Use of Sedimentary Nitrogen and Carbon Isotopic Composition for Reconstruction of the Past History of the Equatorial Pacific Upwelling Region

赤道太平洋南北样带的初步结果表明，该地区表层沉积物中的&Amp；15N受上覆真光层中硝酸盐浓度的强烈影响。同样，浮游植物的碳同位素组成反映了环境的ı二氧化碳(AQ)！有证据表明，沉积有机质中的~(13)C是赤道太平洋这一参数的量度。这增加了沉积有机质&amp；15N和&amp；13C可能分别记录了过去的硝酸盐和ı二氧化碳(AQ)的可能性！地表水中的分布。有证据表明，赤道太平洋的生产量和纬度分布发生了从冰期到间冰期的变化，这可能影响了全球碳循环。沉积同位素组成(&amp；15N和&amp；13C--包括其整体和部分)将被用于重建过去160年来赤道太平洋表层水域硝酸盐和二氧化碳(AQ)分布的过去变化，作为确认和描绘这些过去生产力变化的机制的一种手段。将研究控制埋藏有机质同位素组成的水柱和早期成岩作用。此外，沉积物分析还将用于重建古海洋营养物质和表层水中二氧化碳(AQ)的分布。

Preliminary results obtained from a north-south transect in the equatorial Pacific suggest that the &15N in the surficial sediments of this region is strongly affected by the nitrate concentration in the overlying euphotic zone. Similarly, carbon isotopic composition of phytoplankton reflects ambient ıCO2(aq)! and evidence exists that &13C in sedimentary organic matter is a measure for this parameter in the equatorial Pacific. This raises the possibility that &15N and &13C of sedimentary organic matter might respectively record past nitrate and ıCO2(aq)! distributions in surface waters. There is evidence for glacial to interglacial changes in both the magnitude and latitudinal distribution of production in the equatorial Pacific that might have influenced the global carbon cycle. Sedimentary isotopic composition (&15N and &13C - both bulk and fractions thereof) will be used for the reconstruction of past changes in the distribution of nitrate and CO2(aq) in equatorial Pacific surface waters over the last 160 kyrs, as a means both to confirm and to delineate the mechanisms for these past changes in productivity. Studies will be made of water column and early diagenetic processes which control the isotopic composition of buried organic matter. Also sediment analyses will be used to reconstruct paleoceanographic nutrient and CO2(aq) distributions in surface waters.