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Development of photic zone euxinia in the eastern Mediterranean Basin during deposition of Pliocene sapropels

机译：上新世腐殖质沉积过程中地中海东部海域光合带游隙的发展

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Carotenoids were analysed in ca. 1-cm thick subsamples of three laterally time-equivalent sapropels from a west-east transect of the eastern Mediterranean Basin to study euxinic periods during Pliocene sapropel formation. The amount of intact isorenieratene (summed all-trans and cis isomers), ranged from non-detectable at the base and top of a sapropel up to 140 mu g/g sediment in the central parts. Isorenieratene accumulation rates at the central and western site are remarkably similar and increase sharply to levels of up to 3.0 mg m~(-2) yr~(-1) in the central part of the sapropel and then drop to low levels. This pattern indicates an expansion of euxinic conditions reaching into the photic zone, followed by deepening of the chemocline during deposition of this Pliocene sapropel. The sapropel from the easternmost site of the basin, which contains less organic carbon, shows much lower isorenieratene accumulation rates and even absence of isorenieratene in the central part of the sapropel. Ba/Al ratios indicate enhanced palaeoproductivity during sapropel formation, supporting previously proposed models, according to which increased productivity is the driving force for the generation of euxinic conditions.
机译：类胡萝卜素在约。来自地中海盆地东部东西样断面的三个横向时间等效的腐殖质的1厘米厚子样本，用于研究上新世腐殖质形成过程中的富营养阶段。完整的异烯戊二烯（全反式和顺式异构体的总和）范围从腐殖质的底部和顶部无法检测到中心部分的沉积物高达140μg / g。异戊烯在中部和西部的积累速率非常相似，并且在腐殖质的中部急剧增加至最高3.0 mg m〜（-2）yr〜（-1），然后下降到较低的水平。该模式表明，在该上新世腐殖土的沉积过程中，共济失调条件的扩展到达了光化区，随后趋化线的加深。来自盆地最东端的腐殖土中有机碳含量较低，显示出异烯戊二烯的积累速率低得多，甚至在腐殖质的中部也没有异烯戊二烯。 Ba / Al比值表明在腐殖质形成过程中古生产力提高，从而支持了先前提出的模型，根据该模型，生产力的提高是产生好氧条件的驱动力。

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