徐家围子断陷沙河子组主干断裂形成演化与地层剥蚀特征

Formation and evolution of main faults and formation denudation characteristics of Shahezi Formation in Xujiaweizi Rift

主干断裂的活动控制着徐家围子断陷沙河子组的建造与改造。为了明确断裂活动,运用位移距离曲线方法系统分析了徐家围子断陷主干断裂的生长活动特征,通过不整合面下的同向轴特征分析了徐家围子断陷沙河子组沉积末期的剥蚀改造作用。结果表明:徐家围子断陷主干断裂分段特征明显,徐西断裂与宋西断裂在火石岭组沉积时期分别是数条分段的小断裂,在沙河子组沉积时期连通为整条断裂并持续控陷活动;徐中断裂在沙河子组沉积时期弱伸展弱控陷,在沙河子组沉积末期作为薄弱带发生压扭反转;徐东断裂带中的徐东正断层在沙河子组沉积时期弱控陷,徐东逆断层在营城组一段沉积末期的反转作用下形成;沙河子组沉积末期的反转作用对沙河子组厚度与构造格局产生明显改变,沿徐西断裂与宋西断裂存在较强的剥蚀,徐西断裂北端升平凸起尤为强烈,徐中断裂压扭反转产生一定的走滑分量并遭受剥蚀,徐东逆断层在营城组一段沉积末期的反转中形成,对沙河子组厚度无明显改变,但对徐东构造带构造格局产生明显影响。研究成果可为徐家围子断陷古构造恢复与进一步勘探提供理论参考。

Main faults activity controls the architecture and reworking of Shahezi Formation in Xujiaweizi Rift.In order to clarify faults activity,the growth activity characteristics of main faults in Xujiaweizi Rift are analyzed sys-tematically by displacement-distance curve method,and the denudation and reworking of Shahezi Formation at sedi-mentary end of Xujiaweizi Rift is analyzed by the characteristics of events under unconformity.The results shows that the main faults of Xujiaweizi Rift have obvious segmentation characteristics.Xuxi fault and Songxi fault were several sub-faults respectively during sedimentary period of Huoshiling Formation,and connected to whole faults during sedimentary period of Shahezi Formation with continuous activities controlling rifting.Xuzhong fault was weakly extensional and weakly controlled rifting during sedimentary period of Shahezi Formation,and with transpressional reverse occurred as weak zone at the end sedimentary period of Shahezi Formation.Xudong normal fault in Xudong fault zone weakly controlled rifting during sedimentary period of Shahezi Formation,and Xudong re-verse fault was formed by reversal effect at the end sedimentary period of the first member of Yingcheng Formation.The reversal effect at the end sedimentary period of Shahezi Formation significantly changed the thickness and struc-tural framework of Shahezi Formation.There was strong denudation along Xuxi fault and Songxi fault,especially the budge at the north end of Xuxi fault.The transpression reversal of Xuzhong fault produced certain strike-slip compo-nent and suffered denudation.Xudong reverse fault was formed by reversal effect at the end sedimentary period of the first member of Yingcheng Formation,with no obvious changing on thickness of Shahezi Formation,but has ob-vious influence on structural framework of Xudong structural belt.The research provides theoretical reference for pa-leostructure restoration and further exploration of Xujiaweizi Rift.