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首页> 外文期刊>Palaeogeography, Palaeoclimatology, Palaeoecology: An International Journal for the Geo-Sciences >Geochemical and micropaleontological characterisation of a Mediterranean sapropel S5: A case study from core BAN89GCO9 (south of Crete)
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Geochemical and micropaleontological characterisation of a Mediterranean sapropel S5: A case study from core BAN89GCO9 (south of Crete)

机译：地中海腐殖质S5的地球化学和微古生物学特征：以核心BAN89GCO9（克里特岛南部）为例

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Several geochemical and micropaleontological proxies were studied in a well developed sapropel S5 from a core collected south of Crete to investigate the causes and the mechanisms of its deposition, to reconstruct the paleoenvironmental and paleoceanographical conditions at time of its formation and to detect the roles played by productivity and anoxia. The geochemical proxies are also used to unravel the sediment provenance and therefore to help tracing water circulation patterns and freshwater sources. The multiproxy approach reveals that the sapropel layer has high internal variability and five different depositional phases can be identified, four within the visible sapropel layer. An increase in temperature and the development of a Deep Chlorophyll Maximum characterise the onset of the sapropel (phase 1), with enhanced productivity being favoured by local riverine input, not clearly ascribable to Nile river freshwater discharge, and by the shoaling of the pyenoclineutricline. Surface water stratification and productivity develop, together with strong seafloor dysoxia/anoxia. Phase 2 is characterised by lower stratification, slightly lower temperature and/or higher seasonal contrast, and still high productivity. Phase 3 records high productivity, high temperature and high stratification, probably more sustained by the Nile input. A sudden partial reoxygenation takes place at the end of this phase, changing the main features of the sapropel. In the fourth phase, productivity starts to decrease, water stratification seems to be partially broken down and sediment oxygenation increases. A transitional phase (phase 5) occurs between the end of the visible sapropel and the normal pelagic post-sapropel sedimentation, where productivity is still high and oxygenation improves compared to the visible sapropel layer. The massive occurrence of Polysphaeridium zoharyi, cyst of a red tide forming dinoflagellate, also characterises this phase. The geochemical proxies indicate that pre-sapropel and post-sapropel sediments are quite different from each other, and the provenance shifts from a more mixed to a more markedly southern origin of sediments. (c) 2005 Elsevier B.V. All rights reserved.
机译：在克里特岛南部采集的一个发育良好的腐殖质S5中研究了几种地球化学和微古生物学代理，以调查其沉积的成因和机理，在其形成时重建古环境和古海洋条件，并检测其作用。生产力和缺氧。地球化学代理也可用于揭示沉积物的来源，因此有助于追踪水的循环模式和淡水源。多代理方法表明，腐殖质层具有较高的内部可变性，可以识别出五个不同的沉积相，其中四个在可见的腐殖质层内。温度的升高和深层叶绿素最大值的出现表征了腐殖土的发生（第1阶段），当地河流的投入（不明显归因于尼罗河淡水排放）和紫杉酚/营养素。地表水分层和生产力的发展，以及强烈的海底发育不良/缺氧。第2阶段的特征是较低的分层，较低的温度和/或较高的季节性对比度以及较高的生产率。第3阶段记录了高生产率，高温和高分层现象，可能由尼罗河的输入更为持久。在此阶段结束时，突然发生部分再氧化，从而改变了prop草的主要特征。在第四阶段，生产率开始下降，水的分层似乎被部分破坏，沉积物的氧合增加。过渡相（阶段5）发生在可见sa石层的末端和正常上层sa石后post石层的沉积之间，与可见sa草层相比，那里的生产率仍然很高并且氧合作用得到改善。巨球藻zoharyi，形成潮红形成囊藻的囊肿，也表明了这一阶段。地球化学指标表明，腐泥前和腐泥后的沉积物彼此之间有很大的不同，并且物源从沉积物的混合程度更高的地方转移到南部的沉积物来源更加明显。 （c）2005 Elsevier B.V.保留所有权利。

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