Carbonate GrainsCarbonate Grains

Carbaonate vs Clastic RksCarbaonate vs Clastic Rks

Clastic rocks form from fragments of Clastic rocks form from fragments of pre-existing rockspre-existing rocks Form outside the basinForm outside the basin

Carbonate rocks form through Carbonate rocks form through biochemical processesbiochemical processes Form within the basinForm within the basin Depends on chemistry of waterDepends on chemistry of water And temperature of waterAnd temperature of water And biological activityAnd biological activity

IntroductionIntroduction

Carbonate rocks Occur from Cambrian Carbonate rocks Occur from Cambrian onon PreC mostly dolomite w/ algae/stromatolite PreC mostly dolomite w/ algae/stromatolite Past deposition= epeiric seas Past deposition= epeiric seas Economically importantEconomically important Good for environmental interpretationsGood for environmental interpretations Form in basin of depositionForm in basin of deposition Skeletal grains in rks depend on ageSkeletal grains in rks depend on age

Controls on Carbonate DepositionControls on Carbonate Deposition

Carbonate Depositon controlled by:Carbonate Depositon controlled by: Shell producing organisms require warm watersShell producing organisms require warm waters

most COmost CO33 seds in trop-subtrop belt (30-40N&S) seds in trop-subtrop belt (30-40N&S) SSoo/oo--require normal salinities/oo--require normal salinities Water depth--shallow photic zone, agitated, deeper=CCDWater depth--shallow photic zone, agitated, deeper=CCD

siliclastic imput--dilute accumulating CO3 sedsiliclastic imput--dilute accumulating CO3 sed

MineralogyMineralogy MINERALOGYMINERALOGY

recent & subrecent = 2 recent & subrecent = 2 COCO33 minerals minerals predominatepredominate

aragonite aragonite (orthorhombic) low Mg(orthorhombic) low Mg

calcite (trigonal)calcite (trigonal) mineralogy depends on mineralogy depends on

grainsgrains Organism = specific Organism = specific

mineralogy or mixturemineralogy or mixture Mg content in part Mg content in part

depends on water tempdepends on water temp Non-CONon-CO33 mineral in LS mineral in LS

terrigenous quartz & terrigenous quartz & clayclay

pyritepyrite hematitehematite chert & phosphate of chert & phosphate of

diagenetic origindiagenetic origin

pengellytrust.org

Non-skeletal Non-skeletal grains --Ooidsgrains --Ooids Spherical-concentric Spherical-concentric

lamellae around nucleuslamellae around nucleus Nucleus=CONucleus=CO33 particle or particle or

qtz grainqtz grain Sed composed of Sed composed of

ooids=ooliteooids=oolite < 2mm diam; < 2mm diam;

Pisolite=>2mmPisolite=>2mm Water depth generally Water depth generally

<5m, may reach 10-15m<5m, may reach 10-15m Composite ooid=>1 ooid Composite ooid=>1 ooid

enveloped by lamellaenveloped by lamella Most aragonitic, may get Most aragonitic, may get

high Mg or arag/Hi Mghigh Mg or arag/Hi Mg Ancient ooids=lowMg, Ancient ooids=lowMg,

unless silicified or unless silicified or dolomitizeddolomitized

www.nhm.ac.uk/hosted_sites/quekett/island.html

Ooid Place of FormationOoid Place of Formation

Lakes, lagoons, rivers, Lakes, lagoons, rivers, tidal flats, fresh & tidal flats, fresh & hypersaline watershypersaline waters

Some ooids micritic--Some ooids micritic--endolithic algaeendolithic algae

Shallow tropical Shallow tropical supersaturated watersupersaturated water

Saturation, agitation, Saturation, agitation, elevated temp, then elevated temp, then prec on prec on nucleinuclei

031 Joulters Cay Ooids Offshore Bahamas, note Batophera algae clumps (Kendall Photo)

1 Bahamas Ooids

Non skeletal Non skeletal grains--Pisolitesgrains--Pisolites

Greater than 2 Greater than 2 mm in sizemm in size

Pisolites

Non skeletal grains –Non skeletal grains –PeloidsPeloids

Spherical, cylindrical of microxlln Spherical, cylindrical of microxlln COCO33-- no internal structure-- no internal structure

