珠江口盆地新近纪海平面升降过程及其对砂体的控制

通过沉积相序的变化识别出地层叠加样式，并定性判断单井上海平面升降变化过程。以此为基础，采用了连井沉积 相对比分析沉积相带的迁移过程，通过对削截、上超等地震反射轴的终止形式和前积体叠置关系进行分析，对珠江口盆地 新近系层序地层进行了划分和对比，并刻画了该区域新近纪海岸上超过程，进而构建了海平面升降曲线。随着海平面的升 降，古珠江三角洲的发育范围不断减小或扩大，而且三角洲还发生不同程度的侧向迁移。海平面变化促使有利砂体发育场 所两极化。海平面较低时，陆架坡折以下的陆坡内凹陷成为有利砂体发育的场所，主要发育低位体系域的重力流成因扇体 和楔状前积砂体；海平面较高时，陆架内凹陷成为有利砂体发育的场所，主要发育的砂体类型包括海侵期和高位期的中陆 架和内陆架三角洲砂体。
DuringtheLateTriassic,theslopebreakbeltofdepressionlakebasinwasdevelopedintheOrdosBasin.Basedontherock types,faciesassociations,andseismicreflectioncharacters,thedeep-waterslopebreakbeltswererecognizedinthesouthwesternand northeasternpartofthelakebasin,whichwerenamedasthesouthwestslopebreakbeltandthenortheastslopebreakbeltaccordingly. Theterrainslopewascalculatedwiththerateofformationthicknesschange,andthustheslopebreakpointswereorientatedtoidentify thedistributionofslopebreakbeltsduringtheChang7-Chang6period.Thesouthwesternslopebreakbeltisoflargescale,whilethe northeasternoneissmaller.Theslopebreakbeltsobviouslyhavecontrolsonsandbodies,mainlyreflectedinthreeaspects:origin types,thicknessvariations,anddistributionalmorphology.Uponthedeep-waterslopebreaks,sandbodiesofdeltafrontweredeveloped. However,underthedeep-waterslopebreaks,sandbodieswereformedmostlybygravityflows,suchassublacustrinefanandslump olistolith.Meanwhile,differenttypesofgravityflowssandbodiesdevelopedinsteepslopebeltandgentleslopebelt.Thethicknessofsandbodiesfromthesameprovenancedecreasedfirstlyandthenincreasedfromtheupperslopebreakbelttotheslopetoe.Uponthe slopebreakbelt,sandbodiesoccurinstripsorasasheet.Undertheslopebreakbelt,theirpatternsvariedaccordingtotheterrainslope andthedistancetotheslopetoe.