法尔维海盆构造特征及演化

Structural characteristics and evolution of the Fairway Basin

法尔维海盆位于西南太平洋海域豪勋爵海丘东侧、新喀里多尼亚岛西侧,是全球油气勘探的前沿地区。但目前对于该海盆的构造演化研究较为薄弱,限制了该海盆油气资源的进一步勘探开发。本文通过从新西兰塔斯曼海数据库搜集到大量地球物理资料,使用2D Move软件,通过平衡剖面技术进行构造演化模拟,结合区域动力学机制将海盆北部和南部的构造演化分为7个阶段:(1)早白垩世至晚白垩世陆内裂谷阶段;(2)晚白垩世断坳过渡阶段;(3)始新世早期坳陷阶段;(4)始新世晚期一次构造反转阶段;(5)始新世至渐新世热沉降阶段;(6)渐新世至中新世二次构造反转阶段;(7)中新世至今海洋沉降阶段。由于海盆中部未发现有明显的二次构造反转阶段,所以将海盆中部的构造演化划分为5个阶段:(1)早白垩世至晚白垩世陆内裂谷阶段;(2)晚白垩世断坳过渡阶段;(3)始新世早期坳陷阶段;(4)始新世晚期构造反转阶段;(5)中新世至今海洋沉降阶段。此阶段海盆整体下坳,逐渐形成现今样貌。法尔维海盆北部受到区域构造活动影响较大,白垩系地层发育较多的断裂构造;海盆中部晚白垩统地层发生较多的底辟构造;海盆南部从形成至今,受到构造活动影响较小,发育地层完整,前新生代地层较厚。整个法尔维海盆北部构造活动较强,中部较弱,南部较小。沉积地层从北到南由厚变薄。

The Fairway Basin is located on the eastern side of the Lord Howe Ridge in the southwestern Pacific Ocean and on the west side of the New Caledonia.It is the frontier of global oil and gas exploration.However,the current research on the tectonic evolution of the basin is still weak,which limits the further exploration and development on the oil and gas resources in the basin.A large amount of geophysical data from the Tasman Sea resource bank in the New Zealand are collected in this paper.The tectonic evolution simulation was carried out by using the 2D Move balance profile technique,and combining regional dynamics,the tectonic evolution of the northern and southern basins is divided into seven phases:(1)intracontinental rift stage from early Cretaceous to late Cretaceous;(2)late Cretaceous fault transition period;(3)the early depression stage of the Eocene;(4)a tectonic inversion stage in the late Eocene;(5)the thermal sedimentation stage from Eocene to Oligocene;(6)secondary tectonic inversion from Oligocene to Miocene;(7)ocean subsidence stage.Since no obvious secondary tectonic inversion stage was found in the central basin,the structural evolution of the central basin is divided into five stages:(1)intracontinental rift stage from early Cretaceous to late Cretaceous;(2)late Cretaceous fault transition period;(3)the early depression stage of the Eocene;(4)the tectonic inversion stage in the late Eocene;(5)the stage of marine subsidence from the Eocene to the present.At this stage,the basin as a whole descended and gradually formed its present appearance.The northern part of the Fairway Basin is greatly affected by regional tectonic activities,and the Cretaceous strata have more fault structures.More diapir structure occurred in the late Cretaceous strata in the central part of the basin.Since the formation of the southern part of the basin,it has been less affected by tectonic activities,the developmental strata are intact,and the pre-Cenozoic strata are thicker.The tectonic activity is strong in the northern part of the Fairway Basin,with a weaker central part and a smaller southern part.The sedimentary strata are thickened and thinned from north to south.