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The response of water column and sedimentary environments to the advent of the Messinian salinity crisis: insights from an onshore deep-water section (Govone, NW Italy)
Geological Magazine ( IF 2.3 ) Pub Date : 2020-09-07 , DOI: 10.1017/s0016756820000874
Mathia Sabino , Francesco Dela Pierre , Marcello Natalicchio , Daniel Birgel , Susanne Gier , Jörn Peckmann

During Messinian time, the Mediterranean underwent hydrological modifications culminating 5.97 Ma ago with the Messinian salinity crisis (MSC). Evaporite deposition and alleged annihilation of most marine eukaryotes were taken as evidence of the establishment of basin-wide hypersalinity followed by desiccation. However, the palaeoenvironmental conditions during the MSC are still a matter of debate, chiefly because most of its sedimentary record is buried below the abyssal plains of the present-day Mediterranean Sea. To shed light on environmental change at the advent and during the early phase of the MSC, we investigated the Govone section from the Piedmont Basin (NW Italy) using a multidisciplinary approach (organic geochemical, petrographic, and carbon and oxygen stable isotope analyses). The Govone section archives the onset of the crisis in a succession of organic-rich shales and dolomite-rich marls. The MSC part of the succession represents the deep-water equivalent of sulphate evaporites deposited at the basin margins during the first phase of the crisis. Our study reveals that the onset of the MSC was marked by the intensification of water-column stratification, rather than the establishment of widespread hypersaline conditions. A chemocline divided the water column into an oxygen-depleted, denser and more saline bottom layer and an oxygenated, upper seawater layer influenced by freshwater inflow. Vertical oscillations of the chemocline controlled the stratigraphic architecture of the sediments pertaining to the first stage of the MSC. Accordingly, temporal and spatial changes of water masses with different redox chemistries must be considered when interpreting the MSC event.

中文翻译:

水柱和沉积环境对墨西拿盐度危机的反应:来自陆上深水剖面的见解(意大利西北部戈沃内)

在墨西拿时期,地中海经历了水文变化,最终在 5.97 Ma 前发生了墨西拿盐度危机 (MSC)。大多数海洋真核生物的蒸发岩沉积和所谓的湮灭被认为是盆地范围内高盐度随后干燥的证据。然而,MSC 期间的古环境条件仍然存在争议,主要是因为其大部分沉积记录都埋在现今地中海的深海平原之下。为了阐明 MSC 出现时和早期阶段的环境变化,我们使用多学科方法(有机地球化学、岩相学以及碳和氧稳定同位素分析)调查了皮埃蒙特盆地(意大利西北部)的 Govone 剖面。Govone 部分在一系列富含有机质的页岩和富含白云石的泥灰岩中记录了危机的开始。演替的 MSC 部分代表了危机第一阶段沉积在盆地边缘的硫酸盐蒸发岩的深水当量。我们的研究表明,MSC 的发作以水柱分层的加剧为标志,而不是建立广泛的高盐条件。化学跃层将水柱分成缺氧、密度更大、盐分含量更高的底层和受淡水流入影响的含氧上层海水。化学跃层的垂直振荡控制了与 MSC 第一阶段有关的沉积物的地层结构。因此,
更新日期:2020-09-07
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