Carbonate Grains

Carbaonate vs Clastic Rks Clastic rocks form from fragments of pre- existing rocks Clastic rocks form from fragments of pre- existing rocks Form outside the basin Form outside the basin Carbonate rocks form through biochemical processes Carbonate rocks form through biochemical processes Form within the basin Form within the basin Depends on chemistry of water Depends on chemistry of water And temperature of water And temperature of water And biological activity And biological activity

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

Controls on Carbonate Deposition Carbonate Depositon controlled by: Carbonate Depositon controlled by: Shell producing organisms require warm waters Shell producing organisms require warm waters most CO 3 seds in trop-subtrop belt (30-40N&S) most CO 3 seds in trop-subtrop belt (30-40N&S) S o /oo--require normal salinities S o /oo--require normal salinities Water depth--shallow photic zone, agitated, deeper=CCD Water depth--shallow photic zone, agitated, deeper=CCD siliclastic imput--dilute accumulating CO3 sed siliclastic imput--dilute accumulating CO3 sed

Mineralogy MINERALOGY MINERALOGY recent & subrecent = 2 CO 3 minerals predominate recent & subrecent = 2 CO 3 minerals predominate aragonite (orthorhombic) low Mg aragonite (orthorhombic) low Mg calcite (trigonal) calcite (trigonal) mineralogy depends on grains mineralogy depends on grains Organism = specific mineralogy or mixture Organism = specific mineralogy or mixture Mg content in part depends on water temp Mg content in part depends on water temp Non-CO 3 mineral in LS Non-CO 3 mineral in LS terrigenous quartz & clay terrigenous quartz & clay pyrite pyrite hematite hematite chert & phosphate of diagenetic origin chert & phosphate of diagenetic origin pengellytrust.org

Non-skeletal grains --Ooids Spherical-concentric lamellae around nucleus Spherical-concentric lamellae around nucleus Nucleus=CO 3 particle or qtz grain Nucleus=CO 3 particle or qtz grain Sed composed of ooids=oolite Sed composed of ooids=oolite 2mm 2mm Water depth generally <5m, may reach 10-15m Water depth generally <5m, may reach 10-15m Composite ooid=>1 ooid enveloped by lamella Composite ooid=>1 ooid enveloped by lamella Most aragonitic, may get high Mg or arag/Hi Mg Most aragonitic, may get high Mg or arag/Hi Mg Ancient ooids=lowMg, unless silicified or dolomitized Ancient ooids=lowMg, unless silicified or dolomitized

Ooid Place of Formation Lakes, lagoons, rivers, tidal flats, fresh & hypersaline waters Lakes, lagoons, rivers, tidal flats, fresh & hypersaline waters Some ooids micritic-- endolithic algae Some ooids micritic-- endolithic algae Shallow tropical supersaturated water Shallow tropical supersaturated water Saturation, agitation, elevated temp, then prec on nuclei Saturation, agitation, elevated temp, then prec on nuclei 031 Joulters Cay Ooids Offshore Bahamas, note Batophera algae clumps (Kendall Photo) 1 Bahamas Ooids

Non skeletal grains- -Pisolites Greater than 2 mm in size Greater than 2 mm in size Pisolites

Non skeletal grains – Peloids Spherical, cylindrical of microxlln CO 3 -- no internal structure Spherical, cylindrical of microxlln CO 3 -- no internal structure Mostly.1-.5 mm –mostly fecal pellets Mostly.1-.5 mm –mostly fecal pellets Common in ls and micritic l.s Common in ls and micritic l.s

Intraclasts CO3 rip-ups lithified or partially lithified sediment CO3 rip-ups lithified or partially lithified sediment

SKELETAL GRAINS skeletal components controlled by invertebrates through time & space skeletal components controlled by invertebrates through time & space controlling environmental factors: controlling environmental factors: depth depth temp temp S o/oo S o/oo substrate substrate turbulence turbulence

I.D. skeletal grains Shape/size Shape/size Internal microstructure--diagenesis may destroy Internal microstructure--diagenesis may destroy Mineralogy Mineralogy Spines or spores Spines or spores

