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GEOL 325: Stratigraphy & Sedimentary Basins University of South Carolina Spring 2005. An Overview of Carbonates. Professor Chris Kendall EWS 304 kendall@sc.edu 777.2410. Precipitated Sediments & Sedimentary Rocks. An Epitaph to Limestones & Dolomites. Lecture Series Overview.

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GEOL 325: Stratigraphy & Sedimentary BasinsUniversity of South CarolinaSpring 2005

An Overview of Carbonates

Professor Chris Kendall

EWS 304

kendall@sc.edu

777.2410

GEOL 325 Lecture 4: Carbonates

precipitated sediments sedimentary rocks

Precipitated Sediments & Sedimentary Rocks

An Epitaph to

Limestones & Dolomites

lecture series overview
Lecture Series Overview
  • sediment production
  • types of sediment and sedimentary rocks
  • sediment transport and deposition
  • depositional systems
  • stratigraphic architecture and basins
  • chrono-, bio-, chemo-, and sequence stratigraphy
  • Earth history

GEOL 325 Lecture 4: Carbonates

slide4

Sedimentary rocks are the product of the creation, transport, deposition, and diagenesis of detritus and solutes derived from pre-existing rocks.

slide5

Sedimentary rocks are the product of the creation, transport, deposition, and diagenesis of detritus and solutes derived from pre-existing rocks.

sedimentary rocks
Sedimentary Rocks
  • Detrital/Siliciclastic Sedimentary Rocks
    • conglomerates & breccias
    • sandstones
    • mudstones
  • Carbonate Sedimentary Rocks
    • carbonates
  • Other Sedimentary Rocks
    • evaporites
    • phosphates
    • organic-rich sedimentary rocks
    • cherts
    • volcaniclastic rocks

GEOL 325 Lecture 4: Carbonates

lecture outline
Lecture Outline
  • How photosynthesis, warm temperatures & low pressures in shallow water control carbonate distribution
  • How carbonate sediment types is tied to depositional setting
  • How most mud lime mud has a bio-physico-chemical origin
  • Origins of bio-physico-chemical grains:- ooids, intraclasts, pellets, pisoids
  • Separation of bioclastic grains:- foram’s, brach’s, bryozoan, echinoids, red calc’ algae, corals, green calc’ algae, and molluscs by mineralogy & fabric
  • How CCD controls deepwater carbonate ooze distribution
  • How Folk & Dunham’s classifications are used for carbonate sediments
  • How most diagenesis, dolomitization, & cementation of carbonates takes place in near surface & trace elements are used in this determination
  • How Stylolites develop through burial & solution/compaction

GEOL 325 Lecture 4: Carbonates

limestones form where
Limestones Form - Where?
  • Shallow Marine –Late Proterozoic to Modern
  • Deep Marine – Rare in Ancient & commoner in Modern
  • Cave Travertine and Spring Tufa – both Ancient & Modern
  • Lakes – Ancient to Modern

GEOL 325 Lecture 4: Carbonates

co 2 temperature pressure effect
CO2 - Temperature & Pressure Effect!
  • High temperatures, low pressure & breaking waves favor carbonate precipitation
  • CO2 + 3H2O = HCO3-1 + H3O+1 + H2O = CO3-2 + 2H3O+1
  • Carbon dioxide solubility decreases in shallow water and with rising in temperature
  • At lower pressure CO2 is released & at higher pressure dissolves
  • HCO3-1 and CO3-2 are less stable at lower pressure but more stable at higher pressure
  • HCO3-1 and CO3-2 have lower concentration in warm waters but higher concentrations in colder waters

GEOL 325 Lecture 4: Carbonates

calcium carbonate solubilty
Calcium Carbonate - Solubilty
  • Note calcium carbonate dissociation: CaCO3= Ca+2 + CO3-2
  • CaCO3 is less soluble in warm waters than cool waters
  • CaCO3 precipitates in warm shallow waters but is increasingly soluble at depth in colder waters
  • CO2 in solution buffers concentration of carbonate ion (CO3-2)
  • Increasing pressure elevates concentrations of HCO3-1 & CO3-2 (products of solubility reaction) in sea water
  • CaCO3 more soluble at higher pressures & with decreasing temperature

GEOL 325 Lecture 4: Carbonates

controls on carbonate accumulation
Controls on Carbonate Accumulation
  • Temperature (climate) -Tropics & temperate regions favor carbonate production: true of ancient too!
  • Light – Photosynthesis drives carbonate production
  • Pressure – “CCD” dissolution increases with depth
  • Agitation of waves - Oxygen source & remove CO2
  • Organic activity - CaCO3 factories nutrient deserts
  • Sea Level – Yield high at SL that constantly changes
  • Sediment masking - Fallacious!

