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

从赤道太平洋南北样带获得的初步结果表明，该地区表层沉积物中的15N受到上覆光带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ıCO2(aq)！有证据表明，赤道太平洋沉积有机质中的13C是该参数的一个度量。这就提出了一种可能性，即沉积有机质的15N和13C可能分别记录了过去的硝酸盐和ıCO2(aq)！分布在地表水。有证据表明，赤道太平洋生产的幅度和纬度分布在冰期至间冰期的变化可能影响了全球碳循环。沉积同位素组成（- 15N和- 13C -其整体和部分）将用于重建过去160年来赤道太平洋表层水体中硝酸盐和CO2（aq）分布的变化。作为确认和描述过去生产力变化机制的一种手段。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，沉积物分析将用于重建古海洋营养物和地表水中的CO2（aq）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.