EOSC221 - University of British Columbia · LIMESTONES Overall Mineralogy i. ARAGONITE – a...

EOSC221

CARBONATEROCKS

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•  Limestones–  OverallMineralogy–  Precipita@onofCalcite–  Geographicaldistribu@on–  Limestonecomponents–  LimestoneClassifica@on–  Deposi@onalEnvironments

•  Terrestrial•  Marine

•  Dolostones

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LECTUREOUTLINE

hIp://en.wikipedia.org/wiki/File:CarmelOoids.jpg

•  Limestones(CaCO3)anddolomites(CaMg(CO3)2)=15%Sed.rocks•  Limestones2–3xmoreabundantthandolomites•  CO3incarbonaterocksmostlyfromskeletonsoforganisms•  RecognizelimestoneinthefieldtheirsoZnessandreac@onwithHCL•  Dolomites–muchreducedtonoreac@on•  Carbonates–dissolvedeasily–KARSTlandscapes

INTRODUCTION

hIp://en.wikipedia.org/wiki/File:Limestone_Forma@on_In_Waitomo.jpg

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LIMESTONESOverallMineralogyi.ARAGONITE–apolymorphofcalcite….Differentcrystalsystem:(Orthorhombic):LowMgCO3(max1%)•  precipitatedbymollusksandmoderncorals•  Unstable–willaltertocalciteover@me

hIp://en.wikipedia.org/wiki/File:Aragonite_Salsigne_France.jpg hIp://en.wikipedia.org/wiki/File:Ammoniteplit.jpg

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ii.CALCITE(Trigonal):•  Twoforms:

–  A)LowMgCalcite<4%MgCO3–  B)HighMgCalcite>4%MgCO3

•  LowMgCalcitemorestable•  Calcitesecre@ngorganismsinclude:

brachiopods,trilobites,echinoderms

hIp://en.wikipedia.org/wiki/File:Calcite-183615.jpg hIp://en.wikipedia.org/wiki/File:Trilobitegrowth.jpg

hIp://en.wikipedia.org/wiki/File:PlatystrophiaOrdovician.jpg

brachiopod

Trilobites

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•  Calcitecanalsobedepositedinorganically•  Thetypeofcalcitedepositedwillvaryover@medependingonocean

chemistry•  “CalciteandAragoniteseas”

hIp://en.wikipedia.org/wiki/File:CalciteAragonite.jpg

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•  Calciteseas:Highspreadingratesandgreenhousecondi@ons•  Highspreadingrates:morecyclingofseawaterthroughcrust

removingMgbyforma@onofMgrichclays•  Highspreadingrates:increasedvolcanism=moreCO2=greenhouse

hIp://en.wikipedia.org/wiki/File:[email protected]

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Precipita9onofCalcite•  CO2+H2O<->H2CO3CarbonDioxideandWater<->CarbonicAcid•  H2CO3<->H++HCO3

-

Carbonicaciddissociatedintohydrogenionsandbicarbonate

•  HCO3-<->H++CO3

2-

Furtherdissocia:onofbicarbonateintohydrogenionsandcarbonate•  Ca2++CO3

2-<->CaCO3CalciumandCarbonateionsinsolu:onreacttoformCalcite/Aragonite

hIp://www.physicalgeography.net/about.html

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1)  Ac@vityoflivingorganisms2)  Precipita@onDECREASESwithincreasedpressure3)  Precipita@onINCREASESwithincreasedtemperture4)  Increasedwateragita@onINCREASESprecipita@on.

ImportantFactorsinPrecipita@onofCalciumCarbonate:

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hIp://en.wikipedia.org/wiki/File:FangoCarb1.jpg

carbonatemuddeposi@oninFloridaBaylagoon.Thepresenceofyoungmangroveshelpingtoentrapthecarbonatemud.

Geographicaldistribu9onofcarbonatesediments-  TheCarbonateCompensa@onDepth(CCD)-  Carbonatedeposi@onasafactorofwaterdepth

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CaCO3dissolvesbelowtheCCDunlesscoveredbyothersediments

-  Distribu@onofmarinecarbonatedeposi@onwillbeeffectedbythevariousfactorsdiscussed:biology/temperature/waterdepth(pressure)/wateragita@on

TextBook

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-  Asitwillforthepast……….

LateCretaceousTextBook

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-  Limestonedistribu@onthrough@me:-  ShallowMarine–LateProterozoictoModern-  DeepMarine–RareinAncient&morecommoninModern-  CaveTraver@neandSpringTufa–bothAncient&Modern-  Lakes–AncienttoModern

hIp://en.wikipedia.org/wiki/CavehIp://sepmstrata.org/CarbonatePar@cles/pages/004-Bahamas-Andros-Exumas-%26-Togo.html

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Limestonecomponents•  1.Allochems:equivalentofgrainsinclas@crocks•  2.Inters@@almaterial(micriteandcement):equivalenttoclayand

cementinclas@cs

hIp://www.earth.ox.ac.uk/~oesis/micro/index.html

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•  4majorcomponents:

