Unconformity Types, Disconformity, Nonconformity - Geology ...

Disconformities are usually erosional contacts that are parallel to the bedding planes of the upper and lower rock units. Since disconformities are hard to ... HomeGeneralRocksIgneousRocksSedimentaryRocksMetamorphicrockMineralsPhysicalPropertiesOpticalPropertiesBranchesEngineeringGeologyMineralDepositPetroleumGeologyHydrogeologyElementsofTheHydrologicCycleEvaporationandTranspirationGeophysicsFieldMethodsStructuralGeologyDisasterEarthGeologicTimeScaleEarthInteriorPlateTectonicsGalleryQuestionsSearchContactPrivacyPolicySigninWelcome!LogintoyouraccountyourusernameyourpasswordForgotyourpassword?GethelpPrivacyPolicyPasswordrecoveryRecoveryourpasswordyouremailApasswordwillbee-mailedtoyou.GeologyScienceHomeGeneralRocksIgneousRocksSedimentaryRocksMetamorphicrockMineralsPhysicalPropertiesOpticalPropertiesBranchesEngineeringGeologyMineralDepositPetroleumGeologyHydrogeologyElementsofTheHydrologicCycleEvaporationandTranspirationGeophysicsFieldMethodsStructuralGeologyDisasterEarthGeologicTimeScaleEarthInteriorPlateTectonicsGalleryQuestionsHomeMethodsofGeologyUnconformitiesMethodsofGeologyShareFacebookTwitterPinterestWhatsAppLinkedinEmailTumblrTelegramVKAnunconformityarecontactbetweentworockunits.Unconformitiesaretypicallyburiederosionalsurfacesthatcanrepresentabreakinthegeologicrecordofhundredsofmillionsofyearsormore.Itcalledanunconformitybecausetheagesofthelayersofrockthatareabuttingeachotherarediscontinuous.Anexpectedageoflayerorlayersofrockis/aremissingduetotheerosion;and,someperiodingeologictimeisnotrepresented.UnconformitiesDisconformity Disconformities areusuallyerosionalcontactsthatareparalleltothebeddingplanesoftheupperandlowerrockunits.Sincedisconformitiesarehardtorecognizeinalayeredsedimentaryrocksequence,theyareoftendiscoveredwhenthefossilsintheupperandlowerrockunitsarestudied.Agapinthefossilrecordindicatesagapinthedepositionalrecord,andthelengthoftimethedisconformityrepresentscanbecalculated.Disconformitiesareusuallyaresultoferosionbutcanoccasionallyrepresentperiodsofnondeposition.DisconformitybetweenmassiveCoconinoSandstoneandthinnerbeddedHermitShale,GrandCanyonNonconformityA nonconformity isthecontactthatseparatesayoungersedimentaryrockunitfromanigneousintrusiverockormetamorphicrockunit.Anonconformitysuggeststhataperiodoflong‐termuplift,weathering,anderosionoccurredtoexposetheolder,deeperrockatthesurfacebeforeitwasfinallyburiedbytheyoungerrocksaboveit.Anonconformityistheolderosionalsurfaceontheunderlyingrock.NonconformityintheGrandCanyonAngularUnconformityAn angularunconformity isthecontactthatseparatesayounger,gentlydippingrockunitfromolderunderlyingrocksthataretiltedordeformedlayeredrock.Thecontactismoreobviousthanadisconformitybecausetherockunitsarenotparallelandatfirstappearcross‐cutting.Angularunconformitiesgenerallyrepresentalongertimehiatusthandodisconformitiesbecausetheunderlyingrockhadusuallybeenmetamorphosed,uplifted,anderodedbeforetheupperrockunitwasdeposited.AngularUnconformityatTelheiroBeach,PortugalButtressUnconformityAbuttressunconformity(alsocalledonlapunconformity)occurswherebedsoftheyoungersequenceweredepositedinaregionofsignificantpredepositionaltopography.Imagineashallowseainwhichthereareislandscomposedofolderbedrock.Whensedimentationoccursinthissea,thenewhorizontallayersofstrataterminateatthemarginsoftheisland.Eventually,asthesearises,theislandsareburiedbysediment.Butalongthemarginsoftheisland,thesedimentarylayersappeartobetruncatedbytheunconformities.Rocksbelowtheunconformitiesmayormaynotparalleltheunconformities,dependingonthepre-unconformitystructure.NotethatabuttressunconformitydiffersfromanangularunconformityinthattheyoungerlayersaretruncatedattheunconformitiessurfaceButtressUnconformity,NorthernArizona.UnconformitiesFormNonconformitiesareduetorelativechangesinsealevelovertime.Wavewearcorrodesthematerialsexposedonthecoastlineandsmoothessurfaces.Atthousandstomillionyearsofscale,thecoastlinecanmoveinallregions.Removesmaterialsexposedtoerosion,waveandcurrent.New(younger)materialsmaybedepositedontheengravedsurface.Shallowseasmayfloodinandthenwithdrawalrepeatedly.Long-lastingtransgressionscanerodeawayentiremountainrangeswithenoughtime.Atransitionoccurswhenacoastlinemigratestowardslandasthesealevel(orlakelevel)rises.Aregression occurswhenacoastlinemigratestowardstheseawhenthecoastfallstosealevel(orlakelevel).Sea-levelchangesmayresultfromregionalupliftsorglobalsea-levelchanges,suchastheformationormeltingofcontinentalglaciers.Regardlessofthereasonforthechangeofsealevel,whenthesealevelfalls,sedimentserodefromexposedsoils.Whenthesealevelrises,sedimentsaretypicallydepositedinshallowcontinentalshelvesorcoastalplains,suchasinlow,swampyareas,inquietwaterenvironments.QUESTIONSMARK?WhatwasthePrecambrian?Whataresomesubdivisionsofgeology?WhatisGeology?TheEarth’sLayersWhatelementsarefoundintheEarth’satmosphere?TableofContentDisconformityNonconformityAngularUnconformityButtressUnconformityUnconformitiesFormAPAMLAHarvardVancouverChicagoIEEEGeologyScience(1January2022)Unconformities.Retrievedfromhttps://geologyscience.com/methods-of-geology/unconformities/."Unconformities."GeologyScience-1January2022,https://geologyscience.com/methods-of-geology/unconformities/GeologyScience13June2018Unconformities.,viewed1January2022,GeologyScience-Unconformities.[Internet].[Accessed1January2022].Availablefrom:https://geologyscience.com/methods-of-geology/unconformities/"Unconformities."GeologyScience-Accessed1January2022.https://geologyscience.com/methods-of-geology/unconformities/"Unconformities."GeologyScience[Online].Available:https://geologyscience.com/methods-of-geology/unconformities/.[Accessed:1January2022]>ContactPrivacyPolicy©Copyright©2018Allrightsreserved.Gotomobileversion