CARBON AND OXYGEN STABLE ISOTOPES IN CRETACEOUS OSTRACODS: METHODOLOGY, APPLICATIONS AND CHALLENGES. Ostracods are important carbonate microfossils in stable isotope study because they occur in different aquatic environments and their carapaces calcify rapidly. The carbon isotopes provide information about paleoproductivity and availability of nutrients in oceans and lakes. Oxygen isotopes are used to estimate paleotemperature and paleosalinity existing in a sedimentary basin, over geologic time. To date, the isotopic analysis on ostracods carapaces are carried out mainly in Cenozoic material, with few researches conducted for Mesozoic. This technique is widely used on ostracods of non-marine environments and used with wariness in transitional and marine environments, where the carapaces composition will be similar to carbonate rock that contains it. This article includes concepts of stable isotopes, the analytical technique used, carrying out analysis on ostracods and interpretation of results in paleoenvironmental studies, and proposes a research protocol considering the difficulties of sampling and application in material from Cretaceous.
