Abstract: Seinites, tsunamites and background deposits occur in the Upper Triassic Bolila Formation in Nanyaxiang Mashuangbu, Biru County, North Tibet. They are composed of three distinct sedimentary sequences: A-B-C, A-C and B-C, representing an event sedimentary sequence of earthquake-tsunami-background deposits, earthquake and background deposits(no tsunami occurring) and tsunami-background deposits(far from the center of earthquake) respectively. Earthquake event deposits in the Bolila Formation are not only the auspice of the further extension, splitting and separation of the Tethyan ocean, but also sedimentary response to the Laurasia land-Cathaysia splitting.

Key words: Biru County, northern Tibet, seismites, tsunamites, Tethyan Ocean, Bolila Formation