东海西湖凹陷和钓北凹陷伸缩率及构造演化

EXTENSIONAL AND COMPRESSIVE RATIOS AND TECTONIC EVOLUTION OF THE XIHU AND DIAOBEI SAGS

东海陆架盆地位于欧亚板块的东南边缘，具有东西分带、南北分块的格局，其中东部坳陷带包括福江凹陷、西湖凹陷和钓北凹陷。选择西湖凹陷11条、钓北凹陷2条地震剖面，采用平衡剖面技术，计算了西湖凹陷和钓北凹陷新生代不同演化阶段的伸缩率。伸缩率的分析表明，T50-T34西湖凹陷和钓北凹陷处于伸展状态，T34-T12西湖凹陷处于压缩状态，T34-T30、T30-T12钓北凹陷分别处于压缩、伸展状态，T12至今西湖凹陷和钓北凹陷区域沉降。始新世中期西湖凹陷进入挤压期，玉泉运动（T30）、花港运动（T20）和龙井运动（T12）3次挤压的强度不断加剧。结合盆地充填结构分析，钓北凹陷新生代经历了早中始新世地堑式断陷、晚始新世和渐新世坳陷、早中中新世断陷和晚中新世至今整体沉降的4个演化阶段；西湖凹陷新生代经历了古新世和早中始新世断陷、晚始新世和渐新世坳陷、早中中新世反转和晚中新世至今整体沉降的4个演化阶段。西湖凹陷和钓北凹陷构造演化有很大不同，这是东海陆架盆地南北分块的重要依据。

The East China Sea Shelf Basin lies in the southeast margin of the Eurasian Plate. It is characterized by the feature of east-west zonation and north-south blocking. The east belt of the depression includes the Fujiang Sag, Diaobei Sag and Xihu Sag. This paper selected 11 balanced cross-sections from the Xihu Sag and 2 from the Diaobei Sag. The extensional and compressive ratios of the Xihu and Diaobei sags in Cenozoic were calculated by using the technique of balanced cross sections. The results showed that＇both the Xihu and Diaobei Sags were in a stretched state in T50-T34. However, they were different in other stages, for instance, the Xihu Sag was in a compressed state in T34-T12, while the Diaobei Sag in a compressed state in T34-T30and in a stretched state in T30-T12. Both of them started subsiding since T12. The Xihu Sag had remained in compress since middle Eocene. The three tectonic movements.. Yuquan （T30）, Huagang （T20） and Longjing （T12）, intensified the compression. Together with the history of basin filling, the Diaobei Sag could be divided into four evolutionary stages since Eocene： early-middle Eocene graben-type rifting, late Eocene and Oligocene depression, early-middle Miocene rifting and subsidence since late Miocene. Similarly, The Xihu Sag has also experienced four stages of evolution since Paleocene： Paleocene and early middle Eocene rifting, late Eocene and Oligocene depression, early-middle Miocene reversion and subsidence since late Miocene. The Xihu and Diaobei sags are very different in terms of tectonic evolution that is the reason of the north-south zonation in the East China Sea Shelf Basin.