A carbonate platform is a
sedimentary body which possesses
topographic
Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps.
Topography is a field of geoscience and planetary scie ...
relief, and is composed of
autochthonic calcareous deposits.
Platform growth is mediated by
sessile organisms whose
skeletons build up the
reef or by organisms (usually
microbes) which induce
carbonate precipitation through their
metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run ...
. Therefore, carbonate platforms can not grow up everywhere: they are not present in places where limiting factors to the life of reef-building organisms exist. Such limiting factors are, among others:
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
,
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
temperature,
transparency and pH-Value. For example, carbonate sedimentation along the
Atlantic South American coasts takes place everywhere but at the mouth of the
Amazon River, because of the intense
turbidity of the water there. Spectacular examples of present-day carbonate platforms are the
Bahama Banks under which the platform is roughly 8 km thick, the
Yucatan Peninsula which is up to 2 km thick, the
Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...
platform, the platform on which the
Great Barrier Reef is growing, and the
Maldive atolls. All these carbonate platforms and their associated
reefs are confined to
tropical latitudes. Today's reefs are built mainly by
scleractinian corals, but in the distant past other organisms, like
archaeocyatha (during the
Cambrian) or extinct
cnidaria
Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.
Their distinguishing feature is cnidocytes, specialized cells that ...
(
tabulata and
rugosa) were important reef builders.
Carbonate precipitation from seawater
What makes carbonate platform environments different from other depositional environments is that carbonate is a product of precipitation, rather than being a sediment transported from elsewhere, as for sand or gravel.
This implies for example that carbonate platforms may grow far from the coastlines of continents, as for the Pacific atolls.
The
mineralogic composition of carbonate platforms may be either
calcitic or
aragonitic.
Seawater is oversaturated in carbonate, so under certain conditions CaCO
3 precipitation is possible. Carbonate precipitation is
thermodynamically favoured at high temperature and low
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
. Three types of carbonate precipitation are possible: ''biotically controlled'', ''biotically induced'' and ''abiotic''. Carbonate precipitation is biotically controlled when organisms (such as corals) are present that exploit carbonate dissolved in seawater to build their calcitic or aragonitic skeletons. Thus they may develop hard reef structures. Biotically induced precipitation takes place outside the cell of the organism, thus carbonate is not directly produced by organisms, but precipitates because of their metabolism. Abiotic precipitation, by definition, involves little or no
biological influence.
Classification
The three types of precipitation (abiotic, biotically induced and biotically controlled) cluster into three "carbonate factories". A carbonate factory is the ensemble of the
sedimentary environment, the intervening organisms and the precipitation processes that lead to the formation of a carbonate platform. The differences between three factories is the dominant precipitation pathway and skeletal associations. In contrast, a carbonate platform is a geological structure of parautochotonous carbonate sediments and carbonate rocks, having a morphological relief.
Platforms produced by the "tropical factory"
In these carbonate factories, precipitation is biotically controlled, mostly by
autotrophic organisms. Organisms that build this kind of platforms are today mostly
corals and
green algae, that need sunlight for photosynthesis and thus live in the
euphotic zone (i.e., shallow water environments in which sunlight penetrates easily). Tropical carbonate factories are only present today in warm and sunlit waters of the tropical-subtropical belt, and they have high carbonate production rates but only in a narrow depth window.
The depositional profile of a Tropical factory is called "rimmed" and includes three main parts: a
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into '' coastal lagoons'' (or ''barrier lagoons ...
, a
reef and a slope. In the reef, the framework produced by large-sized skeletons, as those of corals, and by encrusting organisms resists wave action and forms a rigid build up that may develop up to sea-level.
The presence of a rim produces restricted circulation in the back reef area and a lagoon may develop in which carbonate mud is often produced. When reef accretion reaches the point that the foot of the reef is below wave base, a slope develops: the sediments of the slope derive from the erosion of the margin by waves, storms and gravitational collapses.
