蒙甘青地区白垩纪原型盆地分布特征及盆山格局

通过野外地质调查并结合前人资料,对蒙甘青地区白垩纪原型盆地沉积特征及盆山格局进行了研究。结果表明,白垩纪时期,因受北侧西伯利亚板块、东侧太平洋板块和西南印度板块共同影响,研究区由晚侏罗世的挤压和抬升作用进入松弛拉张裂陷阶段,早白垩世盆地沉降中心较侏罗纪向北迁移,发育了以坳陷和断陷为主的8个大小不一的沉积盆地群。晚白垩世本区受西南部印度板块与青藏高原碰撞对接的强烈影响,沉积盆地逐渐消失,此时沉积中心转移到祁连山东部及阿拉善一带,主要发育了2个沉积盆地群。早白垩世为本区烃源岩形成时期,研究该区白垩纪盆山构造发育及原型盆地沉积特征对寻找以白垩系为烃源岩的油气藏具有重要意义。

Distribution of Cretaceous Proto-basin and Basin-mountain Frame Work in Iner Mongolia-Gansu-Qinghai Area

Depositional setting and basin-mountain framework of Cretaceous proto-basin of Iner Mongolia-Gansu-Qinghai area is reconstructed based on field geological survey and previous works of others.During early Cretaceous,the studied area transferred from Late Jurassic compression and uplifting into tensional rifting stage with a northward shifting of depocenter as a result of joint influence of the northerly Siberia plate,the easterly Pacific plate and the southwesterly India plate.Eight sedimentary basin groups dominated by depression and fault depression process were formed.During Late Cretaceous,those basin groups died out and there are two basin groups within Iner Mongolia-Gansu-Qinghai area and depocenter shifted to the eastern part of Qilian Mountain and Alashan area due to impact of collision and combination of India plate with Tibet.The early Cretaceous is the most important period for source rock formation and in consequence,reconstruction of Cretaceous basin-mountain tectonic development and proto basin depositional setting is of great significance to the exploration of oil and gas from Cretaceous source rocks in Iner Mongolia-Gansu-Qinghai area.