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摘要: 勘探实践表明,对柴达木盆地西部中生界原型盆地认识不够,是导致该区侏罗系油气勘探难以取得重大突破的主要原因。以古流分析为主要手段,结合地表露头及地震解释资料研究认为,中生界在古阿拉巴斯套山与古昆仑山间发育一个大的近EW向展布的内陆山间坳陷(古泛茫崖坳陷)。坳陷演化可分为早—中侏罗世和晚侏罗世—白垩纪两个阶段,分别对应发育了伸展断陷和挤压坳陷两种原型盆地类型。早、中侏罗世,阿尔金山尚未隆升,为主要沉积区。沉积环境比较动荡,沉积物以暗色含煤建造为主。沉积中心在现今的阿尔金山区,坳陷西北部边界越过阿尔金山区与塔东南地区相通;东北部边界位于阿拉巴斯套山前;南部边界在煤沟—采石岭—黑石山—月牙山一线。晚侏罗世—白垩纪,阿尔金山快速隆升为物源区,开始分割塔东南和柴达木盆地西部沉积。坳陷沉积物以干旱气候下的红色粗碎屑岩建造为主,沉积、沉降中心由阿尔金山区向盆地内部发生迁移,南部边界已迁移至阿拉尔—红柳泉—红沟子—月3井一带。该研究对柴达木盆地资源潜力评价及勘探部署具有重要意义。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 prototype 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 EW. The evolution of the depression includes two stages: the EarlyMiddle Jurassic and the Late JurassicCretaceous, corresponding developed two prototype basins. The EarlyMiddle Jurassic basin is fault basin type and the Late JurassicCretaceous depression type. During the EarlyMiddle 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 HongliuquanMeigouHeishishanYueyashan. During the LateCretaceous, 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 AlaerHongliuquanHonggouziYue3jing.
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Key words:
- the western Qaidam basin /
- Altyn Mountain /
- Mesozoic /
- prototype basin /
- paleocurrents
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