Cenozoic sea-level relative to modern from deep-sea geochemical and continental margin records

We use published Pacific benthic foraminiferal oxygen isotope data and Mg/Ca records to derive a Cenozoic (66 Ma) global mean sea level (GMSL) estimate. This paper is novel in providing the first Pacific benthic foraminiferal oxygen isotopic splice for the entire Cenozoic, a detailed (Myr scale) sea-level record for the last 48 Ma based on the benthic foraminiferal oxygen isotopic and Mg/Ca approach (Mg/Ca records older than 48 Ma are uncertain). We use the 2012 Geological Time Scale (GTS), a 2-Myr smoothed paleotemperatures (Cramer et al., 2011) who used a low-pass filter that passes >80% of the amplitude for frequencies <0.5/Myr (wavelength >2 Myr), ramping down to <20% of the amplitude for frequencies >1.25/Myr (wavelength <0.8 Myr). We used equation 7b Cramer et al. (2011) and a simplified paleotemperature equation for benthic foraminifera T = 16.1– 4.76 [δ18Obenthic – (δ18Oseawater – 0.27)] to solve for oxygen isotopic changes of seawater. We assume that shorter term (<2 Myr) temperature changes comprise ~20% of the oxygen isotopic changes of seawater changes. The resultant oxygen isotopic changes of seawater estimate was scaled to GMSL changes using a revised seawater oxygen isotopes to sea-level calibration of 0.13‰/10 m of Winnick and Caves (2015). Because of temperature effects notable during peak Pleistocene interglacials, we iteratively fit the last interglacial cycle to known sea level during MIS5e and applied these temperatures (1.8°C) to major Middle to Late Pleistocene peak interglacials, tapering the temperature from the long term estimates for the peak interglacials using a Gaussian filter. We applied an empirically correction for carbonate ion change across the Eocene-Oligocene transition, to remove an apparent warming effect of ~1.5°C; we applied their empirical correction to the sea-level curve, reducing the amplitude by 28 meters from 34.17 to 34.30 Ma.

本研究利用已发表的太平洋底栖有孔虫氧同位素数据与镁钙（Mg/Ca）比值记录，重建了新生代（Cenozoic，距今66 Ma）的全球平均海平面（GMSL）估算结果。本研究的创新性在于首次构建了覆盖整个新生代的太平洋底栖有孔虫氧同位素拼接序列，并基于底栖有孔虫氧同位素与Mg/Ca方法，建立了过去48 Ma的高精度（百万年级别）海平面记录（48 Ma之前的Mg/Ca记录存在不确定性）。本研究采用2012版地质年代学标尺（GTS），并使用Cramer等人2011年提出的2百万年平滑古温度序列：该序列采用低通滤波器（low-pass filter）处理，对频率<0.5/Myr（波长>2 Myr）的信号保留>80%的振幅，对频率>1.25/Myr（波长<0.8 Myr）的信号衰减至<20%的振幅。我们通过Cramer等人2011年的公式7b，结合简化的底栖有孔虫古温度公式：T = 16.1 – 4.76[δ¹⁸O_benthic – (δ¹⁸O_seawater – 0.27)]，求解海水氧同位素变化。我们假设短期（<2 Myr）温度变化约占海水氧同位素变化的20%。本研究将得到的海水氧同位素变化估算值，通过Winnick与Caves 2015年修订的海水氧同位素-海平面校准关系（0.13‰/10 m），换算为全球平均海平面变化。由于更新世盛间冰期存在显著的温度影响，我们将末次间冰阶与已知的海洋同位素阶段5e（MIS5e）海平面数据进行迭代拟合，并将得到的温度值（1.8°C）应用于中更新世晚期至晚更新世的主要盛间冰期，同时通过高斯滤波器将盛间冰期的温度从长期估算值中逐步衰减。我们针对始新世-渐新世过渡期（Eocene-Oligocene transition）的碳酸根离子变化进行了经验校正，以消除约1.5°C的表观增温效应；并将该经验校正应用于海平面曲线，将34.17 Ma至34.30 Ma区间的振幅降低了28米。