CARBON ISOTOPE FRACTIONATION IN OSTRACOD EUCYPRIS MAREOTICA FROM CULTURE EXPERIMENTS AND ITS IMPLICATION FOR PALAEOENVIRONMENT RECONSTRUCTION

Culture experiments under controlled temperatures were conducted to study the carbon and oxygen isotopic fractionation between water and ostracod shells, as well as its significance in paleoclimatic reconstructions. The carbon isotopic composition of ostracod shells is mainly controlled by the carbon-isotope of water DIC in which the shells formed. The average offsets between δ¹³C of shells and the co-existing water DIC are -0.48‰,-0.59‰ and 0.7‰ for culture temperature 10℃, 15℃and 19℃ respectively. Our experiments show that temperature is probably not a significant factor controlling the carbon isotopic fractionation between ostracod shells and DIC. However, the carbon fractionation factors of E. mareotica are very close to those of the synthetic inorganic calcite formed in isotopic equilibrium with the increase in water pH. So, the carbon isotopic fractionation of different species living in different water environment should be considered, if the measurements of ¹³C/¹²C ratios of non-marine ostracod valves are used in palaeoenvironmental reconstruction.