黄骅坳陷新生代沉降中心迁移:数值模拟证据

在详细调研前人成果的基础上,参考最新的地震解释资料,绘制了黄骅坳陷新生代各期地层古厚度图,并由此重建了黄骅坳陷古地貌形态,认为黄骅坳陷新生代沉降中心具有由南向北再转向东迁移的特点。通过对该区域新生代构造沉降演化进行数值模拟实验,认为造成这一迁移的主要机理在于在欧亚大陆与印度板块碰撞及伊佐奈崎板块和菲律宾板块向西俯冲于欧亚板块之下的综合应力作用下,黄骅坳陷两条控盆边界断层先后开始活动.首先在沧东断层弯曲的应力集中部位产生裂陷,后羊二庄等兰聊断裂延伸端也开始活动,使得沉降中心沿沧东断层向北迁移,由于受到新港潜山构造带影响,古近纪末期开始转向东部海域迁移,新近纪时迁移至现今最大沉降中心歧口凹陷。

Subsidence Center Migration of the Huanghua Depression in Cenozoic: Evidence of Numerical Modeling

Basin formation mainly results from subsidence.The subsidence history of a basin contains huge information such as regional dynamic settings,structural attribution of basin,provenance characteristic,fluid dynamic,and so on.Isopach change is positive correlation to the amount of subsidence range variety and can be used to investigate the paleo-relief,while the paleo-relief reflects the subsidence center of the basin.Based on thorough analyses of documents available and the new seismic data,the authors mapped the isopach maps of each stage of Cenozoic and rebuild the paleo-relief of the Huanghua depression.It is most likely that the subsidence center of the Huanghua depression in Cenozoic migrated northwards along the Cangdong fault and then eastwards.A numerical modeling has been carried out to stimulate the structural subsidence of the Huanghua depression in Cenozoic.It is suggested that activity of the boundary faults bounding the basin was the main mechanism for the migration,whereas the activity of the faults was droved by the stresses of the collision between the Eurasia and India plate,and the subduction of the Izanaqi and Philippine plate underneath the Eurasia plate.First,the Cangdong Fault formed small pull-apart sag at the bendding part.Secondly,the activity of the Lanliao fault led to the northwards migration of the subsidence center along the Cangdong fault.And finally,turned eastwards and reached the largest subsidence center nowadays-the Qikou sag.