Grains and Skeletal Parts

As a closing remark, if we accept the carbon isotopic record of carbonates and organic carbon through geologic time as an index of the relative accumulation rates of inorganic and organic carbon on the sea floor, the carbonate carbon accumulation rate has been remarkably constant (Chapter 10). This near constancy has been maintained despite changes in Earth s surface physical and chemical environment and biotic evolution. 

In a further section, we emphasize the mineralogy and chemistry of carbonate skeletal grains, because of their abundance in Phanerozoic sediments, and their potential usefulness in paleoenvironmental interpretation. To provide the reader at this point with some idea of the complexity of skeletal carbonate grains, Tables 5.2 and 5.3 summarize the chemistry, mineralogy and structure of major 

Type of Organism Most Common Mineralogy Range in Chemical Composition CaCC 3 MgC03 S1CO3 (mole %) (mole %) (mean mole %)  

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