Late Miocene sea surface salinity variability and paleoclimate conditions in the Eastern Mediterranean inferred from coral aragonite δ18O
Late Miocene sea surface salinity variability and paleoclimate conditions in the Eastern Mediterranean inferred from coral aragonite δ18O
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从珊瑚霰石δ18O推断东地中海晚中新世海面盐度变化和古气候条件
DOI：
10.1016/j.chemgeo.2009.01.010
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发表时间：
2009
期刊：
影响因子：
3.9
通讯作者：
Iliopoulos
中科院分区：
文献类型：
--
作者：
Mertz-Kraus R;Brachert TC;Reuter M;Galer SJG;Fassoulas C;Iliopoulos
珊瑚骨骼是化学代理的档案，可以以亚年分辨率进行古环境重建。这些档案的稳定氧同位素 (δ18O) 比率反映了海面温度 (SST) 以及环境海水的 δ18O 组成。 δ18O海水组成不仅受全球冰积聚的控制，而且河流流量以及蒸发和降水的水文平衡都影响海面盐度（SSS），在边缘海也发挥着重要作用。新的亚年度解析珊瑚 δ18O 数据与克里特岛（东地中海）晚中新世珊瑚群落的已发表数据一起进行了测量和评估。这个时间窗口对于地中海的古海洋演化特别重要，因为它涵盖了连接地中海和大西洋的海洋门户的连续关闭，最终导致 5.96 Ma 的墨西拿盐度危机 (MSC) 的爆发。珊瑚是从 87Sr/86Sr 年代地层学测年的八个时间切片中回收的，覆盖约 10 至约 7 Ma 的时间窗口，以监测 MSC 前的环境变化。珊瑚礁珊瑚 Porites 和 Tarbellastraea 的氧同位素组成记录了晚中新世期间年平均 δ18O 以及平均 δ18O 季节性的显着变化。托托阶珊瑚和麦西尼亚珊瑚的年平均 δ18O 值相差高达 1.72‰，并且表现出显着的变异性。由于根据岩性、古植物学和地球化学证据，可以认为晚中新世的海表温度相当恒定，因此珊瑚的年平均 δ18O 变化似乎是由于 MSC 之前的中新世晚期的海表温度变化造成的。这一结果与早期的概念形成鲜明对比，早期的概念尽管地中海盆地从大约 9 Ma 前开始就日益孤立，但直到第一个 MSC 蒸发岩沉积前仅 300 kyr，SSS 才发生变化。与托尔托尼亚珊瑚相比，麦西尼亚珊瑚的平均季节性 δ18O 振幅低 0.4‰，这可能是由于夏季蒸发增强所致。托托阶和麦西尼亚珊瑚 δ18O 记录的光谱分析表明存在显着的年际变化，周期为 2-3 年和 4-5 年。这种变异性与现代记录中发现的相似。在现代情况下，冰岛低压和亚速尔群岛高压中心影响环地中海地区的气候。结合其他研究的证据，本研究的珊瑚记录表明，类似的压力场系统在晚中新世早期就已经存在。
Coral skeletons are archives of chemical proxies which enable paleoenvironmental reconstructions to be made at subannual resolution. Stable oxygen isotope (δ18O) ratios of these archives reflect sea surface temperature (SST) as well as the δ18O composition of ambient seawater. The δ18Oseawatercomposition is not only controlled by global ice build-up, but river discharge and the hydrological balance of evaporation and precipitation, all influencing sea surface salinity (SSS), also play an important role in marginal seas. New sub-annually resolved coral δ18O data were measured and evaluated together with published data from reef coral communities of Late Miocene age from Crete (Eastern Mediterranean). This time-window is of particular importance for the paleoceanographic evolution of the Mediterranean Sea, because it covers the successive closure of the marine gateways connecting the Mediterranean with the Atlantic Ocean, which culminated in the onset of the Messinian salinity crisis (MSC) at 5.96 Ma. Corals were recovered from eight time-slices dated by87Sr/86Sr chronostratigraphy and cover a time-window from ∼10 to ∼7 Ma to monitor pre-MSC environmental changes. The oxygen isotope composition of the reef corals Porites and Tarbellastraea document significant changes in mean annual δ18O as well as in mean δ18O seasonality during the Late Miocene. Tortonian and Messinian coral mean annual δ18O values differ by up to 1.72‰ and exhibit substantial variability. Since SSTs can be considered rather constant over the Late Miocene according to lithological, paleobotanical and geochemical evidence, the mean annual δ18O variations in the corals appear to result from changing SSS during the Late Miocene prior to the MSC. This result is in contrast to earlier concepts that, despite increasing isolation of the Mediterranean basin starting at about 9 Ma ago, SSS did not change until only 300 kyr prior to the deposition of the first MSC evaporites. Mean seasonal δ18O amplitudes are lower by 0.4‰ in the Messinian compared to those of the Tortonian corals, which may be due to enhanced summer evaporation. Spectral analyses of Tortonian and Messinian coral δ18O records indicate significant interannual variability with periods of 2–3 and 4–5 years. Such variability is similar to that found in modern records. In the modern case, the Iceland Low and Azores High pressure centers influence climate in the Circum-Mediterranean region. Combined with evidence from other studies, the coral records of this study suggest that a similar pressure field system was already in existence in the early Late Miocene.
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DOI：
10.1016/s0031-0182(99)00065-6
发表时间：
1999-09-01
影响因子：
3
作者：
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影响因子：
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DOI：
10.1016/s0031-0182(02)00612-0
发表时间：
2003
期刊：
Palaeogeography, Palaeoclimatology, Palaeoecology
影响因子：
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作者：
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DOI：
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发表时间：
2006
期刊：
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DOI：
--
发表时间：
1996
期刊：
影响因子：
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作者：
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通讯作者：
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