准南前陆盆地燕山期构造活动及其成藏意义

准南前陆盆地燕山期盆地格局的演变、沉积中心有规律的迁移、沉积特征(与构造活动相关的砾岩及其分布)显示晚侏罗世—早白垩世早期、晚白垩世是准南前陆盆地燕山期构造活动相对活跃的时期。晚侏罗世—早白垩世早期的喀拉扎砾岩、白垩系清水河组底砾岩为一套形成于邻近高地附近的剥蚀产物或冲积产物,其分布特征及成因是晚侏罗世—早白垩世早期局部挤压和构造隆升较为活跃的产物,也是盆地边界萎缩、盆山格局发生变化的重要证据,同时天山明显隆升并导致天山南北早白垩世沉积环境的巨大差异。准南前陆盆地烃源岩大量生排烃、圈闭形成、油气运聚成藏与燕山期构造活动关系密切;燕山期发育的储层是准南前陆盆地的主要油气储层,晚侏罗世—早白垩世早期砂砾岩和不整合分布也在一定程度上控制了油气分布,是今后寻找有利隐蔽油气藏、岩性地层油气藏的重要目标之一;燕山期古构造及其形成时间与油气成藏期的良好匹配决定其油气成藏的有效性。

The tectonism during Yanshan Period in southern Junggar foreland basin and its implications for hydrocarbon accumulation

The change of basin system,migration of depocenters,distribution of conglomerates related to tectonism of Yanshan Period were consistent with the Late Jurassic-the Earliest Cretaceous and the Late Cretaceous,implying a temporal link between sedimentation of southern Junggar foreland basin and deformation of Tianshan area.The Kalazha conglomerate and the bottom conglomerate of Cretaceous Qingshuihe Formation forming in the Late Jurassic to the earliest Cretaceous were the denudation products or alluvial conglomerates around adjacent relative highland.The distribution of these conglomerates proved that the basin boundary shrank northward obviously during the Late Jurassic to the earliest Cretaceous,and the Bogeda Mountain became another provenance of southern Junggar basin during Cretaceous.The conglomerates in southern Junggar basin recorded active tectonism and obvious uplift and denudation of Tianshan belt during the Late Jurassic-the Earliest Cretaceous and the Late Cretaceous,led to the widely different sedimentary successions in Tarim basin and southern Junggar basin.Multi-source,multi-phase hydrocarbon generation and multi-phase pool forming restricted the critical moments of the petroleum system in southern Junggar foreland basin.The Yanshan Period(Jurassic-Cretaceous) was coeval with hydrocarbon generating,migrating and accumulating in the southern Junggar foreland basin.The reservoirs of Jurassic-Cretaceous were the major hydrocarbon reservoirs,the conglomerates and unconformity also led to the formation of some hydrocarbon pools,which become the advantageous targets for future exploration of subtle pools and stratigraphic/ lithologic traps.The structures formed during Yanshan Period and before were well matched with the hydrocarbon accumulation and advantageous for petroleum exploration.