Isotopic compositions are in widespread use to establish paleoceanographic conditions and geochemical stratigraphy even though there is scant evaluation of phosphate in modern oceans as a reliable indicator of temperature based on oxygen isotopes or Sr ocean chemistry based on 87Sr86Sr ratios. This study will test the usefulness of oxygen isotopic composition and 87Sr/86Sr ratio of shark teeth to provide a direct measure of temperature and related climate of ancient biogenic phosphate. Principal Investigators will evaluate isotope equilibria between shark tooth apatite and ocean water. Modern species of sharks from well-known habitats will be used to determine the relationship of isotopic composition and ocean water and determine the effect of habitat on the isotope composition of apatite in modern sharks. Accompanying determinations of the distribution of strontium, oxygen, and carbon isotopes in shark teeth and measurements of the isotopic composition of separated dentine and enameloid will document ecologic and diagenetic processes that effect the isotopic composition of shark teeth apatite. This research will evaluate the utility of fossil shark's teeth as indicators of past environments and oceans.
