Stable carbon and oxygen isotopes and Mg/Ca ratios of foraminifers from ODP Site 202-1241 sediments

A combination of stable isotope records and Mg/Ca temperature estimates of four different planktonic foraminiferal species from Ocean Drilling Program Site 1241 allows differentiation between temperature and salinity changes in the tropical east Pacific (TEP) upper water column during the Pliocene (~5.7-2.1 Ma). The deviation of d18O records and Mg/Ca temperature estimates from thermocline-dwelling planktonic foraminifers suggests that local changes in salinity exerted a much stronger control on Pliocene TEP upper ocean water mass signatures than previously assumed. The most pronounced Pliocene change in TEP upper ocean stratification was the shoaling of the thermocline from ~4.8 to 4.0 Ma that was possibly triggered by changes in the configuration of low-latitude ocean gateways. During this time interval, mixed-layer temperatures and salinities remained relatively constant in contrast to a pronounced temperature (~6°C) and salinity decrease at the bottom of the photic zone. This change led to a new state in the thermal structure of the TEP, as the thermocline remained relatively shallow until ~2.1 Ma.

本数据集整合了大洋钻探计划（Ocean Drilling Program）1241站位的4种不同浮游有孔虫物种（planktonic foraminiferal species）的稳定同位素记录（stable isotope records）与Mg/Ca温度估算值（Mg/Ca temperature estimates），可用于区分上新世（Pliocene，约570万至210万年前）东热带太平洋（tropical east Pacific, TEP）上层水柱的温度与盐度变化。栖息于温跃层（thermocline）的浮游有孔虫的δ¹⁸O（d18O）记录与Mg/Ca温度估算值的偏差表明，相较于此前假设，当地盐度变化对上新世东热带太平洋上层水团特征的调控强度远高于以往认知。上新世东热带太平洋上层海洋层结最显著的变化是温跃层在约480万至400万年前的变浅，这一过程可能由低纬度海洋通道（low-latitude ocean gateways）构型的变化触发。在该时段内，混合层（mixed-layer）温度与盐度相对稳定，而透光层（photic zone）底部出现了显著的温度下降（约6℃）与盐度降低。这一变化使东热带太平洋的热结构进入全新状态，直至约210万年前，温跃层都维持相对较浅的状态。