Abstract:

The formation model of pull apart with stepwise dextral strike-slipping of the Beibuwan basin is proposed based on its regional geological background, geometric pattern, basinal boundaries, faulting in the basin, migration of depocenter and internal structures in the basin. The formation and development of the basin is controlled by right stepping fault pattern composed of the Hepu-Beiliu, the Xinyi-Lianjiang, the Wuchuan-Sihui and the Yangjiang-Heyuan fault belts. Flower-like structures developed in the Paleogene show that the basin experienced transtension and consequent structural inversion under transpression in Neogene. This mechanism is simultaneous and similar with Mesozoic-Cenozoic pull-apart basins in South China. The pre-existing deep-seated strike-slipping faults in the basement of the basin are the precedent geological conditions for the formation of the Beibuwan basin in Cenozoic. However, the fundamental factors controlling the formation of the Beibuwan basin are gradual increase of collision of the Indian-Australia to the Eurasia plates coupled with the subduction of the Pacific Plate.

Key words: Beibuwan basin, strike-slip pull-apart, large-scale fault belt, formation mechanism