GEOL 325 Lecture 4: Carbonates

limestones chemical or bochemical
Limestones – Chemical or Bochemical

Distinction between biochemical & physico-chemical blurred by ubiquitous cyanobacteria of biosphere!

  • Shallow sea water is commonly saturated with respect to calcium carbonate
  • Dissolved ions expected to be precipitated as sea water warms, loses CO2 & evaporates
  • Organisms generate shells & skeletons from dissolved ions
  • Metabolism of organisms cause carbonate precipitation

GEOL 325 Lecture 4: Carbonates

biological carbon pump
Biological Carbon Pump
  • Carbon from CO2 incorporated in organisms through photosynthesis, heterotrophy & secretion of shells
  • > 99% of atmospheric CO2 from volcanism removed by biological pump is deposited as calcium carbonate & organic matter
  • 5.3 gigatons of CO2 added to atmosphere a year but only 2.1 gigatons/year remains; the rest is believed sequestered as aragonite & calcite

GEOL 325 Lecture 4: Carbonates

carbonate mineralogy
Carbonate Mineralogy
  • Aragonite – high temperature mineral
  • Calcite – stable in sea water & near surface crust
    • Low Magnesium Calcite
    • High Magnesium Calcite
      • Imperforate foraminifera
      • Echinoidea
  • Dolomite – stable in sea water & near surface
  • Carbonate mineralogy of oceans changes with time!

GEOL 325 Lecture 4: Carbonates

slide20

TROPICS

TEMPERATE OCEANS

GEOL 325 Lecture 4: Carbonates

slide22

Basin

Ramp

Open

Shelf

Restricted

Shelf

GEOL 325 Lecture 4: Carbonates

slide23

Basin

Open

Shelf

Rim

Restricted

Shelf

GEOL 325 Lecture 4: Carbonates

carbonate components the key
Carbonate Components – The Key
  • Interpretation of depositional setting of carbonates is based on
    • Grain types
    • Grain packing or fabric
    • Sedimentary structures
    • Early diagenetic changes
  • Identification of grain types commonly used in subsurface studies of depositional setting because, unlike particles in siliciclastic rocks, carbonate grains generally formed within basin of deposition
  • NB: This rule of thumb doesn’t always apply

GEOL 325 Lecture 4: Carbonates

carbonate particles
Carbonate Particles
  • Subdivided into micrite (lime mud) & sand-sized grains
  • These grains are separated on basis of shape & internal structure
  • They are subdivided into: skeletal & non-skeletal (bio-physico-chemical grains)

GEOL 325 Lecture 4: Carbonates

lime mud or micrite
Lime Mud or Micrite

GEOL 325 Lecture 4: Carbonates

slide27

Lime Mud or Micrite

GEOL 325 Lecture 4: Carbonates

slide28

LIME MUD

ACCUMULATES

ON BANK, OFF BANK

& TIDAL FLATS

WHITING

GEOL 325 Lecture 4: Carbonates

slide29

Three Creeks Tidal Flats

GEOL 325 Lecture 4: Carbonates

slide30

Lime Mud

-

Ordovician

Kentucky

GEOL 325 Lecture 4: Carbonates

carbonate bio physico chemical grains
Carbonate Bio-physico-chemical Grains
  • Ooids
  • Grapestones and other intraclasts
  • Pellets
  • Pisolites and Oncolites

