A
carbonate platform is a
sedimentary body which possesses
topographic relief, and is composed of autochthonous calcareous deposits (Wilson, 1975). 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. 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,
water 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 (Carannante et al., 1988). 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 platform, the platform on which the
Great Barrier Reef is growing, and the
Maldive atolls.
[1]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 (
tabulata and
rugosa) were important reef builders.