Zhongjiannan basin

located in the west of South China Sea

has well developed faults and volcanic rocks

thus the geological conditions are very complex.The influence of the Cenozoic tectonic movement upon the formation and evolution of the basin was huge and is well reflected by its four superposed structural layers with different characteristics in profile

its NNE-NW trending

and its lozenge shape on plane.Both geometrical characteristics of strike-slip basin and geological characteristics of tensional basin can be found in the basin.Centered with a major depression and two secondary depressions

the basin has a structural framework with alternative depressions and upheavals.Extensional structures and strike-slipping structures had been developed in the basin.Different slipping directions brought about completely different effects on the evolution of the basin: sinistral strike caused extrusion while dextral strike slip resulted in extension and subsidence in the basin.The combination of tensile stress and shear stress shaped the area into a strike slip-extensional composite basin after several uplifting and subsidence cycles.