胶莱盆地白垩纪构造演化

胶莱盆地是位于胶东半岛的白垩纪盆地,前人对该盆地的沉积?构造演化进行了相关研究,也取得了重要进展。但是关于盆地初始形成阶段古构造应力场状态还存在一些争论。本文通过对盆地内部断层滑动矢量数据的反演及节理、同沉积断层指示意义分析,将胶莱盆地白垩纪构造演化划分为五个阶段:早白垩世早期NWW-SEE向伸展,控制了莱阳群初始沉积;莱阳群沉积末期近E-W向挤压;早白垩世晚期E-W向伸展,形成了青山群;早白垩世末期NW-SE向挤压;晚白垩世近N-S向至NNE-SSW向伸展,形成了王氏群。大量的野外现象与前人研究成果均与本文得到的盆地初始成盆阶段NWW-SEE向伸展应力场相吻合。NWW-SEE向伸展作用可能是在古太平洋板块向欧亚板块俯冲过程中,古太平洋板块后撤与苏鲁造山带后造山作用的共同作用下发生的,代表胶莱盆地形成初期,受苏鲁造山带造山后期作用的影响;而青山期伸展方向的变化可能指示盆地主要受到古太平洋板块后撤的影响。盆地在白垩纪古构造应力场的作用下,分别受到早白垩世裂谷作用与晚白垩世走滑拉分作用控制,两种作用的叠加使胶莱盆地成为一个复合型盆地。

Cretaceous Tectonic Evolution of the Jiaolai Basin,North China

The Jiaolai Basin is a Cretaceous basin located in the Jiaodong Peninsula.Many important progresses concerning the sedimentary-tectonic evolution of the basin have been achieved,however,the paleotectonic stress field in the initial stage of the basin is still unclear.Based on the inversion of fault-slip data and analysis of conjugate shear joints and synsedimentary faults in the basin,we divide the Cretaceous tectonic evolution of the Jiaolai Basin into five stages according to the paleotectonic stress field:1)NWW-SEE extension in the early Early Cretaceous,which controlled the initial deposition of the Laiyang Group;2)near E-W slight compression in the late sedimentary period of the Laiyang Group;3)E-W extension in the late Early Cretaceous;4)NW-SE compression in the late Early Cretaceous,and 5)the extensional stress field between N-S to NNE-SSW in the Late Cretaceous under which the Wangshi Group were deposited.Abundant field geological phenomena and previous research results demonstrated that the NWW-SEE extensional stress field was prevalent in the initial stage of the basin.The NWW-SEE extension may ascribe to both roll-back of the Paleo-Pacific and post-orogeny of the Sulu orogenic belt.However,the change of extension direction during sedimentation of the Qingshan Group may indicate that the basin was mainly affected by the roll-back of the Paleo-Pacific.On the basis of the Cretaceous paleotectonic stress field analysis,we argue that the basin is a composite basin controlled by two processes,i.e.,the Early Cretaceous rifting and the Late Cretaceous strike-slip pull-apart,respectively.