GEOL 325 Lecture 4: Carbonates

slide35

Ooids

GEOL 325 Lecture 4: Carbonates

slide37

Aragonitic Ooids

GEOL 325 Lecture 4: Carbonates

slide38

After Scholle, 2003

Aragonitic Ooids

GEOL 325 Lecture 4: Carbonates

slide39

Calcitic &

Aragonitic

Ooids

Great

Salt

Lake

GEOL 325 Lecture 4: Carbonates

slide40

Grapestones

GEOL 325 Lecture 4: Carbonates

slide41

Grapestones

GEOL 325 Lecture 4: Carbonates

slide42

Pellets

GEOL 325 Lecture 4: Carbonates

slide43

Pellets

GEOL 325 Lecture 4: Carbonates

slide48

After Scholle

GEOL 325 Lecture 4: Carbonates

skeletal particles mineralogy
Skeletal Particles - Mineralogy
  • Calcite commonly containing less than 4 mole % magnesium
    • Some foraminifera, brachiopods, bryozoans, trilobites, ostracodes, calcareous nannoplankton, & tintinnids
  • Magnesian calcite, with 4-20 mole % magnesium
    • Echinoderms, most foraminifera, & red algae
  • Aragonite tests
    • Corals, stromatoporoids, most molluscs, green algae, & blue-green algae.
  • Opaline silica
    • sponge spicules & radiolarians

GEOL 325 Lecture 4: Carbonates

slide50

Drafted by Waite 99, after James 1984)

GEOL 325 Lecture 4: Carbonates

slide51

Foraminifera

GEOL 325 Lecture 4: Carbonates

slide52

After Scholle

Foraminifera

GEOL 325 Lecture 4: Carbonates

slide53

Brachiopod

GEOL 325 Lecture 4: Carbonates

slide54

Brachiopods

GEOL 325 Lecture 4: Carbonates

slide55

Brachiopod

GEOL 325 Lecture 4: Carbonates

slide56

Bryozoan

GEOL 325 Lecture 4: Carbonates

slide57

Bryozoan

GEOL 325 Lecture 4: Carbonates

slide58

Trilobite Remains

Ostracod Remains

Calcispheres

GEOL 325 Lecture 4: Carbonates

slide59

Trilobite Carapice

GEOL 325 Lecture 4: Carbonates

slide60

Crinoid

Syntaxial

cement

GEOL 325 Lecture 4: Carbonates

slide61

Red Calcareous Algae

GEOL 325 Lecture 4: Carbonates

surface water organic productivity
Surface Water Organic Productivity
  • Marine algae & cyanobacteria base of marine food chain
  • Fed by available nitrogen and phosphorus
  • Supplied in surface waters by deep water upwelling
  • Vertical upwelling drives high biological productivity at:
    • Equator
    • Western continental margins
    • Southern Ocean around Antarctica
  • Produce biogenous oozes

GEOL 325 Lecture 4: Carbonates

deep water carbonate deposits
Deep Water Carbonate Deposits
  • Deep water pelagic sediments accumulate slowly (0.1-1 cm per thousand years) far from land, and include:
    • abyssal clay from continents cover most of deeper ocean floor
      • carried by winds
      • ocean currents
    • Oozes from organisms' bodies; not present on continental margins where rate of supply of terriginous sediment too high & organically derived material less than 30% of sediment

GEOL 325 Lecture 4: Carbonates

carbonate compensation depth ccd
Carbonate Compensation Depth - CCD
  • Deep-ocean waters undersaturated with calcium carbonate & opalline silica.
  • Biogenic particles dissolve in water column and on sea floor
  • Pronounced for carbonates
  • Calcareous oozes absent below CCD depth
  • CCD varies from ocean to ocean
    • 4,000 m in Atlantic.
    • 500 - 1,500 m in Pacific
  • Siliceous particles dissolve more slowly as sink & not so limited in distribution by depth
  • Nutrient supply controls distribution of siliceous sediments

GEOL 325 Lecture 4: Carbonates

slide67

After James, 1984

GEOL 325 Lecture 4: Carbonates

slide69

After James, 1984

GEOL 325 Lecture 4: Carbonates

carbonate cement fabrics
Carbonate Cement Fabrics
  • Crust or rims coat grains
  • Syntaxial overgrowth – optical continuity with skeletal fabric
    • Echinoid single crystals
    • Brachiopod multiple crystals
  • Blocky equant - final void fill

GEOL 325 Lecture 4: Carbonates

slide81

Isopachus Marine Cement

GEOL 325 Lecture 4: Carbonates

slide83

Meniscus Cement

GEOL 325 Lecture 4: Carbonates

slide96

Evaporation

of mixed

Waters

1. Aragonite

2. Gypsum

3. Anhydrite

4. Dolomite

5. Halite

accumulate

in this order

Influx of

Magnesium

Rich

Continental

Ground

Waters

Influx of

sea water

GEOL 325 Lecture 4: Carbonates

stylolites
Stylolites
  • Dissolution seam(A),
  • Stylolite (B),
  • Highly serrate stylolite (C)
  • Deformed stylolite (D).

