关键词: 地层叠加样式；海平面升降；新近纪；白云北坡；珠江口盆地

Abstract:

    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.

Key words: slopebreakbelt;gravityflows;OrdosBasin;YanchangFormation