Extensional structures and basin evolution of the Wunite depression in Erlian Basin

The Wunite depression is one of the five depressions in the Erlian Basin. A series of grabens/half grabens were developed under the action of regional extension in Early Cretaceous. Extensional fault and transform structure form the extensional structures. The major boundary faults (MBF) are listric faults, slipping deep in the mélange zone and being shallow in complex synclines. The MBF extends like a simple arc or a wave. Accommodating/propagating displacement is realized through transfer fault or strike ramp. Divergent TZ and convergent are the main transfer structures between faulted-sags. And the MBF tendency often changes through the divergent or convergent TZ. In the early Early Cretaceous, lots of independent small-scale faulted-sags filled Wunite Depression; in middle Early Cretaceous, with the continuing of extension, adjacent faults were laterally propagating to become the regional boundary fault and adjacent faulted-sags were connected to become the complex faulted-sag; in late Early Cretaceous, the depression entered into the post-rifting stage.