carbonate factory

The Carbonate FactoryThe Carbonate Factory

� The carbonate factory is defined as the shallow illuminted

seafloor, where sediment particles are ‘born’ through

crystalization of skeletons or precipitation out of sea

water. Many consider the carbonate factory to be the core

of carbonate deposition throughout the world.of carbonate deposition throughout the world.

� The carbonate factory is governed by the Goldilocks

theory, where the environmental conditions have to be

just right. The water can’t be to warm nor to cold to deep

nor to shallow, salinitiy is key along with the amount of

terriginous clastic sediment. Because of this we have picked

six main controlls to talk about.

The Carbonate Factoryhttp://strata.geol.sc.edu/MARINESEDIMENTS/CarbonateShelf/Carbonate_Factory.html

1. Evolution

2. Biological Factor

3. Climatic Zone

4. Temperature-Salinity4. Temperature-Salinity

5. Clastic Sediment Input

6. Water Depth-Turbidity

1. Evolution

� Studies into marine fossils have created benthic

assemblages for the Paleozoic succession that

are based on a specific environmental factor a

key organisms always maintains. For example

distance from the shoreline for brachiopods.distance from the shoreline for brachiopods.

� Different groups of organisms played key roles

in varying times throughout the geologic past as

the earth evolved so too did the organisms

building the carbonate factories.


� The majority of carbonate sediments are produced in

some sort of biologically or biochemically mediated way.

� There are four main types of carbonate sediment

particles:

� Precipitates: formed by direct or biologically medieatedprecipitation of calcium carbonate. Ex. ooids and lime muds

� Bioclasts: the calcareous shells, tests, spicules and other body support structures

� Peloids: agglutinated or cemented carbonate feces or other diagenetically altered carbonate grains

� Lithoclasts: fragments of consolidated, hardened or litifiedsediments

� The majority of carbonate sediments are

produced by the skeletons of and precipitates

surrounding phototrophic organisms.

� Which include most photosynthetic marine � Which include most photosynthetic marine

organisms from microbes and algae to corals

and giant clams.

� However most of these organisms are limited to

near surface environments within the photic

zone.

� The carbonate skeletal deposits can be compared

through time to ancient carbonate deposits because

although the marine species changes with evolution the

arrangement of carbonate particles does not. There are

only two ways in which skeletal carbonates can be only two ways in which skeletal carbonates can be

arranged.

� Whole rigid structures such as corals and snail shells.

� Segmented pieces held together suchas trilobites and clams. Multiple parts held together by some other soft tissue

� Once these carbonate particles are produced and

deposited other biological organisms, such as grasses

and microbes, act as sediment traps and stabilizers.

� In this way the entire carbonate factory is controlled by

and evolves with the biology of its own system.and evolves with the biology of its own system.

1. Waves: on protected factories the waves have little effect upon sediment erosion however when the factory is exposed to the full onslaught of wave energy the delicate parts of the factory are easily ripped off and parts of the factory are easily ripped off and sediment can be drawn away from the shelf.

2. Tides: act on a daily cycle to both bring sediment and nutrients into the factory and draw the factory towards the shore and to remove sediments and water away from the remove sediments and water away from the factory and into deeper water. Tides also change the depth of the water column above the carbonate factory and thus allowing light to go further down into the system.

3. Storms: are a high energy event that typically act to harm the carbonate factory production. Storms can increase the amount of terrigenous sediment brought onto the carbonates as well as do a huge amount of carbonates as well as do a huge amount of damage to the carbonate factory itself. One example are the hurricanes that hit the carribean coral reefs each year. Luckily the larger the energy of the storm typically it’s cyclicity is over longer time scales.

4. Oceanic Currents: often times brings more nutrients and oxygenated waters to the carbonate factories and encourage growth but they also can bring more terrigenous sediments to the area or even suck sediments to the area or even suck carbonate sediments away from the platform.

Another Factor that influences the carbonate factory sediment production is cycles of high sea level vs low sea level. This is very sea level vs low sea level. This is very similar to tidal changes but on a much larger scale.

Times of low sea level expose the carbonate factory to the zone of wave energy circulation and can even place the factory circulation and can even place the factory above the water level. This results in erosion and lithification of the carbonate sediments and can be seen in the sediment record.

