SEISMIC REFLECTION IMAGING OF STRIKE-SLIP FAULT ZONE OF THE NW MARGIN OF THE JUNGGAR BASIN, XINJIANG, CHINA

The fault system in the NW margin of the Junggar Basin, west China, affords an exceptional opportunity to document the structural features of a major strike-slip fault using two- and three dimensional seismic reflection data. The fault zone displays relatively straight faults, positive flower structures and en echelon folds. Three tectonic units, the Zayie-Halat uplift basement belt(Dalabute strike-slip fault), the Kelamay -Xiazijie fault block-en echelon folds belt, and the Mahu lake slop were identified at the NW margin of the Junggar Basin. The Zayie-Halat uplift basement belt is closed to the Dalabute strike-slip fault and developed vertical strike-slip faults. Devonian to Upper Carboniferous volcanic, volcaniclastic and flysch rocks crop out along the belt. The Kelamay-Xiazijie fault block-en echelon folds belt consists of slip faults and en echelon folds. The stepping pattern and orientation of en echelon structures indicate right-lateral sense about N20–40⁰E azimuth of slip in the west part and W-E azimuth of slip in the east part of the Kelamay-Xiazijie belt. The fault segments with clockwise orientation are characterized by convergent structures. The Carboniferous, Permian and Triassic have folded and are unconformity by the Jurassic and Cretaceous, indicating the deformation developed in the Late Permian to Triassic. The exposed Dalabute fault has been reactivated in the Cenozoic, which was affected by the long-distance expression of the Cenozoic India–Asia collision. The NW margin of the Junggar Basin apparently was not deformed in the Cenozoic. Potential hydrocarbon traps form in the Kelamay -Xiazijie fault block-en echelon folds belt where basinward plunging en echelon folds cross sedimentary wedges associated with basin margins, and where large anticlinal culminations are preserved.