This process accumulates coral debris in clinoforms. The maximum angle that a slope can achieve is the settlement angle of gravel (30–34°).
Platforms produced by the "cool-water factory"
In these carbonate factories, precipitation is biotically controlled by
heterotrophic organisms, sometimes in association with photo-autotrophic organisms such as
red algae. The typical skeletal association includes
foraminifers, red algae and
molluscs. Despite being autotrophic, red algae are mostly associated to heterotrophic carbonate producers, and need less light than green algae. The range of occurrence of cool-water factories extends from the limit of the tropical factory (at about 30◦) up to polar latitudes, but they could also occur at low latitudes in the thermocline below the warm surface waters or in upwelling areas.
This type of factories has a low potential of carbonate production, is largely independent from sunlight availability, and can sustain a higher amount of nutrients than tropical factories. Carbonate platforms built by the "cool-water factory" show two types of geometry or depositional profile, i.e., the homoclinal ramp or the distally-steepened ramp. In both geometries there are three parts: the inner ramp above the fair weather
wave base
The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. At water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion ab ...
, the middle ramp, above the storm wave base, the outer ramp, below the storm wave base. In distally steepened ramps, a distal step is formed between the middle and outer ramp, by the in situ accumulation of gravel-sized carbonate grains
Platforms produced by the "mud-mound factory"
These factories are characterised by abiotic precipitation and biotically induced precipitation. The typical environmental settings where "mud-mound factories" are found in the Phanerozoic are dysphotic or
aphotic
The aphotic zone (aphotic from Greek prefix + "without light") is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1 percent of sunlight penetrates. Above the apho ...
, nutrient-rich waters that are low in oxygen but not
anoxic
The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts:
* Anoxic waters, sea water, fresh water or groundwater that are depleted of diss ...
. These conditions often prevail in the thermocline, for example at intermediate water depths below the ocean's
mixed layer.
The most important component of these platforms is fine-grained carbonate that precipitates in situ (
automicrite) by a complex interplay of biotic and abiotic reactions with microbes and decaying organic tissue.
Mud-mound factories do not produce a skeletal association, but they have specific
facies and microfacies, for example
stromatolites, that are laminated
microbialites, and
thrombolites, that are
microbialites characterized by clotted peloidal fabric at the microscopic scale and by dendroid fabric at the hand-sample scale.
The geometry of these platforms is mound-shaped, where all the mound is productive, including the slopes.
Geometry of carbonate platforms
Several factors influence the geometry of a carbonate platform, including inherited topography, synsedimentary
tectonics, exposure to currents and
trade winds. Two main types of carbonate platforms are distinguished on the base of their geographic setting: isolated (as
Maldives atolls) or epicontinental (as the
Belize
Belize (; bzj, Bileez) is a Caribbean and Central American country on the northeastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a wa ...
reefs or the
Florida Keys). However, the one most important factor influencing geometries is perhaps the type of carbonate factory. Depending on the dominant carbonate factory, we can distinguish three types of carbonate platforms: T-type carbonate platforms (produced by "tropical factories"), C-type carbonate platforms (produced by "cool-water factories"), M-type carbonate platforms ("produced by mud-mound factories"). Each of them has its own typical geometry.
T-type carbonate platforms
The depositional profile of T-type carbonate platforms can be subdivided into several
sedimentary environments.
The carbonate hinterland is the most landward environment, composed by weathered
carbonate rocks. The evaporitic
tidal flat is a typical low-energy environment.
The internal
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into '' coastal lagoons'' (or ''barrier lagoons ...
, as the name suggests, is the part of platform behind the reef. It is characterised by shallow and calm waters, and so it is a low-energy sedimentary environment. Sediments are composed by reef fragments, hard parts of organisms and, if the platform is epicontinental, also by a terrigenous contribution. In some lagoons (e.g., the
Florida Bay),
green alga
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
e produce great volumes of carbonate mud. Rocks here are
mudstones to
grainstones, depending on the energy of the environment.
