Corresponding to the transitional period of the earth system from Late Permian to Early Triassic times （referred to as the P-T transition period）， the Mahu Sag of the Junggar Basin experienced a transition from a foreland basin to a large depression lake basin， with the development of two sets of unconformities（T1/P and P3w/P2w） and two sets of lowstand deposits， the Upper Wuerhe Formation （P3w） and Baikouquan Formation （T1b） that host a series of large or giant conglomerate oil fields. For the two third-order sequence boundaries T1/P and P3/P2， two types of slope-break zones which are associated with flexure or erosion have been identified： flexural slope-break zone is controlled by a persistent paleo-uplift and controls the layer-by-layer “unidirectional onlapping” of the strata above the sequence boundary towards the higher part of the slope； while erosional slope-break zone is controlled by the erosional remnant of plaeo-mounds. It is typically characterized by “two-way onlapping” towards the residual mounds or filling along the lower part of the valleys. The two types of slope-break zones both control changes in stratigraphy and sedimentation， and are conducive to the formation of lithostratigraphic traps of up-dip onlapping， lowstand filling and truncated types. The research results are of great significance to guide the exploration of large-scale lithostratigraphic plays under the control of paleotopography.
Keywords：Junggar Basin
;
Mahu Sag
;
P-T transition
;
Flexural slope-break zone
;
Erosional slope-break zone
CAO Zhenglin, LI Pan, WANG Ruiju. Sequence architecture， slope-break development and hydrocarbon implications of the Mahu Sag during the P-T transition， Junggar Basin. Natural Gas Geoscience[J], 2022, 33(5): 807-819 doi:10.11764/j.issn.1672-1926.2021.12.011
Fig.4
Well sqquence correlation and stacking pattern of the P-T transition of the Mahu Sag，Junggar Basin （modified from Ref.［3］； see location for Fig.1）
Fig.8
Isopach maps and slope break distribution for the P-T transition （Wu'erhe and Baikouquan formations） of the Mahu Sag，Junggar Basin（A-A' and B-B' as shown in Fig.6 and Fig.7）
Fig. 9
Cartoon illustrating the control of two types of slope breaks on deposition during the P-T transition in the Mahu Sag，Junggar Basin（see location for Fig.8）
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... （a）P3w地层分布及其与下伏地层接触关系；（b）P3b地层分布及其与下伏地层接触关系Stratal distribution and contact relationships across the P-T transition in the Mahu Sag，Junggar Basin（modified from Ref.［<xref ref-type="bibr" rid="R3">3</xref>］）Fig.32.2 转换期不整合面及地层分布特征
Well sqquence correlation and stacking pattern of the P-T transition of the Mahu Sag，Junggar Basin （modified from Ref.［<xref ref-type="bibr" rid="R3">3</xref>］； see location for Fig.1）Fig.4
准噶尔盆地玛湖凹陷P—T转换期层序结构样式
Sequence architecture model for the P-T transition of the Mahu Sag，Junggar BasinFig.52.3 转换期层序构成与地层发育模式
... Well sqquence correlation and stacking pattern of the P-T transition of the Mahu Sag，Junggar Basin （modified from Ref.［3］； see location for Fig.1）Fig.4
准噶尔盆地玛湖凹陷P—T转换期层序结构样式
Sequence architecture model for the P-T transition of the Mahu Sag，Junggar BasinFig.52.3 转换期层序构成与地层发育模式
... （a）P3w地层分布及其与下伏地层接触关系；（b）P3b地层分布及其与下伏地层接触关系Stratal distribution and contact relationships across the P-T transition in the Mahu Sag，Junggar Basin（modified from Ref.［<xref ref-type="bibr" rid="R3">3</xref>］）Fig.32.2 转换期不整合面及地层分布特征
Well sqquence correlation and stacking pattern of the P-T transition of the Mahu Sag，Junggar Basin （modified from Ref.［<xref ref-type="bibr" rid="R3">3</xref>］； see location for Fig.1）Fig.4
准噶尔盆地玛湖凹陷P—T转换期层序结构样式
Sequence architecture model for the P-T transition of the Mahu Sag，Junggar BasinFig.52.3 转换期层序构成与地层发育模式
... Well sqquence correlation and stacking pattern of the P-T transition of the Mahu Sag，Junggar Basin （modified from Ref.［3］； see location for Fig.1）Fig.4
准噶尔盆地玛湖凹陷P—T转换期层序结构样式
Sequence architecture model for the P-T transition of the Mahu Sag，Junggar BasinFig.52.3 转换期层序构成与地层发育模式
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