Formation and paleoclimatic interpretation of a continuously laminated Sapropel S5: A window to the climate variability during the Eemian interglacial extreme in the Eastern Mediterranean

腐殖层广泛存在于地中海东部盆地，对高、低纬气候交界处过去的气候变异性以及生物生产、底层水缺氧和加强有机质保存之间的相互作用进行了大量研究。利用层状切片对腐殖层形成过程中的机制和环境的了解，提供了对生产力的定量估计和关于这些过程的最高时间分辨率，但仍然受到少数不完整、只有部分层状间隔可用的限制。在这里，我们建议研究一套完整的、富含硅藻的、连续叠层的伊米亚期(~119-124Kyr BP)S5腐泥岩剖面。将使用树脂浸渍切片和冷冻切片上的连续XRF扫描、电子显微镜成像(二次和背向散射电子)和地球化学微观分析(能量色散X射线分析)技术，以确定单个薄板的组成，并在每年至百年的时间尺度上量化它们的间距和频率。本研究将提供详细资料，说明层片的形成、生产力变化的性质和规模，以及影响伊米亚极端温暖时期S5沉积的可能旋回和事件的年表。这些结果还将有助于限制过去地质时期海洋缺氧事件(OAEs)期间黑色页岩的形成，那里的记录受到成岩过程的影响。此外，我们将能够从地中海连续层压硅藻质腐蚀剂的角度，测试硅藻席形成模型作为硅出口和碳排放生物泵的重要“功能类型”。

Sapropelic layers are widespread in the Eastern Mediterranean Basin and have been subject to numerous studies on past climatic variability at the interface between high- and low-latitude climates, and on the interplay between biological production, bottom-water anoxia, and enhanced organic matter preservation. Knowledge on mechanisms and environment during the sapropel formation from laminated sections, providing quantitative estimates of productivity and highest temporal resolution on these processes, is still limited by the small number of incomplete, only partially laminated intervals available. Here, we propose to study a suite of complete, diatom-rich, continuously laminated (varved) sections of sapropel S5 of the Eemian period (~119-124 kyr BP). Continuous XRF-scanning, electron microscopic imagery (secondary and backscatter electron) and geochemical microanalysis (energy-dispersive X-ray analysis) techniques on resin-impregnated and frozen sections will be used to identify the composition of individual laminae and to quantify their spacing and frequency on annual to centennial timescales. The present study will provide detailed information on the lamina formation, on the nature and the scales of productivity variability, and on the chronology of possible cycles and events affecting the S5 deposition during the extreme warmth of the Eemian period. These results will also help to constrain the formation of black-shales in the geological past during oceanic anoxic events (OAEs), where records are affected by diagenetic processes. Further, we will be able to test the model of diatom mat formation as an important “functional type” of the biological pump for Si export and C drawdown from the perspective of continuous laminated diatomaceous sapropels in the Mediterranean.