Stable carbon and oxygen isotope ratios of planktonic foraminifera from the equatorial Atlantic

Carbon isotopic records of nutrient-depleted surface water place constraints on the past fertility of the oceans and on past atmospheric pCO2 levels. The best records of nutrient-depleted delta13C are obtained from planktonic foraminifera living in the thick mixed layers of the western equatorial and tropical Atlantic Ocean. We have produced a composite, stacked Globigerinoides sacculifer delta13C record from the equatorial Atlantic, which exhibits significant spectral power at the 100,000- and 41,000-year Milankovitch periods, but no power at the 23,000-year period. Similar to the record presented by Shackleton and Pisias [1985], surface-deep ocean Delta delta13C produced with the G. sacculifer record leads the delta18O ice volume record. However, the glacial-interglacial amplitudes of Delta delta13C differ between our record and Shackleton and Pisias [1985] record. […]

碳同位素记录的营养贫瘠表层水体对过去海洋肥力和过去大气二氧化碳浓度水平的演变施加了限制。营养贫瘠的δ13C最佳记录源自生活于西赤道和热带大西洋深厚混合层中的浮游有孔虫。我们已从赤道大西洋制作了一组复合叠加的Globigerinoides sacculifer δ13C记录，该记录在10万年和4.1万年Milankovitch周期上表现出显著的谱功率，但在2.3万年周期上没有功率。与Shackleton和Pisias（1985年）所呈现的记录相似，利用G. sacculifer记录产生的表层-深层海洋δ13C与δ18O冰体积记录相比，表现出领先性。然而，我们的记录与Shackleton和Pisias（1985年）记录之间的冰期-间冰期δ13C振幅存在差异。