Mostly .1-.5 mm –mostly fecal Mostly .1-.5 mm –mostly fecal pelletspellets

Common in ls and micritic l.sCommon in ls and micritic l.s

IntraclastsIntraclasts CO3 rip-ups lithified or partially lithified CO3 rip-ups lithified or partially lithified

sedimentsediment

SKELETAL GRAINSSKELETAL GRAINS

skeletal components controlled by skeletal components controlled by invertebrates through time & spaceinvertebrates through time & space

controlling environmental factors:controlling environmental factors: depthdepth temptemp S o/ooS o/oo substratesubstrate turbulenceturbulence

I.D. skeletal grainsI.D. skeletal grains

Shape/sizeShape/size Internal microstructure--diagenesis Internal microstructure--diagenesis

may destroymay destroy MineralogyMineralogy Spines or sporesSpines or spores

MolluscaMollusca Mollusca (bivalves, Mollusca (bivalves,

gastropods, cephalopod, gastropods, cephalopod, found lower Paleozoic found lower Paleozoic onward)onward) BivalvesBivalves

marine, fresh, marine, fresh, brackish watersbrackish waters

import since Tert import since Tert w/decline of brachsw/decline of brachs

mode of lifemode of life infuanal-in sedsinfuanal-in seds epifauanal-epifauanal-

attached to attached to substratesubstrate

vagil—crawlervagil—crawler calcite bivalves calcite bivalves

will retain will retain structurestructure

GastropodsGastropods

Common in Common in shallow shallow marinemarine

Vast numbersVast numbers Hypersaline, Hypersaline,

brackish--brackish--tolerate tolerate fluctuations fluctuations and salinity and salinity extremesextremes

Most benthic Most benthic & vagile& vagile

Look to i.d. by Look to i.d. by shapeshape

ClamsClams

CephalopodsCephalopods Nautiloids, aminoid, Paleoz Nautiloids, aminoid, Paleoz & Meso, belemnoids in Meso & Meso, belemnoids in Meso l.s.l.s. nektonic or nektonic-planktonicnektonic or nektonic-planktonic common pelagic, deep water common pelagic, deep water

l.s.l.s. shell orig. arag--lose internal shell orig. arag--lose internal

stucturestucture large size, presence of speta & large size, presence of speta &

siphuncle-keyssiphuncle-keys

BrachiopodsBrachiopods Common Paleozoic Common Paleozoic

& Mesozoic, less so & Mesozoic, less so todaytoday

shallow marineshallow marine now not prominent now not prominent

marine marine invertebrate similar invertebrate similar to bivavles but low to bivavles but low to high Mg calcite,to high Mg calcite,

internal structure internal structure typically preserved typically preserved structurestructure

blackriverfossils.org

Cnidaria (especially corals)Cnidaria (especially corals)

include Anthozoa (corals)include Anthozoa (corals) 2 types corals2 types corals::

hermatypic-contain symbiotic dinoflagellate algae (zooanthellae) in polypshermatypic-contain symbiotic dinoflagellate algae (zooanthellae) in polyps ahermatypic--do not contain symbiotic dinoflagellateahermatypic--do not contain symbiotic dinoflagellate because of algae, hermatypic must be in shallow warm & clear waterbecause of algae, hermatypic must be in shallow warm & clear water hermatypic corals are reef-formershermatypic corals are reef-formers ahermatypic corals may occur at great depth & tolerate colder water, localahermatypic corals may occur at great depth & tolerate colder water, local

Paleozoic: Rugose & tabular corals= hi mg calcite-structure preservedPaleozoic: Rugose & tabular corals= hi mg calcite-structure preserved scelractinian corals (Triassic-Rec) aragonite skeleton: poorly preserved scelractinian corals (Triassic-Rec) aragonite skeleton: poorly preserved

structurestructure

mesa.edu.au

CoralsCorals

palaeos.com

humboldt.edu

Tabulate

Rugose

Sceleractinian science.uva.nl

EchinodermataEchinodermata All marine, echinoids All marine, echinoids

(sea urchins) crinoids (sea urchins) crinoids (sea lillies)(sea lillies)

Echinoids found in reef Echinoids found in reef & assoc, environ.& assoc, environ.

Crinoids in deep Crinoids in deep water, not much sed. water, not much sed. contrib.contrib.