Mollusca Mollusca (bivalves, gastropods, cephalopod, found lower Paleozoic onward) Mollusca (bivalves, gastropods, cephalopod, found lower Paleozoic onward) Bivalves Bivalves marine, fresh, brackish waters marine, fresh, brackish waters import since Tert w/decline of brachs import since Tert w/decline of brachs mode of life mode of life infuanal-in seds infuanal-in seds epifauanal-attached to substrate epifauanal-attached to substrate vagil—crawler vagil—crawler calcite bivalves will retain structure calcite bivalves will retain structure

Gastropods Common in shallow marine Common in shallow marine Vast numbers Vast numbers Hypersaline, brackish-- tolerate fluctuations and salinity extremes Hypersaline, brackish-- tolerate fluctuations and salinity extremes Most benthic & vagile Most benthic & vagile Look to i.d. by shape Look to i.d. by shape

Clams

Cephalopods Nautiloids, aminoid, Paleoz & Meso, belemnoids in Meso l.s. Nautiloids, aminoid, Paleoz & Meso, belemnoids in Meso l.s. nektonic or nektonic-planktonic nektonic or nektonic-planktonic common pelagic, deep water l.s. common pelagic, deep water l.s. shell orig. arag--lose internal stucture shell orig. arag--lose internal stucture large size, presence of speta & siphuncle-keys large size, presence of speta & siphuncle-keys

Brachiopods Common Paleozoic & Mesozoic, less so today Common Paleozoic & Mesozoic, less so today shallow marine shallow marine now not prominent marine invertebrate similar to bivavles but low to high Mg calcite, now not prominent marine invertebrate similar to bivavles but low to high Mg calcite, internal structure typically preserved structure internal structure typically preserved structure blackriverfossils.org

Cnidaria (especially corals) include Anthozoa (corals) include Anthozoa (corals) 2 types corals : 2 types corals : hermatypic-contain symbiotic dinoflagellate algae (zooanthellae) in polyps hermatypic-contain symbiotic dinoflagellate algae (zooanthellae) in polyps ahermatypic--do not contain symbiotic dinoflagellate ahermatypic--do not contain symbiotic dinoflagellate because of algae, hermatypic must be in shallow warm & clear water because of algae, hermatypic must be in shallow warm & clear water hermatypic corals are reef-formers hermatypic corals are reef-formers ahermatypic corals may occur at great depth & tolerate colder water, local ahermatypic corals may occur at great depth & tolerate colder water, local Paleozoic: Rugose & tabular corals= hi mg calcite-structure preserved Paleozoic: Rugose & tabular corals= hi mg calcite-structure preserved scelractinian corals (Triassic-Rec) aragonite skeleton: poorly preserved structure scelractinian corals (Triassic-Rec) aragonite skeleton: poorly preserved structure mesa.edu.au

Corals palaeos.com humboldt.edu Tabulate Rugose Sceleractinian science.uva.nl

Echinodermata All marine, echinoids (sea urchins) crinoids (sea lillies) All marine, echinoids (sea urchins) crinoids (sea lillies) Echinoids found in reef & assoc, environ. Echinoids found in reef & assoc, environ. Crinoids in deep water, not much sed. contrib. Crinoids in deep water, not much sed. contrib. Paleo & Meso crinoids major component Paleo & Meso crinoids major component Identified by large single calcite xls Identified by large single calcite xls May find echinoderm spines May find echinoderm spines science.jrank.org

Bryzoa Small colonial marine organism In past, helped form reef & other l.s esp in Paleozoic In past, helped form reef & other l.s esp in Paleozoic Formed of string of cells (zooecia about 100 u in diam, joined by stem of calcite Formed of string of cells (zooecia about 100 u in diam, joined by stem of calcite

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

Algae major contrib. to carb. seds major contrib. to carb. seds provide skeletal grains, trap sed to form laminated seds, break down particles by boring into them provide skeletal grains, trap sed to form laminated seds, break down particles by boring into them many PreC carb. formed in part by algae many PreC carb. formed in part by algae wetwebmedia.com