1. Evolution


3. Climatic Zone




3. Climatic Zones

There are three main faunal assemblages associated with the carbonate factory.

1. Foramol: includes benthic foraminifera, molluscs,

barnacles, brozoa and calcareous red algae. This

assemblage lives in the cooler waters below 18

degrees Celcius.degrees Celcius.

2. Chlorozoan: composed of hermatipic corals,

calcareous green algae and foramol constituents. This

is the warm water assemblage.

3. Chloralgal: mainly calcareous green algae. These

algae dominate the high salinity assemblages.

Climate influences three environmental conditions for the carbonate factory.

1. Rate of terrigenous clastic sediment input.

2. The amount and rate of evaporation/rainfall.

The evaporation and rainfall play a crucial role in keeping the

water salinity in the exact range needed for optimal growth.

Since most of the carbonate factories form in shallow water

environments the evaporation to rainfall ratio is extremely environments the evaporation to rainfall ratio is extremely

important.

3. The storminess of the sea and it’s cyclicity.

Typically high energy storms can cause damage to delicate

factory organisms and errode sediment away. With a long period

cyclicity the factory can restore itself but if major storm events

happen rapidly it can quickly do more damage than the factories

can overcome.

1. Evolution


3. Climatic Zone




4. Temperature and Salinity Conditions

The oceans are divided into warm warm vs cool water realms at the 18 degree C marker.

� Warm Water systems:

� typically in low latitudes

the photic zone extends to about 70m � the photic zone extends to about 70m

� carbonate production is highest in the upper 10-20m

� produces Chlorozoan assemblages of organisms

� Cool Water systems:

�the photic zones plays little role in

carbonate productioncarbonate production

�lower sedimentation rate than the

warm water factories

�produces Foramol assemblages of sediments

Salinity

� Both organism (fauna and flora) assemblages

succeed in salinities ranging from 32 to 40 ppt.

When the salinity increased above 40 ppt in the

tropics the organism assemblage becomes

Chloralgal.Chloralgal.

� Increasing the salinity above normal ocean

levels reduces the biotic diversity that can

handle an extreme amount of salt.

1. Evolution


3. Climatic Zone





Clastic sediments have a terrigenous

source and arrive at carbonate

platforms through both fluvial and

eolian processes such as river

deposits and wind blown dust.

Also coastal longshore and deep

currents

Ultimatly clastic sediments can shut off carbonate

sediment production and kill the carbonate factory. It

does this in three main ways.

1. Reduction of water transparency

2. Cloggs the feeding and/or respiration of sessile

benthic organisms

3. Increasing nutrient and particulate organic 3. Increasing nutrient and particulate organic

concentration of the water. This causes filamentous

algae to replace the coelenterates in the carbonate

factory. Many organisms in the carbonate platforms

thrive in nutrient poor waters while their competition

cannot. When nutrient levels increase corals and other

organisms lose their advantage and can die off quickly.

1. Evolution


3. Climatic Zone




6. Water Depth and Turbidity

Water Depth and Turbidity are the main controls on the depth of light penetration, which defines the photic zone.

The turbidity is enhanced typically due to clastic The turbidity is enhanced typically due to clastic runoff. Therefore the light penetration is low in the western sides of tropical and subtropical oceans, in areas of upwelling and in areas with high surface productivity above platform areas on eastern sides of the oceans.

The water depths in which the carbonate

factory forms and grows varies greatly

depending upon the morphology and type

of platform developed.

Warm water platforms have shallower Warm water platforms have shallower

water depths while their cool water

counterparts form in much deeeper waters.

Each setting also has a range in which it

grows.

There are some factories that grow

completely in less that 20m of water

and others that extend down to more

than 170m depth.

Typically once a carbonate factory is

successful it extends both up and

down in the water column to find the

ideal light and nutrient concentrations

for the varying organisms living and

creating the factory.

In warm water settings the photic zone

averages 70m deep.

However due to the decreasing light

with depth the majority of carbonate with depth the majority of carbonate

production occurs in the upper 10 to

20 m.

carbonate factory

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