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首页> 外文期刊>Paleoceanography >Neogene ice volume and ocean temperatures: Insights from infaunal foraminiferal Mg/Ca paleothermometry
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Neogene ice volume and ocean temperatures: Insights from infaunal foraminiferal Mg/Ca paleothermometry

机译：新近纪的冰量和海洋温度：臭虫有孔虫Mg / Ca古温度计的见解

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Antarctic continental-scale glaciation is generally assumed to have initiated at the Eocene-Oligocene Transition, yet its subsequent evolution is poorly constrained. We reconstruct changes in bottom water temperature and global ice volume from 0 to 17 Ma using delta O-18 in conjunction with Mg/Ca records of the infaunal benthic foraminifer, O. umbonatus from Ocean Drilling Program (ODP) Site 806 (equatorial Pacific; similar to 2500m). Considering uncertainties in core top calibrations and sensitivity to seawater Mg/Ca (Mg/Ca)(sw), we produce a range of Mg/Ca-temperature-Mg/Ca-sw calibrations. Our favored exponential temperature calibration is Mg/Ca = 0.66 +/- 0.08 x Mg/Ca-sw(0.27 +/- 0.06) x e((0.114 +/- 0.02 x BWT)) and our favored linear temperature calibration is Mg/Ca = (1.21 +/- 0.04 + 0.12 +/- 0.004 x BWT (bottom water temperature)) x (Mg/Ca-sw -0.003 +/- 0.02) (stated errors are 2 s.e.). The equations are obtained by comparing O. umbonatus Mg/Ca for a Paleocene-Eocene section from Ocean Drilling Program (ODP) Site 690 (Weddell Sea) to delta O-18 temperatures, calculated assuming ice-free conditions during this peak warmth period of the Cenozoic. This procedure suggests negligible effect of Mg/Ca-sw on the Mg distribution coefficient (D-Mg). Application of the new equations to the Site 806 record leads to the suggestion that global ice volume was greater than today after the Middle Miocene Climate Transition (similar to 14Ma). ODP Site 806 bottom waters cooled and freshened as the Pacific zonal sea surface temperature gradient increased, and climate cooled through the Pliocene, prior to the Plio-Pleistocene glaciation of the Northern Hemisphere. The records indicate a decoupling of deep water temperatures and global ice volume, demonstrating the importance of thresholds in the evolution of the Antarctic ice sheet.
机译：一般认为，南极大陆规模的冰川作用始于始新世-渐新世过渡，但随后的演化受到的约束却很少。我们使用O-18三角洲，结合海洋钻探计划（ODP）站点806（赤道太平洋）底栖有孔虫（O. umbonatus）的Mg / Ca记录，重建了从0到17 Ma的底部水温和全球冰量的变化。类似于2500m）。考虑到核心顶部校准的不确定性和对海水Mg / Ca（Mg / Ca）（sw）的敏感性，我们产生了一系列Mg / Ca温度-Mg / Ca-sw校准。我们喜欢的指数温度校准是Mg / Ca = 0.66 +/- 0.08 x Mg / Ca-sw（0.27 +/- 0.06）xe（（0.114 +/- 0.02 x BWT）），我们喜欢的线性温度校准是Mg / Ca =（1.21 +/- 0.04 + 0.12 +/- 0.004 x BWT（底部水温））x（Mg / Ca-sw -0.003 +/- 0.02）（陈述的误差为2 se）。通过将海洋钻探计划（ODP）站点690（Weddell Sea）的古新世-始新世剖面的O.umbonatus Mg / Ca与O-18三角洲温度进行比较，可以得出方程式。新生代。此程序表明Mg / Ca-sw对Mg分布系数（D-Mg）的影响可忽略不计。将新的等式应用到806号站点记录后，得出这样的建议：中新世中期气候转变（类似于14Ma）之后，全球冰量大于今天。 ODP站点806的底部水域随着太平洋纬向海表温度梯度的增加而变凉和变新鲜，并且在北半球的上新世冰期之前，气候经过上新世而冷却。记录表明深水温度与全球冰量之间存在脱钩关系，这表明阈值在南极冰盖演化中的重要性。

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