lec#6 carbonate

mudtstone

less than 10% grain

What is spar? Micrite?

Spar (or Sparry Calcite) is translucent calcite cement that fills pores between grains. Micrite is lime mud matrix.

Grains

(skeletal, intraclasts, ooids, pellets) form the framework

Pores

between grains can remain as pores, be filled by matrix (mud), or be filled by cement (spar = translucent calcite cement

How are terrigenous and carbonate sediments the same and different?

They are the same in that both have a framework of grains and use mud to indicate slow currents. They are different because carbonates commonly undergo surface cementation and significant dissolution/change during diagenesis.

Carbonates

"largely analogous" to terrigenous (clastic) sediments because both are made of grains.

Framework

made of grains like skeletal fragments, intraclasts, ooids, and pellets.

Pores

filled by either matrix (mud) or cement

Higher water velocities

remove mud, leaving pores to be filled by spar later.

There are two main Classification of Carbonate Rock

• Folk (1959) and Dunham (1962).

• Folk is primarily descriptive; Dunham is both descriptive and interpretive.

Bob Folk

focuses on what the rock looks like in thin section under a microscope.

Be able to use the Folk classification. Know the rock types.

[Intrasparite, Intramicrite, Oosparite, Oomicrite, Biosparite, Biomicrite, Pelsparite, and Pelmicrite]

wackestone

more than 10% grain( mostly mud)

packstone

Grain-supported, but still contains mud.

grainstone

Grain-supported, lacks mud.

Mudstone

Mud-supported, <10% grains.

boundstone

original comps bound together at time of deposition

Dunham assumed that the % mud in a deposit reflected what?

He interpreted the amount of mud to reflect the [environmental conditions]specifically the energy or velocity of the water) at the time of deposition.

floatstone

matrix supported/ allochtonous/ less than 10% grains and smaller than 2mm

Folk: Micrite

Dunham: Mudstone

Folk: Oosparite

Dunham: Grainstone

Folk: Biomicrite

Dunham: Packstone

Folk: Biosparite

Dunham: Grainstone

Folk: Pelsprite

Dunham: Grainstone

Folk: Intrasparite

Dunham: Grainstone

(Embry & Klovan) 1971

• Sub-divides Boundstone into Bafflestones, Bindstones, and Framestones.

What terms are applied to different types of boundstones?

[Bafflestones, Bindstones, and Framestones, rudstone anf floatstone

[Bafflestones, Bindstones, and Framestones

Both have >10% grains larger than 2mm. A [Floatstone](Slide 12) is matrix-supported (grains "float" in mud), while a [Rudstone](Slide 12) is grain-supported.

rudstone

supported by > 2mm comps/ allochtonous/ less than 10% grains and smaller than 2mm

framestone

would not make a good reservoir, by organisms that build a rigid framework/ authochthonous

bindstone

by organisms that encrust and bind/ autochthonous

bafflestone

fromed by organisms that act as baffle or slow down water or trap sediment/ autochthonous

allochthonous

original components not bound organically at deposition

autochthonous

original components bound organically at deposition

embry and Klovan (1971)

further sub-divided Dunham categories into divided boundstone and allochems

bindstone

Formed by organisms (like Cyanobacteria) that grow in layers and "bind" or glue the sediment together.

What is a stromatolite?

are layered mounds or columns formed by layers of cyanobacteria that trap and bind sediment in shallow water.

Bob Folk

emphasized what carbonate looks like in thin section and what sorts of particles are seen under the microscope

framestone

coral reef

Which rocks have more organic matter: black shale or oil shale?

oil shale contains a higher concentration of organic matter (specifically kerogen) compared to typical black shale.

Carbonaceous Sediments (Rocks) Classification

grainstone

The three main categories are

Shale, Coal, and Petroleum

coal

is an organic sedimentary rock formed from the accumulation and preservation of plant materials.

Coal Formation

The process requires Burial, Temperature (Heat), Pressure, and Time.

What is the main component of coal? How is coal formed?

The main component is Carbon. It is formed when plant debris is buried and subjected to heat and pressure over geological time.

What time was prolific for coal formation?

The [Carboniferous]

What are the main types of coal and their characteristics? What is coal classification based on?

The types are [Peat, Lignite, Bituminous, and Anthracite] Classification is based on [Carbon % and energy content]

peat

Low carbon (<60%); partially carbonized plant debris.

Lignite

Lowest rank of "true" coal; brown-black; 60-70% carbon.

Bituminous

Most abundant rank in the US; 70-87% carbon; high heating value.

Anthracite

Highest rank; shiny/hard; >87% carbon.

Which countries have large coal reserves and burn it the most?

Reserves are highest in the [US, Russia, and germany, brazil, south africa]

coal resources

north america(27%), europe(28%), asia(18%)