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 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 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.Typicaly 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 production occurs in the upper 10 to 20 m.
Index to carbonate shelf sediments