Sapropel S1 in the eastern Mediterranean Sea

Slowly accumulated (<5 cm/kyr) and rapidly accumulated (5-20 cm/kyr) sediments have been compared to define the initiation and termination times of the most recent sapropel (S1) in the eastern Mediterranean Sea. The Ba/Al ratio has been employed as a more persistent index of productivity than Corg. Accelerator mass spectrometry radiocarbon dating of pelagic foraminifera indicates a maximum duration for increased Ba/Al levels in Sl from ~9500-6000 (uncorrected radiocarbon convention years B.P.) in the rapidly accumulated sediments and ~ 9500-5300 years B.P. in the slowly accumulated sediments. This difference is ascribed to bioturbation affecting the slower accumulated Sl sediments. In the two most rapidly accumulated Sl units, from the Adriatic and Aegean Seas, there is a 'saddle' of lower values centered on 7500 years B.P. in the Corg and Ba/Al profiles, so that the visual Sl unit appears as a doublet. Geochemical evidence indicates that this intervening period is best interpreted as an episode of increased ventilation and bottom water oxygenation during the period of sapropel accumulation.

通过对比慢速沉积（<5厘米/千年）和快速沉积（5-20厘米/千年）的沉积物，确定了地中海东部最近的腐泥（sapropel）层（S1）的起始和终止时间。钡铝比（Ba/Al ratio）被用作比有机碳（Corg）更持久的生产力指标。远洋有孔虫（pelagic foraminifera）的加速器质谱放射性碳测年法（Accelerator Mass Spectrometry Radiocarbon Dating）结果显示，快速沉积沉积物中S1的钡铝比升高持续时间最长约为9500-6000年前（未校正的放射性碳常规年，BP），而慢速沉积沉积物中则为约9500-5300年前（BP）。这种差异归因于生物扰动（bioturbation）对慢速沉积的S1沉积物的影响。在来自亚得里亚海和爱琴海的两个沉积速率最快的S1单元中，有机碳和钡铝比剖面在7500年前（BP）处存在一个以低值为中心的“鞍部”，因此视觉上S1单元呈现为双峰结构。地球化学证据表明，这段间隔期最适合解释为腐泥沉积期间通风增强和底层水氧化的事件。