东海陆架盆地丽水凹陷构造演化特征

Tectonic evolution characteristics of Lishui Sag,East China Sea Shelf Basin

为了精细刻画东海陆架盆地丽水凹陷构造演化历史,从北至南选取了丽水凹陷8条骨干地震测线剖面,运用平衡剖面技术,对其进行了构造演化剖面的恢复,测定了伸缩量、伸缩率、伸缩速率等参数,对丽水凹陷10个地质时期的伸缩特征进行了定量化、精细化研究,探讨了其阶段性、空间性伸缩特征。丽水凹陷构造演化阶划可分为断陷初期、断陷早期、断陷晚期、拗陷期、反转期和稳定沉降期6个阶段,古新统灵峰组下段沉积期(T_(9)^(0)—T_(8)^(8))是断陷作用最强烈、断层活动性最强阶段,而不同演化阶段的伸缩特征在空间上存在差异。丽水凹陷的构造演化反映了东海陆架盆地晚中生代以来从早到晚、自西向东发生构造与沉积迁移的规律,其受控于(古)太平洋板块向欧亚板块后撤式俯冲的动力学背景,并与东海陆架盆地周围各大汇聚板块的相互作用息息相关。

To detailly describe the tectonic evolution history of Lishui Sag of the East China Sea Shelf Basin,eight seismic sections from north to south were selected.The balanced section technology was used to restore structural evolution section,and some parameters such as extension amount,ratio and rate were measured.The extension characteristics of the sag during ten geological periods were described quantitatively and finely,moreover,the stage and spatial extension characteristics were also discussed.The structural evolution of the sag were classified into six stages:the initial,early and late stages of fault depression,the depression stage,the inversion stage and the stable subsidence stage.It was considered that the most intense stage for fault depression and fault activity in the sag was the deposition stage of the lower Lingfeng Formation(T_(9)^(0)-T_(8)^(8)),and the extension and contraction characteristics of different evolution stages were different in space.The tectonic evolution of the Lishui Sag,controlled by the geodynamic background of retrogressive subduction of the(paleo)Pacific plate to the Eurasian plate,reflects the rule of tectonic and sedimentary migration from west to east in the East China Sea Shelf Basin since the Late Mesozoic,and is closely related to the interaction of the convergence plates around the East China Sea shelf Basin.