The
reef is the rigid structure of carbonate platforms and is located between the internal lagoon and the slope, in the platform margin, in which the framework produced by large-sized skeletons, as those of corals, and by encrusting organisms will resist wave action and form a rigid build up that may develop up to sea-level. Survival of the platform depends on the existence of the reef, because only this part of the platform can build a rigid, wave-resistant structure. The reef is created by essentially in-place,
sessile organisms. Today's reefs are mostly built by
hermatypic corals. Geologically speaking, reef rocks can be classified as massive
boundstones.
The
slope
In mathematics, the slope or gradient of a line is a number that describes both the ''direction'' and the ''steepness'' of the line. Slope is often denoted by the letter ''m''; there is no clear answer to the question why the letter ''m'' is use ...
is the outer part of the platform, connecting the reef with the basin. This depositional environment acts as sink for excess carbonate sediment: most of the sediment produced in the lagoon and reef is transported by various processes and accumulates in the slope, with an inclination depending on the grain size of sediments, and that could attain the settlement angle of gravel (30-34°) at most.
The slope contains coarser sediments than the reef and lagoon. These rocks are generally
rudstones or
grainstones.
The periplatform basin is the outermost part of the t-type carbonate platform, and carbonate sedimentation is there dominated by density-cascating processes.
The presence of a rim damps the action of waves in the back reef area and a lagoon may develop in which carbonate mud is often produced. When reef accretion reaches the point that the foot of the reef is below wave base, a slope develops: the sediments of the slope derive from the erosion of the margin by waves, storms and gravitational collapses. This process accumulates coral debris in clinoforms. Clinoforms are
beds that have a sigmoidal or tabular shape, but are always deposited with a primary inclination.
The size of a T-type carbonate platform, from the hinterland to the foot of the slope, can be of tens of kilometers.
C-type carbonate platforms
C-type carbonate platforms are characterized by the absence of early
cementation and
lithification, and so the sediment distribution is only driven by
waves
Waves most often refers to:
* Waves, oscillations accompanied by a transfer of energy that travel through space or mass.
* Wind waves, surface waves that occur on the free surface of bodies of water.
Waves may also refer to:
Music
*Waves (ban ...
and, in particular, it occurs above the
wave base
The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. At water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion ab ...
. They show two types of geometry or depositional profile, i.e., the homoclinal ramp or the distally-steepened ramp. In both geometries there are three parts. In the inner ramp, above the fair weather
wave base
The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. At water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion ab ...
, the carbonate production is slow enough that all sediments may be transported offshore by waves, currents and storms. As a consequence, the shoreline may be retreating, and so in the inner ramp there may be a cliff caused by erosional processes. In the middle ramp, between the fair weather wave base and the storm wave base, carbonate sediment remains in place and can be reworking only by the storm waves. In the outer ramp, below the storm wave base, fine sediments may accumulate. In distally steepened ramps, a distal step is formed between the middle and outer ramp, by the in situ accumulation of gravel-sized carbonate grains (e.g.,
rhodoliths) only episodically moved by currents. Carbonate production occurs along the full depositional profile in this type of carbonate platforms, with an extra production in the outer part of the middle ramp, but carbonate production rates are always less than in the T-type carbonate platforms.
M-type carbonate platforms
M-type carbonate platforms are characterized by an inner platform, an outer platform, an upper slope made by microbial
boundstone, and a lower slope often made by
breccia
Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...
. The slope may be steeper than the angle of repose of gravels, with an inclination that may attain 50°.
In the M-type carbonate platforms the carbonate production mostly occurs on the upper slope and in the outer part of the inner platform.
