(Table 1) Age control points of ODP Site 160-968@en

The astronomical timescale of the Eastern Mediterranean Plio-Pleistocene builds on tuning of sapropel layers to Northern Hemisphere summer insolation maxima. A 3000-year precession lag has become instrumental in the tuning procedure as radiocarbon dating revealed that the midpoint of the youngest sapropel, S1, in the early Holocene occurred approximately 3000 years after the insolation maximum. The origin of the time lag remains elusive, however, because sapropels are generally linked to maximum African monsoon intensities and transient climate modeling results indicate an in-phase behavior of the African monsoon relative to precession forcing. Here we present new high-resolution records of bulk sediment geochemistry and benthic foraminiferal oxygen isotopes from ODP Site 968 in the Eastern Mediterranean. We show that the 3000-year precession time lag of the sapropel midpoints is consistent with (1) the global marine isotope chronology, (2) maximum (monsoonal) precipitation conditions in the Mediterranean region and China derived from radiometrically dated speleothem records, and (3) maximum atmospheric methane concentrations in Antarctica ice cores. We show that the time lag relates to the occurrence of precession-paced North Atlantic cold events, which systematically delayed the onset of strong boreal summer monsoon intensity. Our findings may also explain a non-stationary behavior of the African monsoon over the past 3 million years due to more frequent and intensive cold events in the Late Pleistocene.东地中海上新世-更新世（Plio-Pleistocene）天文年代标尺，建立于将腐泥层（sapropel layer）调谐至北半球夏季日照辐照度极大值的基础之上。3000年的岁差滞后现象在该调谐流程中发挥了关键作用：放射性碳测年结果显示，早全新世最年轻的腐泥层S1的中点，出现在日照辐照度极大值之后约3000年。然而，该时滞的成因至今仍不明确——腐泥层通常与非洲季风强度峰值存在关联，而瞬态气候模拟结果则表明，非洲季风的变化相对于岁差强迫呈同相特征。本文基于东地中海大洋钻探计划（Ocean Drilling Program, ODP）968站位的沉积物样品，报道了全新的高分辨率全样沉积物地球化学与底栖有孔虫氧同位素记录。研究证实，腐泥层中点的3000年岁差时滞与以下三项结果相一致：(1) 全球海洋同位素年代学；(2) 经放射性测年的石笋（speleothem）记录所揭示的地中海区域与中国的季风性降水峰值条件；(3) 南极冰芯记录的大气甲烷浓度峰值。研究还发现，该时滞与岁差驱动的北大西洋冷事件的发生存在关联，这类冷事件系统性地延迟了强北半球夏季风的启动时间。此外，本研究结果还可解释过去300万年间非洲季风的非稳态变化特征——这一现象与晚更新世愈发频繁且强度更高的北大西洋冷事件密切相关。