Algae Continued 4 major types of algae 4 major types of algae red algae (rhodophyta) red algae (rhodophyta) green algae (chlorphyta) green algae (chlorphyta) blue-grn algae (cyanophyta-bore into skeletal grain) blue-grn algae (cyanophyta-bore into skeletal grain) yellow green algae (chrysophyta- coccoliths) yellow green algae (chrysophyta- coccoliths)

Algae Continued Bluegreen algae & algal mats Bluegreen algae & algal mats occur in lo lat. shallow subtidal through supratidal environments (just above high tide) occur in lo lat. shallow subtidal through supratidal environments (just above high tide) also occur in hypersaline lakes and marshes also occur in hypersaline lakes and marshes bl grn is mucilagiinous & filamentous—trap particles to form stromatolite bl grn is mucilagiinous & filamentous—trap particles to form stromatolite stromatolite occur through out but are especially important in the PreC stromatolite occur through out but are especially important in the PreC stromatolite=variety of growth patterns stromatolite=variety of growth patterns morphologies depend on water depth, tidal & wave energy, sed rate, & frequency of exposure morphologies depend on water depth, tidal & wave energy, sed rate, & frequency of exposure small columns & dome in less agitated bay waters small columns & dome in less agitated bay waters low domes & planar mats in protected tidal flats low domes & planar mats in protected tidal flats AlgaeFrom capping reef deposits of the w:Tabernas basin, Spainw:Tabernas basinSpain

Stromatolites & Oncalites

Algae Continued endolithic alage- borers endolithic alage- borers fine micrite due to endolithic algae then dep. at depths of m= photic zone-- fine micrite due to endolithic algae then dep. at depths of m= photic 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 organisms sponges: spicules may be silica sponges: spicules may be silica arthropods arthropods ostracods 1mm, Cam-recent ostracods 1mm, Cam-recent shallow marine, brakish or fresh env shallow marine, brakish or fresh env shell=calcite shell=calcite trilobite-Cam-Perm trilobite-Cam-Perm entirely marine entirely marine

Micrite F gr dark matrix of carb called micrite < 4 u F gr dark matrix of carb called micrite < 4 u accumulates in tidal flats, shallow lagoons to deep ocean floor and on slopes accumulates in tidal flats, shallow lagoons to deep ocean floor and on slopes thought to accumulate through breakdown of blgrn algae thought to accumulate through breakdown of blgrn algae algae breaks down and release vast arag needles algae breaks down and release vast arag needles other processes : other processes : bioerosion-boring algae & sponges bioerosion-boring algae & sponges mechanical breakdown of skeletal grains- waves/currents mechanical breakdown of skeletal grains- waves/currents biochemical precip-- photosynthesis & decomposition biochemical precip-- photosynthesis & decomposition geology.sfasu.edu atlantisonline.smfforfree2.com

Aragonite Needles AAPG

Micrite Continued inorganic precipitation in some areas e.g. Arabian coast due to supersaturated water--little calcareous algae is present inorganic precipitation in some areas e.g. Arabian coast due to supersaturated water--little calcareous algae is present cannot discount inorganic precipt in past cannot discount inorganic precipt in past also, micrite may be a cement also, micrite may be a cement

Carbonate Rocks Carbonate rocks - limestones composed of calcite (CaCO3) or dolostones composed of dolomite (CaMgCO3). Carbonate rocks - limestones composed of calcite (CaCO3) or dolostones composed of dolomite (CaMgCO3). Form through biological and biochemical processes and through inorganic precipitation from seawater Form through biological and biochemical processes and through inorganic precipitation from seawater Carbonate rocks widespread and in every geological period beginning with Cambrian Carbonate rocks widespread and in every geological period beginning with Cambrian

