中生代以來南方大陸和歐亞大陸之聚合研究(二)

The northeastern South China Sea (SCS) continental margin evolved from Andean-type margin in Jurassic to Western Paci?c-type margin around 90 Ma. The Dongsha Islands area experienced the complex Cenozoic tectonic interaction between SCS seafloor spreading, subduction (Manila Trench), and arc-continent collision (Taiwan). This study used recent industrial seismic profiles with better resolution and well data to interpret the seismic sequences. Focusing on Cenozoic, we delineate the seismic reflectors as T6 (23.03 Ma), SB20.43, SB17.25, SB16.18, SB14.78, T3 (13.66 Ma), SB12.76, T2 (11.79), SB9.32, and T1 (5.83 Ma). The seismic termination of significant seismic reflectors indicated two contractional events (occurred ~23 and ~9 Ma) and one uplift event (occurred ~12 Ma). The earlier contractional event (~23 Ma) may be correlated with the Baiyun movement and resulted from the transition from passive to active rifting. The later contractional event (~9 Ma) was possibly caused by obduction of northern SCS continental margin or arc-arc collision of Taiwan area. The seismic reflector SB12.76 overlain by continuous onlapping strata termination indicated an uplift event (~12 Ma), and can be correlated with the basal foreland unconformity in SW Taiwan offshore basin.