Calcium carbonate oxygen isotopic ratio determination

Calcium carbonate is also the main constituent of the shells of sea animals, which make their shells from elements acquired from the surrounding waters. Now, the degree of fractionation of the oxygen isotopes as well as the formation of mineral carbonates and of animal shells in sea waters are determined on the basis of the temperature-dependent fractionation of the isotopes of oxygen the oxygen isotope composition of these materials reflects, therefore, the temperature at the time of their formation. Thus determining the isotope ratio between the stable isotopes of oxygen... 

In addition to information about diet and seasonality, shells at archaeological sites provide information about the local habitat and climate change. Different species of shellfish live in different depths of water, and prefer different temperatures, salinity, and amounts of current. Shells are composed of calcium carbonate (CaCO ) which is a molecule composed of calcium, carbon, and oxygen. The exact ratio of oxygen isotopes in shell depends on the temperature of the water in which the shell formed. Determination of that ratio in the shell can provide information on changes in water temperature (correlated with air temperature) over time. That information can be used to estimate where along a coast the shell is coming from. 

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