•  i.Allochem:SkeletalGrains..EG:–  Bivalvesandothermollusks–  Brachiopods–  Echinodermsincludingcrinoids–  Coralsandsponges(egstromatoporoids)–  Calcitesecre@ngalgae

hIp://en.wikipedia.org/wiki/File:Crinoids_iowa_330m.jpg

hIp://en.wikipedia.org/wiki/File:AnadaraPliocene.jpg hIp://en.wikipedia.org/wiki/File:Syringoporid.jpg

Crinoids

Bivalve(clam) Coral

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Drafted by Waite 99, after James 1984) hIp://sepmstrata.org/index.html

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•  ii.Allochem:NonSkeletalGrains.a.CoatedGrains:Ooids–  Inorganicallyprecipitatedsmall(<2mm)sedimentarygrains

hIp://en.wikipedia.org/wiki/File:JoultersCayOoids.jpg

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–  Seriesofconcentriclayersaroundanucleus–  Precipitatewhensatura@onofCaCO3increases:agita@onand/orwarming–  Canforminbothmarineandlacustrinesepngs

hIp://upload.wikimedia.org/wikipedia/commons/7/76/CarmelOoids.jpg

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b.CoatedGrains:Oncoids(Oncoliths)–  Organicallyprecipitatedconcentricallyaroundanucleus–  Cyanobabteria(photosynthe@c)–  Warmwaterswithinthepho@czone

hIp://en.wikipedia.org/wiki/File:Oncolites.jpg

PropertyofAuthor

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c.Peloids–  Sand–siltgrade,nointernaldetail,oZenelip@cal–  Probablyfecalpellets

hIp://en.wikipedia.org/wiki/File:PeloidsCarboniferousNV.jpg

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d.Intraclasts–  Piecesofintraforma@onal

material(oZencarbonatemudorfragmentsoflimestone)

–  Commoninlimestonesduetotherapidcementa@onofcarbonates

e.Clas@ccomponents–  QuartzClays,rock

fragments.

–  Mustcollec@velybe<50%oftherock

ProprtyofAuthor

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•  iii.Matrix(Inters@@almaterial)a.Micrite–  Calciumcarbonatemud<4um–  Canformfromdirectprecipita@onfromCaCO3supersaturatedseawaterof

fromorganisms,par@cularlyalgae–  Generallyindica@veofquietmarinesepngs

hIp://www.sepmstrata.org/CarbonatePar@cles/pages/120-Trilobites.html

Trilobitefragment

micrite

hIp://www.sepmstrata.org/CarbonatePar@cles/pages/024-Micrite-%26-Sponge-Spic-Ghosts.html

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b.Sparite–  Calciumcarbonatecement–fillsoriginalvoidspaces–  Canbeeithercalciteordolomite–  Micritematrixcanberecrystallizedintosparite

sparite

hIp://www.earth.ox.ac.uk/~oesis/micro/medium/limestone-xpl_pm14-09.jpg

•  Pleasemakeaddi@onalnotesonGrainsandMatrix:page283-287

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LimestoneClassifica9on•  1.FOLKCLASSIFICATION

SCHEME

•  emphasisonthedetailedcomposi@onofgrainsandinters@@al(matrix)material

•  Name=allochemnamecombinedwithinters@@alname(micriteorspar)

*1

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•  2.DUNHAMCLASSIFICATIONSCHEME•  TheDunhamschemefocusesondeposi@onaltextures.•  Weregrainsoriginallyinmutualcontact(self-suppor@ng)or

characterizedbythepresenceofframebuildersandalgalmats?

hIp://sepmstrata.org/CarbonatePar@cles/pages/[email protected]

s

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LimestoneDeposi9onalEnvironments•  BothterrestrialandMarine•  Manydifferentsepngs–styleandcharacterofthesesepngsisquite

variableinbothspaceAND@me

hIp://csmres.jmu.edu/geollab/fichter/SedRx/carbdepoenvir.html

BahamaBanks26

TERRESTRIALCARBONATEDEPOSITIONALENVIRONMENTS•  Includescaliche(concentra@onsofCaCO3insoilhorizonsinarid

condi@onsbyevapora@veleaching),caveprecipitatesandlacustrineenvironments

•  Deposi:oninlakes–  i.Inorganiclimestones:mostlymicrites(limemuds)–  ii.Algalcarbonates:-stromatolitesmaybepresent–  iii.Ooidandskeletalsands

www.fossilmuseum.net

StromatolitesfromtheEoceneGreenRiverForma@on 27

MARINECARBONATEDEPOSITIONALENVIRONENTS•  Generalizedcrosssec@onthroughsomeoftheprincipleenvironmentsof

deposi@onoflimestone.•  NOTE:thisisageneralizedmodel.Noteveryareaoflimestonedeposi@on

necessarilyhastoincludeallthesefeatures.


