Reconstruction of the Mesozoic Prototype Basin in the West Qaidam Basin

Key words: 
• the western Qaidam basin /
• Altyn Mountain /
• Mesozoic /
• prototype basin /
• paleocurrents

Abstract: In the exploration practice, it is found that the inadequate knowledge about the Mesozoic proto-type basin in the western Qaidam basin slowed the oil and gas exploration in this area. Based on analyzing the paleocurrents, combining the Mesozoic outcrops and seismic interpretation data, the Mesozoic prototype of the western Qaidam basin is recovered in this paper. There developed an intermountain depression between the old Alabasitao mountain and the Kunlun mountain, which trending is EW. The evolution of the depression includes two stages: the EarlyMiddle Jurassic and the Late JurassicCretaceous, corresponding developed two prototype basins. The EarlyMiddle Jurassic basin is fault basin type and the Late JurassicCretaceous depression type. During the EarlyMiddle Jurassic, the Altyn Tagh was not uplifted. The deposition was coal bearing formation. The depocenter was in the present Altyn Tagh region. The northwest edge of the depression crossed the Altyn Tagh and conjoined with the Southeast Tarim basin, the northeast edge was ended in the Alabasitao region, and the south was restricted along the HongliuquanMeigouHeishishanYueyashan. During the LateCretaceous, the Altyn Tagh uplifted rapidly and became a province. The deposition was coarse clastic formation. The subsidence and sedimentation area migrated gradually towards inside basin because of the uplift of the Altyn Mountain. The south edge of the depression was along the AlaerHongliuquanHonggouziYue3jing.