Paleo & Meso crinoids Paleo & Meso crinoids major componentmajor component

Identified by large Identified by large single calcite xlssingle calcite xls

May find echinoderm May find echinoderm spinesspines

science.jrank.org

BryzoaBryzoaSmall colonial marine organismSmall colonial marine organism In past, helped form reef & In past, helped form reef &

other l.s esp in Paleozoicother l.s esp in Paleozoic Formed of string of cells Formed of string of cells

(zooecia about 100 u in diam, (zooecia about 100 u in diam, joined by stem of calcitejoined by stem of calcite

ForaminiferaForaminifera

Composed of lo Mg calcite, rarely aragComposed of lo Mg calcite, rarely arag Planktonic & benthic, planktonic dominatePlanktonic & benthic, planktonic dominate Many forms, but in l.s most circular to Many forms, but in l.s most circular to

subcircular subcircular

AlgaeAlgae

major contrib. to major contrib. to carb. sedscarb. seds

provide skeletal provide skeletal grains, trap sed to grains, trap sed to form laminated form laminated seds, break down seds, break down particles by boring particles by boring into theminto them

many PreC carb. many PreC carb. formed in part by formed in part by algaealgae

wetwebmedia.com

Algae ContinuedAlgae Continued 4 major types of 4 major types of

algaealgae red algae red algae

(rhodophyta)(rhodophyta) green algae green algae

(chlorphyta)(chlorphyta) blue-grn algae blue-grn algae

(cyanophyta-bore (cyanophyta-bore into skeletal grain)into skeletal grain)

yellow green yellow green algae algae (chrysophyta-(chrysophyta-coccoliths)coccoliths)

Algae ContinuedAlgae Continued Bluegreen algae & algal matsBluegreen algae & algal mats

occur in lo lat. shallow subtidal occur in lo lat. shallow subtidal through supratidal environments through supratidal environments (just above high tide)(just above high tide)

also occur in hypersaline lakes and also occur in hypersaline lakes and marshesmarshes

bl grn is mucilagiinous & bl grn is mucilagiinous & filamentous—trap particles to form filamentous—trap particles to form stromatolitestromatolite

stromatolite occur through out but stromatolite occur through out but are especially important in the are especially important in the PreCPreC

stromatolite=variety of growth stromatolite=variety of growth patternspatterns

morphologies depend on water morphologies depend on water depth, tidal & wave energy, sed depth, tidal & wave energy, sed rate, & frequency of exposurerate, & frequency of exposure

small columns & dome in less small columns & dome in less agitated bay watersagitated bay waters

low domes & planar mats in low domes & planar mats in protected tidal flatsprotected tidal flats

AlgaeFrom capping reef deposits of the w:Tabernas basin, Spain

Stromatolites & Stromatolites & OncalitesOncalites

Algae ContinuedAlgae Continued

endolithic alage-endolithic alage-borersborers fine micrite due fine micrite due

to endolithic to endolithic algae then dep. algae then dep. at depths of 100-at depths of 100-200 m= photic 200 m= photic zone--zone--

Most of the microalgal borers associated with corals are chlorophyes of the genus Ostreobium as shown below (white arrow). The red arrows indicate borings from endolithic worms or mussels to be discussed later. www2.fiu.edu

Other CO3-forming organismsOther CO3-forming organisms

sponges: spicules may be silicasponges: spicules may be silica arthropodsarthropods

ostracods 1mm, Cam-recentostracods 1mm, Cam-recent shallow marine, brakish or fresh envshallow marine, brakish or fresh env shell=calcite shell=calcite

trilobite-Cam-Permtrilobite-Cam-Perm entirely marineentirely marine

MicriteMicrite F gr dark matrix of carb called F gr dark matrix of carb called

micrite < 4 umicrite < 4 u accumulates in tidal flats, accumulates in tidal flats,

shallow lagoons to deep ocean shallow lagoons to deep ocean floor and on slopesfloor and on slopes thought to accumulate through thought to accumulate through

breakdown of blgrn algaebreakdown of blgrn algae algae breaks down and release algae breaks down and release

vast arag needlesvast arag needles other processesother processes::

bioerosion-boring algae & bioerosion-boring algae & spongessponges

mechanical breakdown of skeletal mechanical breakdown of skeletal grains-waves/currentsgrains-waves/currents

biochemical precip--biochemical precip--photosynthesis & photosynthesis & decompositiondecomposition

