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TitlePermian to early Triassic tectono-sedimentary evolution of the Mahu sag, Junggar Basin, western China: sedimentological implications of the transition from rifting to tectonic inversion
AuthorTang, W B; Zhang, Y Y; Pe-Piper, G; Piper, D J WORCID logo; Guo, Z; Li, W
SourceMarine and Petroleum Geology vol. 123, 104730, 2020 p. 1-15,
Alt SeriesNatural Resources Canada, Contribution Series 20200050
Mediapaper; on-line; digital
File formatpdf; html
Lat/Long WENS 82.0000 87.0000 47.4167 45.0000
Subjectsstratigraphy; sedimentology; tectonics; geophysics; fossil fuels; Science and Technology; Nature and Environment; sedimentary basins; tectonic evolution; rifting; depositional history; subsidence; core samples; geophysical logging; well logging; geophysical surveys; seismic reflection surveys; isopachs; lithofacies; deltas; fans; alluvial fans; lacustrine deposits; paleogeography; bedrock geology; structural features; grabens; fault zones; peneplains; sediment dispersal; dispersal patterns; petroleum resources; hydrocarbon potential; hydrocarbons; gas; oil; stratigraphic correlations; Junggar Basin; Mahu Sag; Hong-Che Fault Zone; Ke-Bai Fault Zone; Wu-Xia Fault Zone; Phanerozoic; Mesozoic; Triassic; Paleozoic; Permian
Illustrationslocation maps; geoscientific sketch maps; stratigraphic cross-sections; stratigraphic charts; tables; photographs; lithologic sections; seismic profiles; correlation sections; 3-D models
Released2020 09 29
AbstractThe Permian to early Triassic terrestrial successions in the Mahu sag constrain the tectonic evolution of northwestern edge of the Junggar basin. This study analyzes the sequence stratigraphy of the Mahu sag in order to understand the interplay between tectonic processes and the sedimentary fill of the basin. It uses detailed analysis of drill cores, geophysical well logs, 2D seismic reflection profiles and isopach maps. Sixteen lithofacies are grouped into three facies associations: fan delta, fluvial delta and lacustrine. The Permian to Triassic strata are organized into two second-order transgressive-regressive (T-R) sequences, further separated into transgressive systems tracts (TST) and regressive system tracts (RST). Based on seismic profiles, paleogeographic facies distribution and isopach maps, two stages of tectonic evolution are recognized: 1) early Permian syn-rift to middle Permian post-rift; 2) late Permian to early Triassic tectonic inversion. During the early Permian, sediments of TST1 record two cycles of depositional system transition from fan delta to deep lacustrine setting within the half-graben structure shown by 2D seismic profiles. At this time, tectonic mechanical subsidence exceeded sediment supply. The middle Permian post-rift stage (RST2) is characterized by gradual and slow peneplanation, which is documented by sediment supply exceeding thermal subsidence, so that the location of depocenter shifted and the depositional system transitioned from lacustrine to fan delta setting. Late Permian-early Triassic tectonic inversion is demonstrated by a striking change of the sediment dispersal patterns along the Hong-Che, Ke-Bai and Wu-Xia fault zones and alluvial fan deposition at the base of TST2. Tectonism is the main factor controlling sediment dispersal, paleogeographic evolution and hence hydrocarbon accumulation, providing a new perspective to oil and gas exploration and development in the Mahu sag.
Summary(Plain Language Summary, not published)
The Junggar Basin in western China is a major petroleum producing basin with similarities to the Maritimes Basin of Atlantic Canada and Gulf of Saint Lawrence. This study describes in detail the sedimentation environments and tectonic deformation during the early history of the Junggar Basin and their significance for petroleum geology of the basin.

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