The Evolution Of Extensional Direction Around The Middle Segment Of The Tanlu Fault Zone

The long-term rifting of Cretaceous to Paleogene during craton destruction and lithospheric thinning of the eastern North China Craton (NCC) provides a good opportunity to understand evolution of extensional direction and geodynamic setting of the destruction. Cretaceous-Paleogene rift basins around the middle segment of the Tan-Lu fault zone in the eastern NCC were chosen for studies in this work. On the basis of basin depocenter patterns and normal fault slip data, it is shown that the extension experienced an evolution from WNW-ESE extension of the earliest-middle Early Cretaceous, NW-SE extension of the latest Early Cretaceous to nearly N-S extension of the Late Cretaceous-Paleogene. Correlation of the extensional directions in the eastern NCC and oceanic plate motions show that they were parallel to each other. It is suggested therefore that the extensional direction evolution was controlled by the oceanic motion and the craton destruction took place under a back-arc spreading setting. The coupling relation between the directions of the overriding plate extension and oceanic plate motion supports the slab rollback model for the back-arc extension. It is proposed that the trench retreat direction generally parallel to the oceanic plate motion directly controls the extension direction in the overriding plate.