Structure and evolution of faults in central and northern parts of Tazhong Uplift, Tarim Basin

Abstract

Objective To reveal the structures and evolutionary patterns of faults in the central and northern parts of Tazhong Uplift, Tarim Basin, Methods this paper systematically discusses the types of fault structures, geometric characteristics, differential activity mechanisms, and tectonic evolution processes in this area by analysing detailed structural interpretations and coherent slices of combined large 3D seismic data along with the regional dynamic background. Results The results show that there are 4 types and 7 evolution stages of faults in the central and northern parts of Tazhong Uplift, among which thrust faults and strike-slip faults are particularly common. On the plane, NW arc thrust faults intersect with NE-, NW- and NS-striking strike-slip faults; vertically, the fault stratification and differential activity characteristics are obvious. In the Lower Ordovician and the belowing layers, faults developed in large numbers and were mainly linear in their trending directions. As for the Middle Ordovician-Middle and Lower Devonian layers, faults are mostly in the echelon type. In the Upper Devonian-Permian layers, a few faults developed in the Tazhong Ⅱ fault zone and the southwestern end of the Shunbei 5 fault zone. Conclusion The fault activity in the study area was controlled by stress sites exhibiting diverse properties across multiple phases and directions and experienced an extremely complex evolutionary history: In the Early Caledonian period, a small number of normal faults, such as the Tazhong Ⅱ fault zone, were mainly active; in the Middle Caledonian Ⅰ period, the fault activity was very strong and was characterized by coevolution and mutual coupling of thrust faults and strike-slip faults. The strike-slip faults obviously cut or restricted the thrust faults. The fault activity of the Middle Caledonian Ⅲ period basically inherited the tectonic framework of the Middle Caledonian Ⅰ period, but the characteristics of transtensional fault activity in the Shunbei 4 and 5 fault zones are significant. From the Late Caledonian to Early Hercynian, some of the faults inherited activities with obvious transtensional characteristics. Conversely, in the Indochina-Yanshan period, only a few faults inherited activity, and the development area of transtensinal fault is further expanded to the south. During the Himalayan period, the tectonic movement of this area was relatively stable, and the complex fault structures that formed in the early stage transitioned into the deep burial stage.

Keywords

• thrust fault
• strike-slip fault
• transtensional fault
• structure and evolution
• central and northern parts of the tazhong uplift
• tarim basin