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