Abstract The Messinian Salinity Crisis (MSC) was an extreme event that affected the Mediterranean Sea during the late Miocene, leading to massive evaporite deposition across the basin. Here we focus on the Perales section (Sorbas Basin, Western Mediterranean), using calcareous nannofossil (CN) and foraminiferal geochemical analyses to trace the paleoenvironmental dynamics culminating in the MSC onset. Orbital and tectonic forcing drove the CN fluctuations that correlated with the lithological quadripartite precessional cycle. Our integrated analysis reveals that cyclical sapropel deposition was triggered by an increase in marine productivity, followed by an increase in freshwater input and the development of a Deep Chlorophyll Maximum (DCM). The overlying marl records the protracted freshwater input that led to the shallowing of the DCM, decreasing organic carbon export and promoting seafloor re-oxygenation. Stratification, acting as a barrier, trapped part of the river-sourced nutrients below the photic zone. The subsequent gradual decrease in temperature promoted the disruption of the stratification, mixing nutrients upward into the photic zone and promoting diatom proliferation and preservation. When the reservoir of dissolved silica was exhausted, bioturbated marls were deposited at the top of the cycle. In the last pre-evaporitic cycle (UA34) the usual lithological cyclicity is obliterated; however the precessional footprint is revealed by CN fluctuations, suggesting that sapropel-like deposition lasted for most of the cycle. This cycle also records a succession of CN abundance peaks (MSC onset bioevent), as already recorded in several Mediterranean sections approximately at the MSC onset, suggesting that the same paleoenvironmental changes triggered the evaporitic phase in the whole Mediterranean. This bioevent marks the last step of water exchange reduction with the Atlantic (restriction pulse), which increased the sensitivity of the Mediterranean to freshwater input and associated nutrient delivery, culminating in a further increase in marine productivity.

中文翻译：

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Sorbas 盆地中的钙质纳米化石和有孔虫微量元素记录：墨西拿盐度危机开始拼图的新部分

摘要 墨西拿盐度危机（MSC）是中新世晚期影响地中海的极端事件，导致整个盆地大量蒸发岩沉积。在这里，我们关注 Perales 部分（Sorbas 盆地，西地中海），使用钙质纳米化石 (CN) 和有孔虫地球化学分析来追踪在 MSC 开始时达到高潮的古环境动力学。轨道和构造强迫驱动了与岩性四方岁差旋回相关的 CN 波动。我们的综合分析表明，周期性腐泥沉积是由海洋生产力的增加引发的，随后是淡水输入的增加和深叶绿素最大值 (DCM) 的发展。上覆泥灰岩记录了导致 DCM 变浅的长期淡水输入，减少有机碳输出并促进海底再氧化。分层作为屏障，将部分来自河流的营养物质困在透光区下方。随后温度的逐渐降低促进了分层的破坏，将营养物质向上混合到透光区，促进了硅藻的增殖和保存。当溶解的二氧化硅库耗尽时，生物扰动的泥灰岩沉积在循环的顶部。在最后一个蒸发前旋回（UA34）中，通常的岩性旋回消失了；然而，CN 波动揭示了岁差足迹，表明腐泥状沉积持续了大部分周期。该循环还记录了连续的 CN 丰度峰值（MSC 起始生物事件），正如在大约在 MSC 开始时已经在几个地中海部分记录的那样，表明相同的古环境变化触发了整个地中海的蒸发阶段。这一生物事件标志着与大西洋水交换减少的最后一步（限制脉冲），这增加了地中海对淡水输入和相关营养物质输送的敏感性，最终导致海洋生产力的进一步提高。