Carbonate platforms in the geological record
Sedimentary sequences show carbonate platforms as old as the
Precambrian, when they were formed by
stromatolitic sequences. In the
Cambrian carbonate platforms were built by
archaeocyatha. During
Paleozoic brachiopod (richtofenida) and
stromatoporoidea reefs were erected. At the middle of the Paleozoic era corals became important platforms builders, first with
tabulata (from the
Silurian) and then with
rugosa (from the
Devonian).
Scleractinia become important reef builders beginning only in the
Carnian (upper
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...
). Some of the best examples of carbonate platforms are in the
Dolomites
The Dolomites ( it, Dolomiti ; Ladin: ''Dolomites''; german: Dolomiten ; vec, Dołomiti : fur, Dolomitis), also known as the Dolomite Mountains, Dolomite Alps or Dolomitic Alps, are a mountain range located in northeastern Italy. They form pa ...
, deposited during the Triassic. This region of the Southern
Alps contains many well preserved isolated carbonate platforms, including the
Sella,
Gardenaccia,
Sassolungo and
Latemar. The middle
Liassic "bahamian type" carbonate platform of Morocco (Septfontaine, 1985) is characterised by the accumulation of autocyclic regressive
cycles, spectacular supratidal deposits and
vadose diagenetic features with
dinosaur tracks. The Tunisian coastal "chotts" and their cyclic muddy deposits represent a good recent equivalent (Davaud & Septfontaine, 1995). Such cycles were also observed on the
Mesozoic Arabic platform, Oman and Abu Dhabi (Septfontaine & De Matos, 1998) with the same microfauna of foraminifera in an almost identical biostratigraphic succession.
In the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
period there were platforms built by
bivalvia (
rudists
Rudists are a group of extinct box-, tube- or ring-shaped marine heterodont bivalves belonging to the order Hippuritida that arose during the Late Jurassic and became so diverse during the Cretaceous that they were major reef-building organis ...
).
Sequence stratigraphy of carbonate platforms
With respect to the
sequence stratigraphy of siliciclastic systems, carbonate platforms present some peculiarities, which are related to the fact that carbonate sediment is precipitated directly on the platform, mostly with the intervention of living organisms, instead of being only transported and deposited.
Among these peculiarities, carbonate platforms may be subject to drowning, and may be the source of sediment via highstand shedding or slope shedding.
Drowning
Drowning of a carbonate platform is an event where the
relative sea level rise is faster than the accumulation rate on a carbonate platform, which eventually leads to the platform to submerge below the
euphotic zone.
In the
geologic record of a drowned carbonate platform,
neritic deposits change rapidly into deep-marine sediments. Typically
hardgrounds with
ferromanganese oxides,
phosphate or
glauconite crusts lie in between of
neritic and deep-marine sediments.
Several drowned carbonate platforms have been found in the geologic record. However, it has not been very clear how the drowning of carbonate platforms exactly happen. Modern carbonate platforms and reefs are estimated to grow approximately 1,000 μm/yr, possibly several times faster in the past. 1,000 μm/yr growth rate of carbonates exceeds by orders of
magnitude any
relative sea level rise that is caused by long-term subsidence, or changes in
eustatic sea level. Based on the rates of these processes, drowning of the carbonate platforms should not be possible, which causes "the paradox of drowned carbonate platforms and reefs".
Since drowning of carbonate platforms requires exceptional rise in the
relative sea level, only limited number of processes can cause it. According to Schlager,
only anomalously quick rise of
relative sea level or
benthic growth reduction caused by deteriorating changes in the environment could explain the drowning of platforms. For instance, regional downfaulting, submarine
volcanism or
glacioeustacy could be the reason for rapid rise in
relative sea level, whereas for example changes in oceanic
salinity might cause the environment to become deteriorative for the carbonate producers.
One example of a drowned carbonate platform is located in
Huon Gulf,
Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
. It is believed to be drowned by rapid sea level rise caused by
deglaciation and subsidence of the platform, which enabled coralline algal-
foraminiferal nodules and
halimeda limestones to cover the
coral reefs.