geology.sfasu.edu

atlantisonline.smfforfree2.com

Aragonite NeedlesAragonite Needles

AAPG

Micrite ContinuedMicrite Continued

inorganic precipitation in some areas inorganic precipitation in some areas e.g. Arabian coast due to e.g. Arabian coast due to supersaturated water--little supersaturated water--little calcareous algae is presentcalcareous algae is present

cannot discount inorganic precipt in cannot discount inorganic precipt in pastpast

also, micrite may be a cementalso, micrite may be a cement

Carbonate RocksCarbonate Rocks

Carbonate rocks - limestones Carbonate rocks - limestones composed of calcite (CaCO3) or composed of calcite (CaCO3) or dolostones composed of dolomite dolostones composed of dolomite (CaMgCO3). (CaMgCO3).

Form through biological and Form through biological and biochemical processes and through biochemical processes and through inorganic precipitation from seawater inorganic precipitation from seawater

Carbonate rocks widespread and in Carbonate rocks widespread and in every geological period beginning every geological period beginning with Cambrian with Cambrian

EnvironmentEnvironment Most carbonate sediments Most carbonate sediments

form in warm waters form in warm waters E.g., corals and algae E.g., corals and algae

common in carbonate rocks, common in carbonate rocks, and mostly found tropical to and mostly found tropical to subtropical latitudes or from subtropical latitudes or from about 30about 30oo N and S latitudes N and S latitudes

Most carbonate sediments Most carbonate sediments generated in photic zone generated in photic zone

Unlike sandstones, most Unlike sandstones, most carbonate grains formed in carbonate grains formed in environment in which they environment in which they are deposited are deposited

Detrital grains in sandstones Detrital grains in sandstones usually derived from outside usually derived from outside the environment in which the environment in which they were deposited they were deposited

Environment ContinuedEnvironment Continued Carbonate sediments Carbonate sediments

do not usually occur do not usually occur below depths of below depths of about 3500 -4000 about 3500 -4000 meters in the oceans meters in the oceans

Below these depths Below these depths carbonate sediments carbonate sediments will dissolve will dissolve

The depths at which The depths at which carbonate sediments carbonate sediments dissolve in the ocean dissolve in the ocean is called the is called the carbonate carbonate compensation depth compensation depth or CCD or CCD

Classification SchemeClassification Scheme Two principal classification schemes are used for Two principal classification schemes are used for

limestones. One is Folk's classification scheme, limestones. One is Folk's classification scheme, named after Robert Folk, and Dunham's named after Robert Folk, and Dunham's classification scheme, named after Robert classification scheme, named after Robert Dunham Dunham

Folk's scheme based on presence or absence of Folk's scheme based on presence or absence of allochems (carbonate particles or grains), matrix allochems (carbonate particles or grains), matrix (limestone clay called micrite), and type of (limestone clay called micrite), and type of cement (spar is a cement composed of coarse)cement (spar is a cement composed of coarse)

Dunham's scheme is based on texture of rock. i.e. Dunham's scheme is based on texture of rock. i.e. whether rock contains matrix, whether carbonate whether rock contains matrix, whether carbonate grains float in matrix or whether they are in grains float in matrix or whether they are in contact with each other, and whether rock has contact with each other, and whether rock has carbonate grains carbonate grains

Dunham’s ClassificationDunham’s Classification

Based on whether Based on whether have more or less that have more or less that 10% grains10% grains

Whether rock is mud Whether rock is mud or grain supported.or grain supported.

Also if original Also if original components were components were bound together like bound together like coral.coral.

Tells about transport Tells about transport history.history.

Folk ClassificationFolk Classification Carbonate rocks Carbonate rocks

consits of:consits of: Allochems—grainsAllochems—grains Intersitial material—Intersitial material—

micrite or spar cementmicrite or spar cement Micrite is "lime mud", Micrite is "lime mud",

the dense, dull-looking the dense, dull-looking sediment made of clay sediment made of clay sized crystals of sized crystals of CaCO3.CaCO3.

Spar—clear to Spar—clear to translucent carbonate translucent carbonate cement. cement.

