Abstract：
The Mahu sag in the northwestern margin of the Junggar Basin is one of the most important hydrocarbon-rich sags
in the Junggar Basin. The understanding of basin attributes and tectonic evolution of the Junggar Basin during the Permian-early
Triassic is significant for oil and gas exploration and development. The Permian to early Triassic terrestrial successions in the
Mahu sag record the tectonic evolution of the northwestern margin of the Junggar Basin. Comprehensive studies of structures,
sequence stratigraphy, sedimentary infill, sediment dispersal and paleogeographic construction were performed on the
Permian-early Triassic successions. 2D seismic profiles show the occurrences of basin-bounding normal faults and half-graben
structures during the Early Permian and the tectonic inversion during the late Permian to early Triassic. Widespread soft-sediment
deformation structures in the lower Permian Fengcheng Formation with lateral continuity correspond with the main activity on
basin-bounding normal faults. The Permian to Triassic strata are organized into two second-order transgressive-regressive (T-R)
sequences. During the early Permian, sediments of transgressive systems tracts 1 recorded depositional system transition from
fan delta to deep lacustrine setting, and the depocenter was distributed along the boundary normal fault. At this time, tectonic
mechanical subsidence exceeded sediment supply. During the middle Permian, the depositional system of regressive system
tracts 1 transitioned from lacustrine to fan delta setting, and the location of the depocenter shifted to the center of the Mahu sag,
where thermal subsidence played a great role. During the late Permian-early Triassic, fan-deltas were distributed along the Hong
Che, Ke-Bai and Wu-Xia fault zones. Therefore, three stages of the tectonic evolution of the Permian-early Triassic Mahu in the
northwestern margin of Junggar Basin are recognized: early Permian syn-rift mechanical subsidence, middle Permian post-rift
thermal subsidence, and late Permian to early Triassic tectonic inversion. The dynamic mechanism of the tectonic evolution of
the northwestern margin of the Junggar Basin is consistent with the evolutionary pattern of the late Paleozoic post-accretionary
orogenic stage in the southwestern margin of the Central Asian Orogenic Belt
.
Key words：west Junggar Basin; Permian; basin attributes; Mahu sag; rift basin; tectonic inversion
Corresponding Authors： yy-zhang@pku.edu.cn
Cite this article：张元元, 曾宇轲, 唐文斌. 准噶尔盆地西北缘二叠纪原型盆地分析. 石油科学通报, 2021, 03: 333-343 ZHANG Yuanyuan, ZENG Yuke, TANG Wenbin. Permian attributes and tectonic evolution of the west Junggar Basin. Petroleum Science Bulletin, 2021, 03: 333-343.
