Abstract: Some fossilized mammalian teeth and antlers collected from various stratigraphical position of primary Sjara-osso-gol sediment are dated by both 230Th and 231 Pa methods.
The results are:
1) The lower Sjara-osso-gol formation (lacustrine deposition) was accumulated between 30—50 thousand years B.P. The "Ordos man'' and "Sjara-osso-gol Culture,, are located in this formation.
2) The upper Sjara-osso-gol formation (alluvial deposition) is dated no more than 30 thousand years B.P.

Key words: Uranium series dating; Ordos man; Sjara-osso-gol Culture