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We conducted an integrated palaeomagnetic and stratigraphic study on a 5452.8 m thick sedimentary sequence of the Hoh Xil Basin in northern Qinghai-Tibet Plateau to obtain a chronostratigraphic framework for these sediments. A total of 966 individual oriented palaeomagnetic samples (spaced at stratigraphic intervals) were collected from six measured sections in the Hoh Xil Basin. Maenetic directions in these samples were obtained by progressive thermal (mainly) and alternating-dield demagnetization experiments. Most samples exhibit two components of magnetization. The lower unblocking temperature component is an overprint resembling the present-day geocentric axial dipole field direction at the sampling locality. The most stable, characteristic remanencc (ChRM) appears to be an early chemical remanent magnetization on residing mainly in haematite. The positivc results of fold and reversal tests indicate that the (ChRM is a record of the palaeomagnetic field close to the time of formation of these sediments. Further evidence for the magnetization of these sediments acquired close to their time of deposition is the fact that patterns of magnetic reversals can be matched with the established polarity timescale. On the basis of the distinct interval of magnetic reversal zones and biostratigraphic datums. l3 magnetozones can be recognized at the Hoh Xil Bani, that range from Chrones C11 to C23 (30.l-5l.0 Ma). The age of the Fenghuoshan Group is palaeomagnetically dated as 51-31 Ma (Early Eocene-Middle Early Oligocene), and the age of the Yaxicuo Group is between 31 and 30 Ma (Middle Early Oligocene-Late Early Oligocene). The new palaeomagnetic data from the Fenghuoshan Group suggest that it has undergone no significant rotation since the Oligocene. In contrast, declination data from the Yaxicuo Group in Wudaoliang area imply a vertical-axis clockwise rotation (29.1 ± 8.5°) since the Late Oligocene. The Tertiary palaeomagnetic pole position of the Hoh Xi... [ABSTRACT FROM AUTHOR]