1)Ooids

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WAPBG

Miamioolites(left) *TheWAPBGTS,isanooidgrainstoneaccordingtoDunhamsclassification,A)ModernMiamioolitesdemonstratetwodifferenttypesofmicrofabrics:somehavetangentialandothershavearandomfabricofaragonitecrystals.Incontrast,theCarboniferousooidsprimarilyhavearadialconcentricmicrofabric.Alsonotethatanintragranularfabricexistswith

ooidsarepreferentiallyfoundinareasofmaximumagitation,howeverradialooidscanformfromturbulentenvironmentsaswell.2)Peloids

AKABAHPeloids

A)Therearemanypossiblemodesoforiginofpeloids:fecalpellets,calcareousalgae,micritisedgrains,smallintraclasts,mudclastsoraprecipitateorigin.Depositfeedinganimalsproducefecalpeloids.Peloidscanalsorepresentmicritisedgrainssuchasabradedshellfragmentsorooids.Theyalsocanberemnantsoffinegrainedalgalremainsorformbythecalcificationofcyanobacteriainalgalmats.Manypeloidsaresimplysandsizedintraclastsorlithoclastsderivedfrompreexistingmicriticsubstrates.Finallytheycanalsobechemicalinoriginandrepresentcementsinwhichthepelletsaresitsofsmallcrystalsofhighmagnesiumcalcite.

B)Peloids,composedofmicrocrystallinecarbonate,areanimportantconstituteofshallowmarinecarbonatesedimentsandaretypicalofshallow,lowenergy,restrictedmarineenvironments.

3)Intraclasts

MaynesHandSample(below)WJM608TS(above)

A)Intraclastsformedfrompoorlysortedweaklyconsolidatedsedimentthatisreworkedfromwithintheareaofdeposition.Thisprocessconsistsofdepositioninariversinterchannelarea,followedbyquicklithificationofmudandthenerosionbyfluvialaction.

4)Pisolites

PR10HandsampleandThinsample

A)Accordingtomyobservations,thesearevadosepisolites,sincetheyarequitelargerandhaveseverallayersofisopachouscoatings,manywithstalactitictexture(duetogravity)asindicatedonthediagramabove.Tofurthersupportmyclaim,thesepisolitessharefittedlaminaeasshowninthediagramaswell.

5)Birdseye(Fenestral)Fabric

6)Cyanobacteria:AlgalLaminates,StromatolitesandOncolites

A)Asshowninthediagramabove,DT20showsevidenceofalgalfilamentmolds,thesewhitecalcifiedmicrobialfilamentmoldsaregenerallynormaltobedding.B)Theselaminationsareformedbysedimentssuchassanddepositedontidalflatsandtrappedbymicrobialalgalmatswhichconsistoflayersoffilamentousandunicellularmicroorganismsmainlycyanobacteria.Thisalternatingdepositionalpatternofsandandalgaematsisthenrepeatedseveraltimes.

C)ThealgaelaminationsofDT20andMI11probablyformedinalowenergyenvironmentsuchasarestrictedbayarea,whereastheKinbladeandrecentstromatolitesprobablyformedinthehighenergyenvironmentsuchastheintertidalzone.D)Oncolitesusuallyforminasimilarfashionascyanobacterialaminationsformexcepttheyformradiallayersaroundacentralnucleussuchasashellfragment;calciumcarbonateisprecipitatedbyencrustingmicrobes(cyanobacteria),causingalayeredsphericalgrowthstructure,facilitatedbythecyanobacteriagrowth.Oncolitesareverysimilartostromatolites,butinsteadofformingcolumnstheyformsphericalstructures.7)RedAlgae

A)Thegoniolithonredalgaealsocalledcorallinehaveadistinguishbranchingshellstructure,notethefinescalepolygonalcellularstructure.Theirmultilayeredcoaxialskeletalstructureconsistsofamedulla(centralpart)extendingupwardstothenextsegmentcomposedof

partitionedfilamentsandperipheralcellularfilamentssurroundthemedulla.Othersamplesshowanencrustingform.B)Redalgaeareavaluablepaleoenvironmentmarker.Althoughtheyneedsunlighttocarryoutphotosynthesistheyarenotalwaysindicativeofashallowtropicalwarmwatermarineenvironment.Theyhavebeenfoundtoflourishasdeepas250meters,aslongaslightcanreachthem.Redalgaecangrowintemperateandcoldwaterclimatesaswell.Theypreferagitatedwaterenvironments,suchasintheinnerramp.Thereefframeworksandmorphologyofredalgaebranchesreflectdifferentwaterenergies.Forexample,redalgaearethedominantorganismofmostancientcarbonaterimmedshelves.8)GreenAlgae

