琼州海峡第四纪层序格架及其沉积演化

Quaternary sequence framework and sedimentary evolution of Qiongzhou Straits

为探讨琼州海峡地区第四纪地层结构及其沉积演化过程,对琼州海峡1140 km高分辨率单道地震剖面和5个钻孔岩心资料进行解译,结合粒度分析、^(14)C测年、光释光测年以及微体古生物分析等测试数据,描述地震相特征及沉积环境,并进行地层划分和对比,分析沉积环境变化规律。结果表明:单道地震剖面上共识别出8个地震反射界面,划分为6套地震层序。琼州海峡第四纪沉积整体表现为“西厚东薄”,主要分布在海峡东、西口海域及海峡南北两侧边坡,海峡中部深水区几乎被强劲海流冲蚀殆尽。琼州海峡受海平面频繁升降、新构造运动及强劲水动力影响,第四纪沉积环境变化复杂:早、中更新世时期出现多次海陆交互沉积;晚更新世时期海峡西部海陆交互沉积明显,东部则以浅海沉积为主;全新世时期海侵过程中也出现数次沉积间断。

To explore the Quaternary stratigraphic structure and sedimentary evolution process in the Qiongzhou Strait area,the 1140 km high-resolution single-channel seismic profile and 5 borehole core data in the Qiongzhou Strait were interpreted,and combined with grain size analysis,^(14)C dating,optically stimulated luminescence dating and microfossil analysis,the characteristics of seismic facies and sedimentary environment were described,and stratigraphic division and correlation were carried out to analyze the variation law of sedimentary environment.The results show that a total of 8 seismic reflection interfaces have been identified on the single seismic section,which are divided into 6 sets of seismic sequences.The overall Quaternary sediment in the Qiongzhou Strait is characterized by“thick in the west and thin in the east”,mainly distributed in the eastern and western mouths of the strait and on the slopes on both sides of the strait.The deepwater area in the central part of the strait has been almost completely eroded by strong currents.Due to frequent fluctuations in sea level,neotectonic movements,and strong hydrodynamic forces,the Quaternary sedimentary environment in the Qiongzhou Strait has undergone complex changes:multiple intercontinental sedimentations occurred during the early and middle Pleistocene periods;during the late Pleistocene,there was a significant interaction between the sea and land in the western part of the strait,while shallow sea deposits dominated the eastern part;several sedimentary hiatuses also occurred during the transgression of the Holocene period.