PALEOZOIC STRUCTURES AND OIL-EXPLORATION PROSPECTS IN THE EASTERN TARIM BASIN, NW CHINA

The Tabei Uplift in the northern Tarim Basin, the Tadong Depression in the eastern Tarim Basin, and the Tarim Central Uplift were formed as a result of mantle diapirism. Four stages in the geological developmen t of this area can be recognized: an initial ''embryonic'' stage in th e late Proterozoic; a ''formational'' stage in the Sinian; a ''develop mental'' stage in the Early to mid-Palaezoic; and a ''completion'' sta ge in the late Palaeozoic. With long-term Palaeozoic subsidence and we ll-developed marine source rocks, the Tadong area is thought to be a p romising source region for hydrocarbons. The Tabei and Central Uplifts , located respectively north and south of the Tadong Depression, are a ncient, well-preserved structures in which hydrocarbons may have accum ulated, and could therefore constitute prospective areas for the locat ion of ''giant'' oil- and gasfields in Palaeozoic sequences. Palaeozoi c oil prospects have been confirmed in the Tabei area by the highly-pr oductive Sachan 2 well. It is expected that intensified exploration wi ll result in the location of both oil- and gasfields in the Central Up lift.