Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
EOSC221
CARBONATEROCKS
1
• Limestones– OverallMineralogy– Precipita@onofCalcite– Geographicaldistribu@on– Limestonecomponents– LimestoneClassifica@on– Deposi@onalEnvironments
• Terrestrial• Marine
• Dolostones
2
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
3
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
4
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
5
• Calcitecanalsobedepositedinorganically• Thetypeofcalcitedepositedwillvaryover@medependingonocean
chemistry• “CalciteandAragoniteseas”
hIp://en.wikipedia.org/wiki/File:CalciteAragonite.jpg
6
• Calciteseas:Highspreadingratesandgreenhousecondi@ons• Highspreadingrates:morecyclingofseawaterthroughcrust
removingMgbyforma@onofMgrichclays• Highspreadingrates:increasedvolcanism=moreCO2=greenhouse
hIp://en.wikipedia.org/wiki/File:[email protected]
7
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
8
1) Ac@vityoflivingorganisms2) Precipita@onDECREASESwithincreasedpressure3) Precipita@onINCREASESwithincreasedtemperture4) Increasedwateragita@onINCREASESprecipita@on.
ImportantFactorsinPrecipita@onofCalciumCarbonate:
9
hIp://en.wikipedia.org/wiki/File:FangoCarb1.jpg
carbonatemuddeposi@oninFloridaBaylagoon.Thepresenceofyoungmangroveshelpingtoentrapthecarbonatemud.
Geographicaldistribu9onofcarbonatesediments- TheCarbonateCompensa@onDepth(CCD)- Carbonatedeposi@onasafactorofwaterdepth
10
CaCO3dissolvesbelowtheCCDunlesscoveredbyothersediments
- Distribu@onofmarinecarbonatedeposi@onwillbeeffectedbythevariousfactorsdiscussed:biology/temperature/waterdepth(pressure)/wateragita@on
TextBook
11
- Asitwillforthepast……….
LateCretaceousTextBook
12
- 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
13
Limestonecomponents• 1.Allochems:equivalentofgrainsinclas@crocks• 2.Inters@@almaterial(micriteandcement):equivalenttoclayand
cementinclas@cs
hIp://www.earth.ox.ac.uk/~oesis/micro/index.html
14
• 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
15
Drafted by Waite 99, after James 1984) hIp://sepmstrata.org/index.html
16
• ii.Allochem:NonSkeletalGrains.a.CoatedGrains:Ooids– Inorganicallyprecipitatedsmall(<2mm)sedimentarygrains
hIp://en.wikipedia.org/wiki/File:JoultersCayOoids.jpg
17
– Seriesofconcentriclayersaroundanucleus– Precipitatewhensatura@onofCaCO3increases:agita@onand/orwarming– Canforminbothmarineandlacustrinesepngs
hIp://upload.wikimedia.org/wikipedia/commons/7/76/CarmelOoids.jpg
18
b.CoatedGrains:Oncoids(Oncoliths)– Organicallyprecipitatedconcentricallyaroundanucleus– Cyanobabteria(photosynthe@c)– Warmwaterswithinthepho@czone
hIp://en.wikipedia.org/wiki/File:Oncolites.jpg
PropertyofAuthor
19
c.Peloids– Sand–siltgrade,nointernaldetail,oZenelip@cal– Probablyfecalpellets
hIp://en.wikipedia.org/wiki/File:PeloidsCarboniferousNV.jpg
20
d.Intraclasts– Piecesofintraforma@onal
material(oZencarbonatemudorfragmentsoflimestone)
– Commoninlimestonesduetotherapidcementa@onofcarbonates
e.Clas@ccomponents– QuartzClays,rock
fragments.
– Mustcollec@velybe<50%oftherock
ProprtyofAuthor
21
• 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
22
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
23
LimestoneClassifica9on• 1.FOLKCLASSIFICATION
SCHEME
• emphasisonthedetailedcomposi@onofgrainsandinters@@al(matrix)material
• Name=allochemnamecombinedwithinters@@alname(micriteorspar)
*1
24
• 2.DUNHAMCLASSIFICATIONSCHEME• TheDunhamschemefocusesondeposi@onaltextures.• Weregrainsoriginallyinmutualcontact(self-suppor@ng)or
characterizedbythepresenceofframebuildersandalgalmats?
hIp://sepmstrata.org/CarbonatePar@cles/pages/[email protected]
s
25
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.
hIp://csmres.jmu.edu/geollab/fichter/SedRx/carbdepoenvir.html
28
• i.NearshoreEnvironment– IntermiIentlycoveredwithwater,weekcurrents,somewaveac@on.– Micrites.Pelmicrites–some@meswithfenestrae– Stromatolites/algalmatescommon+/-bioturba@on– Penecontemporaneousdolomi@za@on
hIp://csmres.jmu.edu/geollab/fichter/SedRx/carbdepoenvir.html
29
Tidalflatdeposit,TansillForma@on,NewMexico
Fenestrae
Mucracks
Storm“lags”
30
• ii.Lagoons/RestrictedBays– SUB@dal– Behindbarriers/quietwaters– Wackstones/Bio-pelmicrites– Salinitycanvaryandfaunarestricted:stromatolitesmaybepresent
hIp://csmres.jmu.edu/geollab/fichter/SedRx/carbdepoenvir.html
31
• iii.Inter:dalSub:dalShoalAreas– Agitatedwater– Carbonatesands/ooids– Bio-oo-pelsparites/grainstones– Crossbeddingcommon
hIp://csmres.jmu.edu/geollab/fichter/SedRx/carbdepoenvir.html
32
BiminiBahamasNotecross-beddedcharacter
OoidShoalsNJoutlersCayBahamashIp://sepmstrata.org/index.html
33
• iv.OpenShelvesandPlaOorms–Oceanwardofbarriershoal– Grainstonesclosertoshoreline–passingintowackstonesandbiomicrites
ocean-ward– Possiblethinshelllagandstormdeposits– Bioturba@oncommon– Possiblepatchreefs
hIp://csmres.jmu.edu/geollab/fichter/SedRx/carbdepoenvir.html
34
hIp://csmres.jmu.edu/geollab/fichter/SedRx/carbdepoenvir.html
35
• 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
36
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
37
– 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
38
• vi.StarvedBasins– Pelagicbasins– Noclas@cinput– OZenbelowdepthatwhichbenthic(boIomdwelling)organismslive– Depthofsedimenta@oncontrolledbyCCD
hIp://csmres.jmu.edu/geollab/fichter/SedRx/carbdepoenvir.html
39
hIp://upload.wikimedia.org/wikipedia/commons/4/48/Coccolithophore_bloom.jpg
hIp://en.wikipedia.org/wiki/File:Gephyrocapsa_oceanica_color.jpgCoccolithbloom
coccolith
40
– 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
41
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
42
- 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”
44
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
45
TERMS / NAMES DEFINITION
46