Carbon and Oxygen isotope equilibrium between foraminifera test and sea water, its implications for paleoceanography

点击翻译按钮获取中文摘要

1)We made a high vacuum line to extract the CO2 gas efficiently from seawater. We adopt an efficient extraction method using an ultrasonic bath after 100% phosphoric acid added to seawater. This method can extract rapidly the CO2 gas from seawater only for 6 minutes. The isotope composition of the extraction CO2 gas in each shows same value respectively.2)We participated the 11 research cruises to collect the seawater, planktonic and benthic foraminifera tests, sediments in the world wide area(around Japan, Indian Ocean, western and eastern Pacific Ocean and so on). These sample sets are closely examined for possible use as a reconstruction of isotope equilibrium between the seawater and foraminifera tests in the past.3)The seawater and its dwelling depths of three dominant spices of planktonic foraminifera(G.ruber, G.sacculifer, N.dutertrei) were measured carbon and oxygen isotope ratios using a mass spectrometry. As tentative results, the oxygen isotope ratios of the G.ruber, G.sacculifer, N.dutertrei tests are 0.45‰、0.37‰、0.12‰ lighter than that of seawater at the same depths, respectively. Furthermore, oxygen isotope ratios of the G.ruber and G.sacculifer which dwell at the same depth have same difference from that of seawater. Thus, we will be going to measure the isotope ratio between seawater and foraminifera tests at surface and bottom environments. The empirical relations between isotopic disequilibria in carbon(∂^<13>C_<foraminifera>-∂^<13>C_<DIC>) and oxygen isotopes (∂^<18>C_<foraminifera>-∂^<18>C_<DIC>) in the tests and the seawater d18O and d13C of dissolved inorganic carbon(DIC), respectively, will be induced.