Coccolithophorid-based geochemical paleoproxies

摘要: Coccolithophores are the only marine organisms that provide indicators of past climatic and oceanographic conditions from both organic (molecular fossils or biomarkers) inorganic (calcium carbonate) remains in sediments. The under-saturation ratio alkenone biomarkers (U37 K) provides information about sea surface temperatures is gaining widespread use as a paleotemperature proxy, particularly Quaternary sediment record. carbon isotopic fractionation (ealkenone) should allow reconstruction dissolved atmospheric CO2 concentrations if independent proxies able to consistently constrain nutrient growth rate influence on fractionation. Sr/Ca coccolith carbonate most developed proxy elemental chemistry coccoliths. Recent culture field studies suggest has potential an indicator nutrient-stimulated coccolithophorid rates. In contrast, while Mg/Ca coccoliths probably controlled by temperature, formidable challenges removing noncarbonate sources Mg fractions will preclude for paleother-mometry. Similar cleaning also Cd, Ba, V, U. Stable measurements coccolith-dominated bulk have been widely used infer temperature changes cycle Mesozoic Early Cenozoic, despite array nonequilib-rium “vital effects” different species. addition paleoceanographic applications, continued study stable may elucidate mechanisms acquisition As case all proxies, calibration required further improve our understanding coccolithophorid-based systems increase confidence their application.