沉积旋回与相-2课件

TeachingMaterialChapter2IntroductionofSedimentaryCyclesSedimentaryCyclesandFaciesAnalysisContentsConceptClassificationofSedimentaryCyclesDescriptiveclassificationGeneticClassificationRecurrenceTimeofCyclicandDiscyclicBeddingFourBasicTypesofSedimentaryCyclesConceptSedimentarycyclesagroupofrockunitsthatoccurinacertainorder,withoneunitbeingrepeatedfrequentlythroughoutthesuccession(DuffandWalton,1962).可重复重现的一组岩相或岩相组合RepresentedbyaseriesofeventsthatarenormallyrecurrentandrepeatedinasameorderACBBACCABConceptRhythmicBeddingandSedimentaryCyclesofDifferentScales

VarioussedimentarysuccessionRhythmicsuccession:

twoalternatingbedtypes(successionAB,AB)AAABBConceptRhythmicBeddingandSedimentaryCyclesofDifferentScales

VarioussedimentarysuccessionCyclicsuccession:

severaldifferentsedimenttypes,atleastthree,formingasuccession (e.g.,ABC,ABC,etc.)ClassificationofSedimentaryCyclesDescriptiveclassificationGeneticClassificationRecurrenceTimeofCyclicandDiscyclicBeddingFourBasicTypesofSedimentaryCyclesDescriptiveclassification

RepetitionofrhythmicandcyclicbeddingSlowgradualchanges:cyclicbedding,orperiodicbeddingwithstrictlyperiodallocyclic,e.g.,orbitalclimaticphenomenaExample:chalk-marlcyclesDescriptiveclassification

RepetitionofrhythmicandcyclicbeddingSlowgradualchanges:Descriptiveclassification

RepetitionofrhythmicandcyclicbeddingAbruptchangesofbeddingvariationsdepositionaleventsorepisodesatrandomtoquasi-periodictimeintervals(stochastic,episodic,anddiscyclicbedding)Examples:

tempestites,

turbiditesChannelFillingTurbiditeDescriptiveclassification

RepetitionofrhythmicandcyclicbeddingAbruptchangesofbeddingvariationsDescriptiveclassification

ScaleofrhythmicandcyclicsedimentsVarve-scalelaminationsBed-scalerhythmsandcyclesField-scalesedimentarycycles100kyr-severalm.y.,20-100kyr

Macroscalecyclicsequences100m-severalkm,10m.y.-100m.y.-Einsele,1991DescriptiveclassificationGeneticClassification

ControllingfactorsAutocyclicsuccession

Cyclothemicdepositionthatrequiresnochangeinthetotalenergyandmaterialinputintoasedimentarysystembutinvolvessimplytheredistributionoftheseelementswithinthesystem.Itinvolvessuchmechanismsofdepositionaschannelmigration,channeldiversion,andbarmigration.GeneticClassification

ControllingfactorsAllocyclicsuccession

Cyclothemicdepositionthatresultsfromchangesinthesupplyofenergyormaterialinputintoasedimentarysystem.Itinvolvessuchmechanismsasuplift,subsidence,climaticvariation,eustaticchangeinsealevel,andotherchangesexternaltothesedimentaryunit.GeneticClassification

Timeperiodsofsedimentarycycles(Vailetal.,1987;Haqetal.,1987)

First-andsecond-ordercycles:Third-ordersequences:0.5to5m.y.Fourth-ordercycle:0.1to0.5m.y.eustaticvariationsFifth-ordercycle:0.01to0.1m.y.MilankovitchfrequencybandSixth-ordercycle:shorter10kyr

MilankovitchvariationsRecurrenceTimeofCyclicandDiscyclicBedding

StrictlyperiodiccycleExample:11-yearsunspotcycles,Milankovitchcyclesquasi-periodiccycleExample:tidal,rotational,andorbitalparametersRecurrenceTimeofCyclicandDiscyclicBedding

Characteristics Longer-term,third-ordersealevelvaryingtimeperiodswithinacertainorderofmagnitude

superpositionofseveralmechanismofdifferingtimeperiodsdifficulttofindoutfromtheresponseofsedimentswhetherthereisatrueperiodicprocessinoperationabovethedepositionalbackgroundnoiseRecurrenceTimeofCyclicandDiscyclicBedding

nonperiodiccycle(episodicevent)Example:turbiditeortempestit,epibenthicshellbedsEpibenthicshellbedsoccurthroughoutthePhanerozoic.Ifthecoarseparticlesareproducedinplacebybiologicalprocesses,boundaryshellbedscanbeplacedintotheongoingtransgression-peak.Truth:

Thebackgroundsedimentisdiscontinuouslyinterruptedbylaterallytransported,allochthonousturbiditesediment.FourBasicTypesofSedimentaryCycle

Origin:

Anempiricalclassificationofsedimentarysequencesusingrank-orderdesignations,basedontheirduration.

-Vailetal.,1977Counterview:althoughahierarchyofsequencesexistsinthestratigraphicrecord,theirdistinctivenessintermsofdurationorrecurrenceintervalisonlyapproximate. -Carteretal.,1991

2.4FourBasicTypesofSedimentaryCycle

Counterview:quantitativestudyofthedurationandthicknessofstratigraphicsequences

-Drummond&Wilkinson,1996

discriminationofstratigraphichierarchiesandtheirdesignationasnth-ordercyclesmayconstitutelittlemorethanthearbitrarysubdivisionofanuninterruptedstratigraphiccontinuumStratigraphiccyclesandtheiroriginsTheSupercontinentCycleCharacters:

Fourcycles,spanning200-500m.y.=first-ordercycles-Vailetal.,1977LateCambriantoMississipian MaximumtransgressionCretaceous MaximumtransgressionPennsylvaniantoJurassic MaximumregressionOrigin:assemblyofsupercontinentsbyseafloorspreading,riftinganddispersal

Majorcyclesofsea-levelriseandfallduringthePhanerozoicSupercontinentCycleSupercontinentCycleSupercontinentCycle87Sr/86Sr–Basalt:0.704Weathering:0.705~0.735SeaLevelandClimateFIVEORDERSOFCYCLESCycleswithEpisodicitiesofTensofMillionsofYearsCharacters:

SixcyclesinPhanerozoic

-Sloss,1963detailedisopachandlithofaciesmapsoftheWesternCanadaSedimentaryBasinandtheRussianPlatform.Thedatafromtwoareasshowremarkablesimilarities,andconfirmsthatSloss'ssixsequencescanberecognizedintwoseparatedcontinents.Origin:

global,eustaticchangesinresponsetovolumechangesinoceanicspreadingSixsequencesofSloss(1963)FIVEORDERSOFCYCLESCycleswithMillion-YearEpisodicitiesCharacters:

1-10m.y.

=thi