carbonate factory
TRANSCRIPT
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.
2. Biological Factor
� 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
2. Biological Factor
3. Climatic Zone
4. Temperature-Salinity4. Temperature-Salinity
5. Clastic Sediment Input
6. Water Depth-Turbidity
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
2. Biological Factor
3. Climatic Zone
4. Temperature-Salinity4. Temperature-Salinity
5. Clastic Sediment Input
6. Water Depth-Turbidity
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
2. Biological Factor
3. Climatic Zone
4. Temperature-Salinity4. Temperature-Salinity
5. Clastic Sediment Input
6. Water Depth-Turbidity
5. Clastic Sediment Input
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
2. Biological Factor
3. Climatic Zone
4. Temperature-Salinity4. Temperature-Salinity
5. Clastic Sediment Input
6. Water Depth-Turbidity
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.