Plate movements carrying carbonate platforms to
latitudes unfavourable for carbonate production are also suggested to be one of the possible reasons for drowning.
For example,
guyots located in the Pacific Basin between
Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
an and
Mariana Islands are believed to be transported to low southern
latitudes (0-10°S) where equatorial
upwelling occurred.
High amounts of
nutrients and higher productivity caused decrease in water transparency and increase in bio-eroders populations, which reduced carbonate accumulation and eventually led to drowning.
Highstand shedding
Highstand shedding is a process in which a carbonate platform produces and sheds most of the sediments into the adjacent basin during highstands of sea level. This process has been observed on all rimmed carbonate platforms in the Quaternary, such as the
Great Bahama Bank. Flat topped, rimmed platforms with steep slopes show more pronounced highstand shedding than platforms with gentle slopes and cool water carbonate systems.
Highstand shedding is pronounced on
tropical carbonate platforms because of the combined effect of sediment production and
diagenesis.
Sediment production of a platform increases with its size, and during
highstand the top of the platform is flooded and the productive area is bigger compared to the
lowstand conditions, when only a minimal part of the platform is available for production.
The effect of increased highstand production is enhanced by the rapid
lithification of carbonate during lowstands, because the exposed platform top is
karstified rather than eroded, and does not export sediment.
Slope shedding
Slope shedding is a process typical of
microbial platforms, in which the carbonate production is nearly independent from sea level oscillations. The carbonate factory, composed of microbial communities precipitating
microbialites, is insensitive to light and can extend from the platform break down the slope to hundreds of meters in depth. Sea level drops of any reasonable amplitude would not significantly affect the slope production areas. Microbial boundstone slope systems are remarkably different from tropical platforms in sediment productions profiles, slope readjustment processes and sediment sourcing. Their
progradation
In sedimentary geology and geomorphology, the term progradation refers to the growth of a river delta farther out into the sea over time. This occurs when the volume of incoming sediment is greater than the volume of the delta that is lost through ...
is independent from platform sediment shedding and largely driven by slope shedding.
Examples of margins that may be affected of slope shedding that are characterized by various contributions of microbial carbonate growth to the upper slope and margin, are:
* the
Canning Basin
The Canning Basin is a geological basin located in Western Australia. Deposition of sediments began after early-Ordovician thermal subsidnce, and continued into the Early Cretaceous.
The Basin covers approximately 506,000 km2 of which appr ...
in Australia
* the Guilin platform in the southern China
* the Permian of the
US Permian Basin
* the middle Triassic carbonate platforms of the
Dolomites
The Dolomites ( it, Dolomiti ; Ladin: ''Dolomites''; german: Dolomiten ; vec, Dołomiti : fur, Dolomitis), also known as the Dolomite Mountains, Dolomite Alps or Dolomitic Alps, are a mountain range located in northeastern Italy. They form pa ...
.
Gallery
File:Cycle émersif Maroc.jpg, "Shallowing upward" cycle in the middle Lias of the high Atlas (Morocco). Algal dolomitized laminations on top.
File:Cycle émersif Oman.jpg, "Shallowing upward" cycles in the lagoonal Lias of the Musandam Peninsula. (N-Oman).
File:Cycle émersif Musandam.jpg, "Shallowing upward" liassic cycles arranged in decametric sequences, Musandam Peninsula, (N-Oman).
File:Cycle émersif Laghdar.jpg, "Shallowing upward" cycle in the Middle Jurassic (Saghtan form.) of the jbel Laghdar Range (Oman).
File:Desiccation Rnim.jpg, Desiccation figures on top of a regressive sequence; Middle liassic, High Atlas, Morocco.
File:Calcretes et ammonites.jpg, Ammonites and belemnites washed over a supratidal surface (calcretes and " teepees"); Middle Liassic of the High Atlas, Morocco.