Micrite and SparMicrite and Spar

Folk ContinuedFolk Continued

Name is built up by stringing together all the Name is built up by stringing together all the allochem names in order from least to most allochem names in order from least to most abundant, and then adding the interstitial abundant, and then adding the interstitial material name ("matrix" below for short). For material name ("matrix" below for short). For example, a rock like this:example, a rock like this:

Oolites + Fossils + Spar matrixOolites + Fossils + Spar matrix = Oo bio = Oo bio sparitesparite   The name is written as one word,    The name is written as one word, OobiospariteOobiosparite..

     Another example (again allochems from least      Another example (again allochems from least to most abundant):to most abundant):

Pellets + Oolites + Fossils + Micrite matrixPellets + Oolites + Fossils + Micrite matrix = pel oo bio micrite= pel oo bio micrite   The name is written as one word,    The name is written as one word, PeloobiomicritePeloobiomicrite..

     But what if there is both micrite and spar      But what if there is both micrite and spar matrix? The system is the same; just list them matrix? The system is the same; just list them from least to most abundant.from least to most abundant.

Fossils + Spar matrix + Micrite matrixFossils + Spar matrix + Micrite matrix = bio = bio spar micritespar micrite

Carbonate GrainsCarbonate Grains ooidsooids--Ooids are --Ooids are

spherical grains spherical grains formed by calcite formed by calcite precipitation around a precipitation around a nucleus such as a shell nucleus such as a shell fragment, a quartz fragment, a quartz grain, etc. They are grain, etc. They are less than 2mm in less than 2mm in diameter and typically diameter and typically form in shallow, warm, form in shallow, warm, agitated, and agitated, and carbonate-saturated carbonate-saturated waters such as those waters such as those near the Bahamas.near the Bahamas.

pisolitespisolites--Pisolites --Pisolites are ooids greater are ooids greater than 2mm in sizethan 2mm in size

Similar Similar environments as environments as ooidsooids

stromatolitesstromatolites--Stromatolites are --Stromatolites are laminated carbonate sediments laminated carbonate sediments composed of mats of blue-green composed of mats of blue-green algae and layers of sediment. algae and layers of sediment. The algae, which forms the mats, The algae, which forms the mats, is a plant and plants require is a plant and plants require sunlight to survive. Therefore, sunlight to survive. Therefore, stromatolites generally form in stromatolites generally form in warm shallow waters. The algae warm shallow waters. The algae is "sticky" and it grows filaments. is "sticky" and it grows filaments. This sticky and filamentous algae This sticky and filamentous algae traps sediment brought in by the traps sediment brought in by the currents. Consequently, a layer currents. Consequently, a layer of algae forms then a layer of of algae forms then a layer of sediment is deposited on top of sediment is deposited on top of the algae. Subsequently, the the algae. Subsequently, the algae grows through the sediment algae grows through the sediment to form another mat and the cycle to form another mat and the cycle begins again. Ultimately, a begins again. Ultimately, a layered rock composed of layered rock composed of alternating algal mats and alternating algal mats and sediments is produced. sediments is produced. Stromatolites form in quiet, Stromatolites form in quiet, hypersaline waters with little hypersaline waters with little animal life around to destroy the animal life around to destroy the mats.mats.

oncolitesoncolites----Oncolites are Oncolites are stromatolites stromatolites rolled in a rolled in a ball. ball.

coralscorals--Corals have a --Corals have a symbiotic relationship symbiotic relationship with dinoflagellate algae with dinoflagellate algae called zooanthellae. called zooanthellae. Algae are plants. Algae are plants. Therefore, in order for Therefore, in order for corals to survive they corals to survive they generally have to be generally have to be within the photic zone within the photic zone (the zone of maximum (the zone of maximum light penetration in the light penetration in the ocean). Plants require ocean). Plants require sunlight for sunlight for photosynthesis. In the photosynthesis. In the process of process of photosynthesis, plants photosynthesis, plants produce oxygen and produce oxygen and consume CO2. Corals are consume CO2. Corals are major reef formers today major reef formers today and in the past. and in the past. However, keep in mind However, keep in mind that some corals do occur that some corals do occur in deep waters. in deep waters.

IntraclastsIntraclasts--Semi---Semi-consolidated consolidated carbonate material carbonate material ripped-up and ripped-up and incorporated in the incorporated in the rock.rock.

dolostonedolostone--A --A dolostone is a dolostone is a rock compose of rock compose of 90-100% 90-100% dolomite.dolomite.

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