwork in detail and petrochemical study. Combined with the different types of basal boundary and basal conglomerate observed in the bottom of the Nadi Kangri Formation, this paper confirms that a sedimentary gap was probably existed between the Nadi Kangri Formation and its underlying strata. The gap was actually observed by previous study of magnetic stratigraphy and was thought to have lasted about 2 Ma. The time span of the Xiaochaka Formation has also been constrained by related biostratum in present paper. It is inferred that the age of volcanism in the Nadi Kangri Formation is probably occurred between the Late Triassic Norian and Rhaetian, prior to the previous age-constraint of this Formation. It is proposed that the Nadi Kangri Formation volcanic rocks have potential significances in evaluating the Late Triassic biotic crisis, climate change, and regression event in the eastern Tethys.