南海中生代三期海盆及其与特提斯和古太平洋的关系

THREE MESOZOIC SEA BASINS IN EASTERN AND SOUTHERN SOUTH CHINA SEA AND THEIR RELATION TO TETHYS AND PALEO-PACIFIC DOMAINS

在近年来对南海及其围区的中生代岩性、岩相古地理资料的系统搜集、整理和编图的基础上,着重分析了中生代海相地层的时空变化,进行了大区域的对比。结果表明,南海及其围区在中生代位于中特提斯的东延与古太平洋的过渡带上,发育过T1—T2、T3—J1、J3—K1 3 个时期的海盆;自中三叠世以来构造古地理演化存在明显的东西差异。T1—T2期海盆代表了古特提斯东延的萎缩阶段;T3—J1 期海盆主要受古太平洋俯冲过程的影响,但在J1 高海平面时期有中特提斯海水大量贯入;J3—K1期海盆受中特提斯的东延与古太平洋的复合影响。南海海域位于后两期海盆的边缘,经历过多期海进海退旋回,而且有上覆新生界的叠加,存在有利的油气地质条件。

Based on the data collection and map compilation for Mesozoic lithofacies and paleo-geography in the South China Sea and adjacent areas, the paper analyzes the spatial and temporal variation and regional correlation of Mesozoic marine strata. An EW differentiation in the tectonic and paleo-geographic evolution started in Middle Triassic, and sea basins existed in the eastern and southern South China Sea and adjacent areas in three periods during the Mesozoic era. Among these, the T_1—T_2 sea basin represented the waning stage of the Paleo-Tethys. T_3—J_1 sea basin was formed in relation with the backarc extension associated with the subduction of the Paleo-Pacific Ocean beneath the Eurasian margin; but during the Early Jurassic high sea level waters of the Meso-Tethys entered the sea basin in large quantity. The J_3—K_1 sea basin was the transitional area of the Meso-Tethys and Paleo-Pacific oceans, the latter was subducting towards the SE margin of the Eurasian continent. The areas now covered by the South China Sea waters were at the margins the T_3—J_1 and J_3—K_1 sea basins, experienced multiple cycles of sea-level variation, and overlain by thick Cenozoic strata. Thus favorable conditions exist for hydrocarbon generation, migration, and accumulation.