Environment Most carbonate sediments form in warm waters Most carbonate sediments form in warm waters E.g., corals and algae common in carbonate rocks, and mostly found tropical to subtropical latitudes or from about 30 o N and S latitudes E.g., corals and algae common in carbonate rocks, and mostly found tropical to subtropical latitudes or from about 30 o N and S latitudes Most carbonate sediments generated in photic zone Most carbonate sediments generated in photic zone Unlike sandstones, most carbonate grains formed in environment in which they are deposited Unlike sandstones, most carbonate grains formed in environment in which they are deposited Detrital grains in sandstones usually derived from outside the environment in which they were deposited Detrital grains in sandstones usually derived from outside the environment in which they were deposited

Environment Continued Carbonate sediments do not usually occur below depths of about meters in the oceans Carbonate sediments do not usually occur below depths of about meters in the oceans Below these depths carbonate sediments will dissolve Below these depths carbonate sediments will dissolve The depths at which carbonate sediments dissolve in the ocean is called the carbonate compensation depth or CCD The depths at which carbonate sediments dissolve in the ocean is called the carbonate compensation depth or CCD

Classification Scheme Two principal classification schemes are used for limestones. One is Folk's classification scheme, named after Robert Folk, and Dunham's classification scheme, named after Robert Dunham Two principal classification schemes are used for limestones. One is Folk's classification scheme, named after Robert Folk, and Dunham's classification scheme, named after Robert Dunham Folk's scheme based on presence or absence of allochems (carbonate particles or grains), matrix (limestone clay called micrite), and type of cement (spar is a cement composed of coarse) Folk's scheme based on presence or absence of allochems (carbonate particles or grains), matrix (limestone clay called micrite), and type of cement (spar is a cement composed of coarse) Dunham's scheme is based on texture of rock. i.e. whether rock contains matrix, whether carbonate grains float in matrix or whether they are in contact with each other, and whether rock has carbonate grains Dunham's scheme is based on texture of rock. i.e. whether rock contains matrix, whether carbonate grains float in matrix or whether they are in contact with each other, and whether rock has carbonate grains

Dunham’s Classification Based on whether have more or less that 10% grains Based on whether have more or less that 10% grains Whether rock is mud or grain supported. Whether rock is mud or grain supported. Also if original components were bound together like coral. Also if original components were bound together like coral. Tells about transport history. Tells about transport history.

Folk Classification Carbonate rocks consits of: Carbonate rocks consits of: Allochems—grains Allochems—grains Intersitial material—micrite or spar cement Intersitial material—micrite or spar cement Micrite is "lime mud", the dense, dull-looking sediment made of clay sized crystals of CaCO3. Micrite is "lime mud", the dense, dull-looking sediment made of clay sized crystals of CaCO3. Spar—clear to translucent carbonate cement. Spar—clear to translucent carbonate cement.

Micrite and Spar

Folk Continued Name is built up by stringing together all the allochem names in order from least to most abundant, and then adding the interstitial material name ("matrix" below for short). For example, a rock like this: Oolites + Fossils + Spar matrix = Oo bio sparite The name is written as one word, Oobiosparite. Another example (again allochems from least to most abundant): Pellets + Oolites + Fossils + Micrite matrix = pel oo bio micrite The name is written as one word, Peloobiomicrite. But what if there is both micrite and spar matrix? The system is the same; just list them from least to most abundant. Fossils + Spar matrix + Micrite matrix = bio spar micrite Name is built up by stringing together all the allochem names in order from least to most abundant, and then adding the interstitial material name ("matrix" below for short). For example, a rock like this: Oolites + Fossils + Spar matrix = Oo bio sparite The name is written as one word, Oobiosparite. Another example (again allochems from least to most abundant): Pellets + Oolites + Fossils + Micrite matrix = pel oo bio micrite The name is written as one word, Peloobiomicrite. But what if there is both micrite and spar matrix? The system is the same; just list them from least to most abundant. Fossils + Spar matrix + Micrite matrix = bio spar micrite

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

pisolites--Pisolites are ooids greater than 2mm in size pisolites--Pisolites are ooids greater than 2mm in size Similar environments as ooids Similar environments as ooids

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

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

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

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

dolostone--A dolostone is a rock compose of % dolomite. dolostone--A dolostone is a rock compose of % dolomite.