(Table 1) Trace element/Ca ratios of Orbulina universa shells from late Neogene Mediterranean samples

A Mediterranean composite sedimentary record was analyzed for Ba/Ca ratios on carbonate shells of Orbulina universa planktonic foraminifer (Ba/Ca)carb providing the opportunity to study and assess the extent of freshwater inputs on the basin and possible impacts on its dynamics during the Tortonian to Recent period. A number of scanning electron microscope analyses and auxiliary trace element measurements (Mn, Sr, and Mg), obtained from the same samples, exclude important diagenetic effects on the studied biogenic carbonates and corroborate the reliability of (Ba/Ca)carb ratios in foraminifera calcite as indicators of seawater source components during the studied interval. A long-term trend with (Ba/Ca)carb values shifting from ~7 to 3 µmol/mol from the base of the Tortonian to the top of the Messinian is observed. The interval of the late Messinian salinity crisis, where biogenic carbonates are missing or strongly diagenized, represents a crucial passage not monitored in our record. At the base of the Pliocene, up to about 4.7 Ma, the (Ba/Ca)carb record shows a decreasing trend from ~4 µmol/mol stabilizing itself to an about constant value of 0.9 ± 0.3 µmol/mol for the whole Plio-Pleistocene interval. These results suggest a dramatic change in the continental runoff values, up to ~3-16 times higher during part of the late Neogene (Tortonian-early Pliocene), with a possible profound modification in the physical dynamics of the Mediterranean basin. First-order mass balance equations used to estimate barium and salinity budgets in the Mediterranean Sea during the late Miocene-early Pliocene interval support the hypothesis of an active connection of the basin with the Paratethys region and of a definitive restriction at the base of the Pliocene after about 0.7 Ma from the well-known Messinian Lagomare phase. They also open intriguing scenarios on possible circulation shifts during the Neogene.

本研究对地中海复合沉积记录中普林虫（Orbulina universa）浮游有孔虫碳酸盐壳的钡钙比（Ba/Ca）carb展开分析，为探究托尔顿期至现代期间淡水输入对该盆地的影响范围及其对盆地动力学的潜在作用提供了契机。通过对相同样品进行的多次扫描电子显微镜（scanning electron microscope）分析及辅助微量元素（锰、锶、镁）测定，排除了成岩作用对所研究生物成因碳酸盐的显著影响，并证实了研究时段内有孔虫方解石中（Ba/Ca）carb比值作为海水源组分指示剂的可靠性。观测到自托尔顿期初至墨西拿期末，（Ba/Ca）carb值呈现从约7降至3微摩尔每摩尔的长期趋势。晚墨西拿盐度危机期间，生物成因碳酸盐缺失或遭受强烈成岩作用，这一关键时段未在本记录中得到监测。上新世初期至约470万年前，（Ba/Ca）carb记录呈现从约4微摩尔每摩尔下降的趋势，并在上新世-更新世整个时段内稳定在约0.9±0.3微摩尔每摩尔的恒定值。这些结果表明，晚新近纪（托尔顿期-上新世早期）部分时段的大陆径流值发生了显著变化，其数值最高可达现代的3-16倍，这可能对地中海盆地的物理动力学产生了深远影响。利用一阶质量平衡方程估算晚中新世-上新世早期地中海的钡与盐度收支，结果支持以下假说：该盆地与副特提斯区域（Paratethys region）曾存在活跃连通，且在著名的墨西拿浅水期（Messinian Lagomare phase）之后约70万年的上新世初期，这种连通性发生了明确阻隔。这些结果还为新近纪期间可能发生的环流变化提供了引人深思的研究方向。