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•  i.NearshoreEnvironment–  IntermiIentlycoveredwithwater,weekcurrents,somewaveac@on.–  Micrites.Pelmicrites–some@meswithfenestrae–  Stromatolites/algalmatescommon+/-bioturba@on–  Penecontemporaneousdolomi@za@on


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Tidalflatdeposit,TansillForma@on,NewMexico

Fenestrae

Mucracks

Storm“lags”

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•  ii.Lagoons/RestrictedBays–  SUB@dal–  Behindbarriers/quietwaters–  Wackstones/Bio-pelmicrites–  Salinitycanvaryandfaunarestricted:stromatolitesmaybepresent


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•  iii.Inter:dalSub:dalShoalAreas–  Agitatedwater–  Carbonatesands/ooids–  Bio-oo-pelsparites/grainstones–  Crossbeddingcommon


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BiminiBahamasNotecross-beddedcharacter

OoidShoalsNJoutlersCayBahamashIp://sepmstrata.org/index.html

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•  iv.OpenShelvesandPlaOorms–Oceanwardofbarriershoal–  Grainstonesclosertoshoreline–passingintowackstonesandbiomicrites

ocean-ward–  Possiblethinshelllagandstormdeposits–  Bioturba@oncommon–  Possiblepatchreefs


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•  v.Reefsystems–  Havetopographicrelief,waveresistantstructures–  Manydifferentreefproducingorganisms–  Reefrocks=biolithites/boundstones…organically“bound”together–  Cavi@escommonfilledwithskeletaldebris/cement–  Commonpetroleumreservoirs–  Infrontofreef(fore-reef):Bioclas@cmaterialbrokenoffthereef

–  Coralreefgrowthop@mum:

–  25°Cwater–  Lowclas@c/nutrientinput–  Marinestandardsalinity–  Intensewaveac@on

hIp://upload.wikimedia.org/wikipedia/commons/7/76/Blue_Linckia_Starfish.JPG

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hIp://en.wikipedia.org/wiki/File:Coral_reef_diagram.jpg hIp://en.wikipedia.org/wiki/File:Coral_reef_PloS.jpg

Backreef

–  Reefstructure:

–  1.ForeReef&reefcrest:steepslope,possiblecarbonateturbidites–  2.ReefFlat(innerreef):1–2mwaterdepth.Extensivecoraldevelopment–  3.BackReef:Reefdebrisadjacenttobackreef

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–  ElCapitanReefSystem–  MajorPermianReef

system–  Depositedinthe

DelawareBasin

hIp://www.nps.gov/gumo/naturescience/[email protected]

Pecos RiverRio G rande

GuadalupeMountainsNational Park

Carlsbad CavernsNational Park

0 50 Kilometers

50 Miles0

ApacheMountains(exposed reef)

GuadalupeMountains(exposed reef)

GlassMountains(exposed reef)

NEW MEXICOTEXAS

UNITED STATES

MEXICO

El Paso

Dell City

Alpine

Van Horn

Carlsbad

buried reef

hIp://en.wikipedia.org/wiki/File:El_Capitan_2005.jpg

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•  vi.StarvedBasins–  Pelagicbasins–  Noclas@cinput–  OZenbelowdepthatwhichbenthic(boIomdwelling)organismslive–  Depthofsedimenta@oncontrolledbyCCD


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hIp://upload.wikimedia.org/wikipedia/commons/4/48/Coccolithophore_bloom.jpg

hIp://en.wikipedia.org/wiki/File:Gephyrocapsa_oceanica_color.jpgCoccolithbloom

coccolith

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–  AncientpelagiclimestonescanbeVERYextensive–  CretaceouschalkseasofNWEurope,SEUSA:coccoliths

hIp://upload.wikimedia.org/wikipedia/commons/7/7e/White_cliffs_of_dover_09_2004.jpg hIp://jan.ucc.nau.edu/~rcb7/090Marect.jpg

CretaceousChalkSeasWhiteCliffsofDover

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DOLOSTONES-  CaMg(CO3)2Mgsubsi@tu@ngCaTrigonal-rhombohedralsystem-  DoesNOTdissolverapidlyinHCL-  Feinthecrystalstructurecangivedolomiteayellow–brown

colour,ahighMncontentproducesarose@nt.

hIp://en.wikipedia.org/wiki/File:Dolomit,_Rumunia;_pseudomorfoza_po_kalcycie.jpg

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-  Primarilyformsunderdiagene@cprocessesbythealtera@onoflimestone-Willdealwithitmoreinthenextlesson

-  Limestonethathasbeenalteredtodolomitewillloosemanyofthestructures/texturesoftheoriginalsediment.

-  “Ghost”texturesmayremain

hIp://www.earth.ox.ac.uk/~oesis/micro/medium/limestone-dolomi@c_pm20-11.jpg

Fieldofview3.5mm. 43

Classifica9onofDolomites-  UsetheFolkandDunhamclassifica@onschemeprocededbythe

worddolomi@corprefixedby“dolo”-  EG:dolomicrite/dolobiosparite

“dolo” “dolo” “dolo” “dolo”

“dolo”

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GLOSSARY All lecture material is potentially examinable. Is up to you to know unfamiliar terms / names / people. Use this space to create your own lecture glossary

TERMS / NAMES DEFINITION

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TERMS / NAMES DEFINITION

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EOSC221 - University of British Columbia · LIMESTONES Overall Mineralogy i. ARAGONITE – a...

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