Large and rapid salinity fluctuations affected the eastern Mediterranean at the Tortonian–Messinian transition

IF 2.6 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Palaeogeography, Palaeoclimatology, Palaeoecology Pub Date : 2024-10-30 DOI:10.1016/j.palaeo.2024.112568

Evangelia Besiou , Iuliana Vasiliev , George Kontakiotis , Konstantina Agiadi , Katharina Methner , Andreas Mulch , Wout Krijgsman , Assimina Antonarakou

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Abstract

Restricted marine basins are highly sensitive to climatic fluctuations, yet, paleoenvironmental responses to gateway restriction frequently remain unclear. Here, we investigate the Mediterranean Sea that experienced gradually restricted conditions starting during the late Tortonian and culminating with complete isolation from the Atlantic during the peak of the Messinian Salinity Crisis. We established sea surface temperature and salinity records during the Tortonian to Messinian transition (7.52–7.20 Ma) through coupled analysis of organic biomarkers and oxygen and carbon isotope ratios of planktonic foraminifera from the eastern Mediterranean basin (Potamida section, Crete Island, Greece). We further contrast these sea surface data with stable isotope records of benthonic foraminifera to identify periods of increased density-driven deterioration of bottom water ventilation in the basin. The combined results show that normal marine conditions, expressed by relatively warm (27.5 °C) Tortonian surface waters with normal salinity (38) prevailed until 7.36 Ma. The 7.36–7.32 Ma interval is characterized by pulses of increased bottom water salinity, that contrast the lasting normal salinity (39) at the sea surface, indicating strengthened water column stratification provoked by sluggish water circulation already prior to the Tortonian–Messinian boundary. A brief return to marine conditions, similar to the time prior to 7.36 Ma, re-appeared between 7.32 and 7.31 Ma. Between 7.31 and 7.28 Ma, a rebound to enhanced stratification took place accompanied by a high-amplitude, stepwise decrease in both sea surface temperature and sea surface salinity. Ultimately, the Tortonian–Messinian boundary was characterized by lower sea surface temperature and salinity accompanied by increased salinity and/or colder bottom waters. A ∼ 10 °C cooling episode (at 7.212 Ma) highlights the regional importance of the global Late Miocene cooling event.

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在托尔托尼-梅西尼过渡时期，地中海东部受到盐度快速大幅波动的影响

受限的海洋盆地对气候波动高度敏感，然而，对门户受限的古环境反应往往仍不清楚。在此，我们对地中海进行了研究，该海域从托尔托尼晚期开始逐渐受到限制，最终在梅西尼盐度危机高峰期与大西洋完全隔绝。我们通过对地中海盆地东部（希腊克里特岛波塔米达断面）浮游有孔虫的有机生物标志物及氧和碳同位素比值的耦合分析，建立了托尔托尼至梅西尼过渡时期（7.52-7.20 Ma）的海面温度和盐度记录。我们进一步将这些海面数据与底栖有孔虫的稳定同位素记录进行对比，以确定该盆地底层水通气状况因密度增加而恶化的时期。综合结果表明，正常的海洋条件，即相对温暖（27.5 °C）、盐度正常（38）的托尔托尼亚表层海水，一直持续到 7.36 Ma。在 7.36-7.32 Ma 期间，底层水盐度呈脉冲式上升，与海面持久的正常盐度（39）形成鲜明对比，表明在托尔托尼-美西尼边界之前，由于水循环迟缓，水柱分层现象已经加强。在 7.32 至 7.31 Ma 之间，海洋条件短暂恢复，与 7.36 Ma 之前的情况相似。在 7.31 至 7.28 Ma 期间，伴随着海面温度和海面盐度的高振幅、阶梯式下降，出现了强化分层的反弹。最终，托尔托尼-梅西尼边界的特征是海面温度和盐度降低，同时盐度增加和/或底层水变冷。10 °C的降温事件（7.212 Ma）突出了全球晚中新世降温事件的区域重要性。

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来源期刊

Palaeogeography, Palaeoclimatology, Palaeoecology 地学-地球科学综合

CiteScore

5.90

自引率

10.00%

发文量

398

审稿时长

3.8 months

期刊介绍： Palaeogeography, Palaeoclimatology, Palaeoecology is an international medium for the publication of high quality and multidisciplinary, original studies and comprehensive reviews in the field of palaeo-environmental geology. The journal aims at bringing together data with global implications from research in the many different disciplines involved in palaeo-environmental investigations. By cutting across the boundaries of established sciences, it provides an interdisciplinary forum where issues of general interest can be discussed.