Abstract:

        Urxun Sag in the middle Hailaer Basin is a typical Meso-Cenozoic terrestrial half-graben. In this paper, we firstly illustrate the structural features and evolution of the Hailaer Basin and then analyze the structural geometric characteristics of the seismic reflection profile across the rifting-period prototype basin of the southern Urxun sub-sag. The kink-bands in the hanging-wall are proved to be extensional fault-bend folds. Thus further modeling about the rifting-period prototype basin of the southern Urxun sub-sag can be done to playback the development process of its rifting-period structure with the extensional fault-bend folding theory. The research shows that the evolution of the rifting-period prototype basin of the southern Urxun sub-sag can be divided into four phases: the pre-faulting phase, the initial faulting phase, the intense faulting phase and the stable faulting phase. In fact, its different evolutional phases have different sedimentary thicknesses, different folding styles and different horizontal extensions. Its total extension turns out to be 3.42 km.

Key words: extensional fault-bend folding, Urxun Sag, rift basin, half-graben, forward modeling