File:Brèche de tempête.jpg, Hurricane breccia cemented (early diagenesis) at the surface of a bed, top of a regressive, metric, sequence. Middle Lias, High Atlas.
File:Pisolithes vadoses.jpg, Vadose ferrugenous pisolites (soil) and coastal (tempestite) sediment with birdseyes in an outer platform environment. Aerial diagenesis. Middle liassic, High Atlas, Morocco.
File:Keystone vugs meniscus.jpg, Meniscus and point contact cement in a marine grainstone with displaced foraminifera (by tide and hurricanes) on the supratidal flat of the middle liassic platform of Morocco. Top of emersive cycle. Middle Atlas.
File:Calcretes remaniés dolomie.jpg, Reworked calcretes concretions from the supratidal environment in a marine (dolomitised) sediment displaced by hurricanes on the inner platform flat. Top of emersive sequence. High Atlas, Morocco.
File:Ciment stalactite vadose.jpg, Stalactitic cement in sediment from the supratidal zone, vadose environment, top of "shallowing upward" sequence. Middle Liassic, High Atlas. Thin section. L = 0.3 mm.
File:Traces dino géant.jpg, Giant dinosaur tracks (sauropod) on top of a regressive sequence, Middle Liassic, High Atlas, Morocco.
File:Calcretes et birdseyes.jpg, Vadose stalactitic cement filling an horizontal cavity in a marine coastal sediment, outer platform. Birdseyes in the allodapic (tidal or tempestite) grainstone point to an aerial diagenesis. High Atlas, Morocco.
File:Séquences Lias Todhra.jpg, Autocyclic filling (metric to hectometric) sequences in the Middle Liassic lagoon, South (Todhra) of the High Atlas, Morocco.
File:Teepee supratidal flat.jpg, "Teepee" structure, due to increasing sediment volume by dolomitisation on the inner platform supratidal flat. Top of emersive cycle. Middle Lias, High Atlas.
File:Carottes chott tunisien.jpg, Quaternary to recent equivalent of a "shallowing upward sequence", cores in a Tunisian "chott", intertidal laminations in yellow.
File:Tunisie teepee.jpg, Recent "teepee" structures in a Tunisian salt lagoon, "chott".
File:Tunisie carottes Zarzis.jpg, Recent equivalents of "shallowing upward sequences", cores in a Tunisian salt lagoon, "chott".
File:Tunisie gypse.jpg, Top of a regressive sequence with algal laminations (yellow) and crystallised gypsum, salt lagoon "chott", Tunisia.
File:Tunisie tempête.jpg, Eolian bioclastic (calcareous algae and porcellaneous foraminifera) sand dune on Tunisian shore.
See also
*
Ocean bank (topography)
An ocean bank, sometimes referred to as a fishing bank or simply bank, is a part of the seabed that is shallow compared to its surrounding area, such as a shoal or the top of an underwater hill. Somewhat like continental slopes, ocean bank sl ...
*
Bahama Banks
Footnotes
References
* Davaud E. & Septfontaine M. (1995): "Post-mortem onshore transportation of epiphityc foraminifera: recent example from the Tunisian coast line". ''Jour. Sediment. Research'', 65/1A, 136–142.
* Bosellini A., 1984, "Progradation geometries of carbonate platforms: examples from the Triassic of the Dolomites, northern Italy". ''Sedimentology'', Vol. 31, pp. 1–24
"Bahamas Introduction" (Accessed 3/8/06)* Pinet P. R., 1996, ''Invitation to Oceanography''. St. Paul: West Publishing Company,
* Septfontaine M. 1985, "Depositional environments and associated foraminifera (lituolids) in the middle liassic carbonate platform of Morocco." ''Rev. de Micropal.'' 28/4 265–289. See also www.palgeo.ch/publications.
{{Physical oceanography, state=collapsed
Carbonates
Sedimentology
Marine geology
.
Submarine topography
Sedimentary rocks