*AccordingtoDunhamclassification,PSMismostlyanalgalwackestonealthoughtherearesomeareasthatmaybeconsideredaalgalpackstone.A)Sincegreenalgaecanonlyexistinwarmtropicalwatersinlowlatitudestheyindicateawarmtropicalpaleoclimate.Alsotheyareunabletogrowindeepwaterandthereforeindicateashallowmarineenvironment,suchasintheouterramp.Theyarecommoninquietlagoonsbutarealsofoundinlessturbulentpartsofopenshelvesandreefswheresunlightpenetrationisabundant.3)Mollusks

*AccordingtoDunhamsclassification,KLFIisamolluskangrainstone.A)TherearetwotypesofshellpreservationinMiamiMollusks;somearepreservedasmolds(voids)sincethearagoniteshellitselfhasdissolvedaway.Othershellsarepreservedascasts(moldfilling)thiscalcitizationpreservestherelicmicroarchitectureofthearagonite.B)Therearetwomajortypesoffabric:Thefirstisaprimarystructurethatisindicativeoftheoriginalbiogenicshell,consistingoffibrouscrystalthatareorientatedperpendiculartotheshell.Thesecondisamicriticfabric,sincethearagoniteshellsarehighlyunstableandhavebeendiageneticallyalteredbyleachingproducingmicriticenvelopes.Therearealsodifferentporositytypespresent:Thereisintragranularfabric,adiageneticstructure,theinteriorofsomeshellsisdissolvedawaybyleaching,somehavebeencompletelydissolvedcausingadiageneticmouldicfabric.TherealsoisIntergranularporosity,aprimarystructure.(IwasconfusedbythewordfabricsoIgavetwoanswers)

10)Brachiopods

A)Thesebrachiopodshavealowanglefibrouswallstructurewhichisdifferentfromthanthehighangle(nearlyperpendicular)lamellarwallstructure(narrowbandsoflight/darkextinction)andofthemollusks.11)Echinoderms

*AccordingtoDunhamsclassification,BURL1isaechinodermiangrainstoneinmostareasbutcanbeconsideredcoarsegrainedcrystallineinothers.A)Echinodermshavefivefoldsymmetry,singlecrystalextinctionandaholeyfabric(smallporesthatappearastinyblackspots).Asancientshellslostmagnesiumcalcite,theholesgetfilledinandthecementtakesonthesameorientationoftheechinoderms,thisiscalledsyntaxialovergrowth.12)Bryozoa

*AccordingtoDunhamsclassification565018isabryozoanwackestone,althoughsomeareasofthethinsectioncanbeclassifiedasabryozoanpackstone.A)Themicrostructureconsistsofchamberscalledzooeciathatarearrangedineitheraradiallacypatternoranelongatedstickpattern.Notethefinelyfibrouswallstructure.

13)Stromatoporoids

A)Thetabular,anddendroidgrowthmorphologiesarelabeledinthediagramabove.

14)Corals

*AccordingtoDunhamsclassificationscheme,HG44,isprimarilyacoralineboundstone.A)Thecoralwallismadeoutofbundlesofaragonitethathaveanirregularextinctionpatternundercrossedpolars.Themicrostructureiscomposedofasepta(verticalcentraldarklinewithsurroundingtrabecularstructure(horizontalfibrousorbladedcrystals)anddissepiments(curvedplates).VisibleintheCKL1sampleistheradialstructureofthesepta.Onamacrostructurescale,colonialcoralshavesimilarcalcareousskeletonswithbasicskeletalelementsofaragoniteorcalcitefibers.

15)TrilobitesandOstracodes

A)Thedistinctiveshellstructureoftrilobitesistheirlongwormlikeshapedshellthatmayormaynothavehooks.Undercrossedpolars,extinctionbandssweepacrossthegrainasthestageisrotated,thisiscalledauniformprismaticextinction.Ostracodeshaveadistincteyeshapedthinshell.B)Ostracodesaredistinguishablefrombrachiopodsorbivalvesbecausetheyassmallerinsizeandhaveahomogenousprismaticwallstructurewithcalcitecementandchitincomposition.

16)Sponges

*AccordingtheDunhamclassification,PR610mostofthesampleisamicriticmudstonebutthemidlowersectionisspongeanboundstone.A)Whilenotingtherelationshipbetweenthespongesandtheothercomponentsoftherocksitisimportanttonoticehowthesparrycalcitefillsthespicules.Therealsoaremeanderingcanalstructuresandwellpreservedwallstructures.Somecanalsarepartlyfilledwithhematite.

