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首页> 外文期刊>Palaeogeography, Palaeoclimatology, Palaeoecology: An International Journal for the Geo-Sciences >Patterns of organic carbon and nitrogen isotopic compositions of latest Pliocene sapropels from six locations across the Mediterranean Sea
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Patterns of organic carbon and nitrogen isotopic compositions of latest Pliocene sapropels from six locations across the Mediterranean Sea

机译：地中海沿岸六个地点的最新上新世腐殖质的有机碳和氮同位素组成

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Inter-layered in the organic-poor sediments that comprise most of the sedimentary record of the Mediterranean Sea are organic-rich sapropels that represent periods of wetter climate, increased primary productivity, and suboxic to anoxic conditions at depth. In order to explore processes important in the spatial and temporal variability of sapropel-forming conditions, we selected sedimentary sequences containing two latest Pliocene sapropels at ODP Sites 974 and 975 in the western basin, the Vrica Plio-Pleistocene type-section, and ODP Sites 964, 967, and 969 in the eastern basin. Our main tools are nitrogen and organic carbon isotopes, which are diagnostic of changes in nutrient origins and availability and in primary productivity. Extremely low delta N-15 values (to -5.1 parts per thousand) indicate high rates of nitrogen fixation during sapropel formation stimulated by nearly complete consumption of nitrate in the water column due to exceptionally high rates of denitrification. Interruptions in sapropels represent brief intervals of low productivity and diminished nitrogen fixation. The geographical distribution of the interruptions and the presence of spatial patterns in TOC contents, C-org/N-tot ratios, and delta N-15 values suggest a central role of the eastern basin in initiating sapropel formation. The eastern Mediterranean evidently experienced higher rates of primary productivity during sapropel deposition and probably more intense dysoxic conditions in the water column. Organic carbon isotopes present an intriguing geographic trend across the eastern Mediterranean that is probably related to non-biological processes including variations in water temperature, salinity, and amounts of local fluvial runoff. (c) 2005 Elsevier B.V. All rights reserved.
机译：在构成地中海大部分沉积记录的贫有机沉积物中，夹杂着富含有机物的腐殖质，这些有机质代表了较湿润的气候时期，增加的初级生产力以及深度上的低氧至缺氧条件。为了探索对形成prop石条件的空间和时间变化具有重要意义的过程，我们在西部盆地的ODP站点974和975，Vrica上更新世类型剖面和ODP站点中选择了包含两种最新的上新世腐殖质的沉积层序。东部盆地的964、967和969。我们的主要工具是氮和有机碳同位素，可诊断营养物来源，可用性和初级生产力的变化。极低的δN-15值（至-5.1千分之一）表明，由于反硝化率极高，水柱中几乎完全消耗了硝酸盐，在腐殖质形成过程中固氮率很高。腐殖质中的中断代表低生产率和固氮减少的短暂间隔。中断的地理分布以及TOC含量，C-org / N-tt比和N-15增量值的空间格局的存在表明，东部盆地在开始腐殖质形成中起着核心作用。地中海东部显然在腐泥沉积过程中经历了较高的初级生产力，并且在水柱中可能出现了更强烈的缺氧条件。在整个东地中海，有机碳同位素呈现出有趣的地理趋势，这可能与非生物过程有关，包括水温，盐度和局部河流径流量的变化。 （c）2005 Elsevier B.V.保留所有权利。

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