Two-dimensional cross-sectonal views of

A few grains are shown schematically to emphasize the change in scale from the previous figure

(after Bruce Railsback)

GEOL 325 Lecture 4: Carbonates

stylolites1
Stylolites

Intergranular contacts as seen in thin section

  • Tangential (A)
  • flattened (B)
  • concavo-convex (C)
  • sutured (D) (after Bruce Railsback)

GEOL 325 Lecture 4: Carbonates

slide109

Stylolites

After Bruce Railsback

GEOL 325 Lecture 4: Carbonates

stylolites2

Stylolites

After Bruce Railsback

lecture conclusions
Lecture Conclusions
  • Photosynthesis, warm temperatures & low pressures in shallow water control carbonate distribution
  • Carbonate sediment types indicate depositional setting
  • Most mud lime mud has a bio-physico-chemical origin
  • Ooid, intraclast, pellet, and pisoid grains have bio-physico-chemical origin
  • Mineralogy & fabric separate foram’s, brach’s, bryozoan, echinoids, red calc’ algae, corals, green calc’ algae, and molluscan skeleletal grains
  • CCD controls deepwater ooze distribution
  • Folk & Dunham are best way to classify carbonates
  • Most diagenesis, dolomitization, & cementation of carbonates takes place in near surface crust & trace elements can be used in this determination
  • Stylolites develop through burial & solution/compaction

GEOL 325 Lecture 4: Carbonates

end of the lecture

End of the Lecture

Lets go for lunch!!!

slide113

Global Climate Cycles

Global climatic cycles, referenced to geologic periods (yellow), megasequences (light purple), sea level cycles (blue), & volcanic output (dark purple).  (Redrawn & modified L. Waite, 2002 after Fischer, 1984)

GEOL 325 Lecture 4: Carbonates

slide114

Phanerozoic Global Climate History

Frakes et al. (1992) have alternating cold & warm states ("cool" & "warm" modes) at comparable time scales to Fischer (1984) cycles but propose older portion of Mesozoic greenhouse (Middle Jurassic to Early Cretaceous) has a cool climate, & presence of seasonal ice at higher latitudes (after L. Waite, 2002)

GEOL 325 Lecture 4: Carbonates

slide115

Copied from Steven Wojtal of Oberlin College

GEOL 325 Lecture 4: Carbonates

co2 temperature pressure effect
CO2 - Temperature & Pressure Effect!
  • Carbonate precipitation favored by high temperatures, low pressure and breaking waves.
  • Solubility of carbon dioxide increases with depth and drops in temperature
  • CO2 + 3H2O = HCO3-1 + H3O+1 + H2O = CO3-2 + 2H3O+1
  • At higher pressure CO2 dissolves & is released at lower pressures
  • HCO3-1 and CO3-2 are more stable at higher pressures but less stable at lower pressures
  • HCO3-1 and CO3-2 reach higher concentrations in colder waters but lower concentration at warm waters

GEOL 325 Lecture 4: Carbonates

slide117

Copied from Steven Wojtal of Oberlin College

GEOL 325 Lecture 4: Carbonates

calcium carbonate solubilty1
Calcium Carbonate - Solubilty
  • Note behavior of calcium carbonate: CaCO3= Ca+2
  • Concentration of carbonate ion (CO3-2) is buffered by amount of CO2 in solution
  • Increasing pressure elevates concentrations of HCO3-1 & CO3-2 (products of solubility reaction) in sea water
  • CaCO3 is more soluble at higher pressures
  • Similar effect occurs with decreasing temperature
  • CaCO3 is more soluble in cool waters than warm waters
  • CaCO3 is increasingly soluble at depth in colder waters but precipitates in warm shallow waters

GEOL 325 Lecture 4: Carbonates

slide119

Copied from Steven Wojtal of Oberlin College

GEOL 325 Lecture 4: Carbonates

slide120

Copied from Suzanne O'ConnellWesleyan College

GEOL 325 Lecture 4: Carbonates

slide121

Copied from Suzanne O'ConnellWesleyan College

GEOL 325 Lecture 4: Carbonates