17)BenthicForaminifers

*AccordingtoDunhamsclassification,565022isaforaminiferianpackstone.A)Characteristicsofotherfossilssuchasfragmentedshellsandskeletalfragmentsin565022,andtheabundantpelletsinAAXthatalsoindicateasemirestrictedshelflagoonenvironment..

DiageneticFeatures:19)Compaction1035TS:ChemicalCompaction:dissolutionofgrainsapparentBurl2:ChemicalCompactionsincetherearestylolitesFT88:MechanicalCompaction:grainbreakageanplasticdeformation.20)MarineCementsBAH8:Fibrousmarinecementalongroundedooliticandmicritizedgrainswithanisopachoustexture,sincethefibersarecircularandgoingallaround.ABX:Multipleisopachouslayersoffibrousmarinecementalongelongatednonsphericalgrains.TR10:columnarisopachouscementisevidentsincethelengthtowithratioisgreaterthan6:1.Theyformbladedringsaroundlargemassivecrystals.Alsosparrycalcitecementfillsvoidsandholdstherocktogether.

ABX(left)21)Beachrock**SharkBay19hasintergranularandintragranularporosity.22)MeteoricCements:VadoseCements**MiamiOolitehasthreeporositytypes,primarilyanintergranularfabricexistsbetweenooidsandalsothemeniscuscementhasintragranularporosity.Inadditionthereisaverysmallamountofmouldicporosityduetotheleachingofgrains.A)ThemeniscuscementintheMiamiOolitesampleisvadoseinorigin,evidentbythelowMgcalcitewhiskercrystalcement.Thesethin,randomlyorientatedcalcitecrystalsareproduceinthemeteoricwaters,probablyinthevadosezone.B)ThecementintheKLFIsamplealsoindicatesanorigininthevadosezoneevidentbythemicriteenvelopes,andfinelycrystallinemeniscuscement.Alsotheporesthemselvesaremoreroundedinoutlinesincethecementpreferstogrowmoreatthejunctionbetweengrains,wherewateriscaughtbycapillaryaction.Thereisalsosome,butnotmuch,evidenceofcalcitewhiskercrystalcementaswell.

23)MeteoricCements:PhreaticCements,BlockyCalcite**Redalgaehasbothintergranularandintragranularcement.B)Intheredalgae16203sample,theblockycalcitecementsurroundstheredalgaeandoccursinbetweengrainsandalsomayreplacegrains.C)InFT88,theblockcementwasnotinplacewhenthecompactionoccurred,evidentbythefactthatthecementisnotbroken.However,cementationmustofoccurearlyandnottoolongaftercompactionforthesampletobepreservelikeso.24)MeteoriticCementsInclusionfreeCrinodfragmentscanbedistinguishedfromsyntaxialovergrowthseventhoughsyntaxialovergrowthsarecementthattakesonthesamecrystalorientationofthecrinodfragmentgrainthatitisgrowing.Thesyntaxialovergrowthsaremoremassiveandcontinuousthanthecrinoids.Also,theboundariesareevidentwhenthestageisrotatedwithcrossedpolars.BothsyntaxialovergrowthsandCrinodfragmenthaveunit(singlecrystal)extinctionthatwilloccursimultaneouslymakingthegrainseemtobeonewholegrainwhileextinct.However,inwhenrotatedoutofextinctiontheboundariesbetweencrinodfragmentandthesyntaxialovergrowthsurroundingitareclear.25)CementStratigraphy:SeeDiagrambelow:

26)NeomorphicFabricsA)Petrographicfeaturesthatdifferentiateneomorphiccalcitefromblockycalcitecementbecauseneomorphicsparhaveirregularembayedtocurvedintercrystallineboundaries,contrastingwiththecommonlyplanarintercrystallineboundariesofblockycement,andneomorphicsparalsohasandirregularcrystalsizedistributionandpatchydevelopment.Gradationalandirregularboundariestotheareasofneomorphicsparandthepresenceofskeletalandothergrainsfloatingincoarsespar,alsoofferameansoftellingonefromtheother.27)Dolomite

**SR118hasthreeporositytypes,intercrystalline,mouldicarevisibleinthinsectionandfenestralinthehandsampleA)SW27HighdegreeofobliterationB)SR118Mediumdegreeofobliteration,originalfabricoffossilscompletelygone,butgeometryoforiginalcementthatsupportedgrainsisstillevident.C)B037HighdegreeofobliterationD)P10,notehighdegreeoffabricretentionE)GibsonTS:Highdegreeofobliteration

LookahappyfaceintheDolomite!!!

CarbonateLabBy

GloriaGill