The drilling Well QZ-16,located in the eastern part of the Qiangtang Basin, first recovered a complete Upper Triassic to Lower Jurassic strata and clearly recorded the sedimentary environment transformation process in the eastern part of Qiangtang Basin during the Late Triassic to Early—Middle Jurassic Epoch.On the basis of comprehensive analysis of the core samples of the Well QZ-16 along with the data of the Well QZ-7 and the Well QZ-8 in this area,the sedimentary environment transformation characteristics of the Late Triassic to Early—Middle Jurassic transition period in the eastern part of the Qiangtang Basin are comprehensively analyzed.Methods: In this paper,field observation and indoor thin-section analysis of the core samples of the Well QZ-16 along with the Well QZ-7 and the Well QZ-8 were carried out.The trace elements of the fine clastic rock samples from the Quemo Co Formation of the Well QZ-16 in the Quemo Lake (Quemo Co) area were measured. And the zircon U-Pb age of tuff layer of the E’erlongba Formation was determined by LA-ICP-MS.Results: The Upper Triassic strata mainly consist of the Bolila Formation,Bagong Formation and E’erlongba Formation,which were deposited in restricted platform,delta and volcanic eruption environment,respectively,representing the end of the foreland basin revolution and the onset of the new Qiangtang Mesozoic Basin.The purplish-red conglomerate deposits of the Lower—Middle Jurassic Quemo Co Formation represent the initial deposition after the opening of the rift basin,which formed in fluvial environment,and then gradually transferred to the offshore lacustrine sedimentary environment with the seawater transgression from south.Overall,this period was characterized by the disappearance of the foreland basin opening of the rift basin early filling process of the rift basin.The Late Triassic marine sediments in the Qiangtang Basin gradually transformed to continental sediments during the Norian period (~220Ma),which also represented the beginning of the Qiangtang Jurassic Basin evolution history.