渤海海域庙西凹陷中南洼古近纪盆地原始形态恢复

Original form restoration in Paleogene of middle and southern sag of Miaoxi depression of Bohai Sea area

庙西凹陷中南洼位于渤中凹陷与胶辽隆起过渡带， 受胶辽隆起差异隆升作用控制， 古近系孔店组、沙四段、沙三段以及东营组沉积之后各组遭受了不同程度的剥蚀。 本文综合 利用声波时差法、镜质体反射率法以及地层厚度变化率法恢复了庙西凹陷中南洼各关键期剥蚀厚度， 再现了庙西凹陷中南洼古近系演化过程。 结果表明， 该区古近纪各沉积期在沉积之后普遍遭受了阶段性抬升剥蚀， 致使各期盆地边界形成多个扩大—收缩旋回， 盆地原形并非小而浅；孔店期—东营期原始盆地沉积边界较现今盆地边界可向东外推 18～25 km；孔店期盆地为统一凹陷， 孔店期之后中、南部洼陷区开始出现差异性隆升—沉降作用， 沙四段沉积期继承孔店期的特点， 差异进一步加大， 沙三段沉积期南、北两个次洼彻底分离， 形成两个孤立洼陷， 东营组披覆沉积两洼之上， 并遭受区域性剥蚀。

Middle and southern sag of Miaoxi depression was located in transition zone of Bozhong depression and Jiaodong-Liaodong uplift. Due to differential uplifting, tops of Paleogene Ek, Es 4 、Es 3 and Ed were denuded in a different degree. Based on data of P-sonic, Ro and change rate of formation thickness method to restore erosion thickness in Paleogene of Miaoxi depression located in east margin of Bohai Sea area. Evolution process in Paleogene of middle and southern sag of Miaoxi depression was obtained. The results showed that, uplift-erosion occurred periodically in Paleogene after sedimentary occurred, which maked the boundary move in several forward-backward cycles. Original basin is not small and shallow, from Ek stage to Ed stage, original boundary were in the east 18～25 km off. It is a whole sag in Ek, After which, middle and southern sag of Miaoxi depression began to uplift and deposit differently, which developed in Es 4 , the two sags separated completely and independent sags fom in Es 3 . Drape deposit was reformed by regional erosion after covering the two sags in Ed.