北部湾盆地福山凹陷流沙港组湖底扇沉积特征及发育背景
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摘要
福山凹陷流沙港组内发育一套具有一定规模的湖底扇沉积,其中可识别出浊流沉积、水下泥石流沉积和滑塌堆积3种沉积相单元。湖底扇沉积主要发育于低位域及水进早期,地震剖面特征显示为双向下超的丘形反射复合体,测井曲线特征为箱形、钟形或漏斗形。湖底扇在平面上由扇根、扇中和扇端沉积所组成。垂向层序上湖底扇下部常见厚度较大的重力流沉积充填的下切水道,中上部发育多个叠置的浊积扇体组成。湖底扇的发育主要受控于盆地东西两侧的断层活动、湖平面变化及物源供给。流二段时期沉积的较大规模的湖底扇与这一时期的构造快速沉降和充足的物源供给有关。
Some scale of sublacustrine fan deposit was developed in the Liushagang Formation of the Fushan Depression, the Beibuwan Basin. Three main sedimentary facies units can be recognized : turbidity current deposit, underwater debris flow deposit and olistostrome . The sublacustrine fan was developed in the lowstand and transgressive system of the Liushagang Formation. Some bidirectional downlapped reflection structures showed on seismic profiles. The characters of well logging curves are box, bell or funnel type. The sublacustrine fan was composed by three parts on the surface: the proximal, the middle and the distal part. The lower part of the sublacustrine fan vertically developed relatively thick incised valley infilled by gravity flow deposit. Many small turbidite fans accumulated on the vertical sequence. The development of the sublacustrine fan was controlled by the activity of the east and west bilateral faults of the basin, the supply of sediment sources and the change of lake surfaces.The biggerscale sublacustrine fan in the second episode of the Liushagang Formation was related to rapid structural subsidence and sufficient sediment supply.
Some scale of sublacustrine fan deposit was developed in the Liushagang Formation of the Fushan Depression, the Beibuwan Basin. Three main sedimentary facies units can be recognized : turbidity current deposit, underwater debris flow deposit and olistostrome . The sublacustrine fan was developed in the lowstand and transgressive system of the Liushagang Formation. Some bidirectional downlapped reflection structures showed on seismic profiles. The characters of well logging curves are box, bell or funnel type. The sublacustrine fan was composed by three parts on the surface: the proximal, the middle and the distal part. The lower part of the sublacustrine fan vertically developed relatively thick incised valley infilled by gravity flow deposit. Many small turbidite fans accumulated on the vertical sequence. The development of the sublacustrine fan was controlled by the activity of the east and west bilateral faults of the basin, the supply of sediment sources and the change of lake surfaces.The biggerscale sublacustrine fan in the second episode of the Liushagang Formation was related to rapid structural subsidence and sufficient sediment supply.
引文
[1] 杜振川,魏魁生.南海北部湾盆地北部凹陷涠洲组层序地层格架及特征[J].沉积学报,2001,19(4):563-568.
[2] RosendahlBR,ReynoldsDJ,LorberPM,etal.Structuralexpressionsofrifting—lessonsfromLakeTanganyika,Africa[A].SedimentationinAfricanRift[C].GeologicalSocietySpecialPublication,1986,25:29-43.
[3] CohenAS.Tectono stratigraphicmodelforsedimentationinLakeTanganyika,Africa[J].AAPGMemoir50,1991:137-149.
[4] 林畅松,杨 起,李思田.贺兰坳拉槽重力流沉积特征和充填样式[J].现代地质,1991,5(3):252-262.
[5] 林畅松,潘元林,肖建新."构造坡折带"———断陷盆地层序分析和油气预测的重要概念[J].地球科学,2000,5(3):260—265.
[2] RosendahlBR,ReynoldsDJ,LorberPM,etal.Structuralexpressionsofrifting—lessonsfromLakeTanganyika,Africa[A].SedimentationinAfricanRift[C].GeologicalSocietySpecialPublication,1986,25:29-43.
[3] CohenAS.Tectono stratigraphicmodelforsedimentationinLakeTanganyika,Africa[J].AAPGMemoir50,1991:137-149.
[4] 林畅松,杨 起,李思田.贺兰坳拉槽重力流沉积特征和充填样式[J].现代地质,1991,5(3):252-262.
[5] 林畅松,潘元林,肖建新."构造坡折带"———断陷盆地层序分析和油气预测的重要概念[J].地球科学,2000,5(3):260—265.
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