Tracing glacial-interglacial water mass changes in the Gulf of Corinth (IODP Expedition 381) using iron-sulphur geochemistry and magnetic susceptibility
Tracing glacial-interglacial water mass changes in the Gulf of Corinth (IODP Expedition 381) using iron-sulphur geochemistry and magnetic susceptibility
复制标题
利用铁硫地球化学和磁化率追踪科林斯湾冰期-间冰期水量变化（IODP Expedition 381）
DOI：
10.1016/j.margeo.2022.106801
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发表时间：
2022
期刊：
影响因子：
2.9
通讯作者：
Mahoney C
中科院分区：
文献类型：
--
作者：
Mahoney C
科林斯湾是一个快速裂谷盆地，由于第四纪全球海平面波动，它时而与地中海相连，时而与地中海隔绝。最近从科林斯湾（Gulf of Corinth）获得的沉积物记录（IODP Expedition 381）显示了磁化率的变化，孤立/冰川沉积物的磁化率相对较高且变化较大，而连接/间冰期沉积物的磁化率较低且更稳定。利用地球化学方法发现，形成磁化率模式的不是磁性矿物的主要输入，而是成岩作用。易还原的硫化物（最有可能是灰长岩）在高磁化率（孤立/冰川）沉积物中增加，而磁铁矿与磁化率没有系统的关系。在排除了灰长岩形成和保存的几个可能原因（底层水氧化还原条件、高沉积速率、活性铁和有机物可用性）之后，科林斯湾在孤立/冰期的硫酸盐浓度下降是最可能的解释，支持了水柱变新鲜的平行微化石证据。这种硫酸盐限制似乎使沉积黄铁矿的形成在铁磁性单硫化物（如灰长岩）阶段停滞不前。在其他沉积环境中（如切萨皮克湾、波罗的海、中新世帕拉特提斯和黑海）也观察到灰长岩形成作为古盐度变化的指示物，这支持了我们的解释。具体到科林斯湾，将盆地连通性的代理与超过75万年的高分辨率（至少40年，最高可达7年的时间分辨率）磁化率记录联系起来，为详细研究该裂谷盆地的构造演化及其与全球海平面波动的联系提供了机会。
The Gulf of Corinth is a rapidly rifting basin that has been alternately connected to/isolated from the Mediterranean due to Quaternary global sea levels fluctuations. A recently retrieved sediment record from the Gulf of Corinth (IODP Expedition 381) shows variations in magnetic susceptibility, with relatively higher and more variable values in isolated/glacial sediments and lower, more stable values in connected/interglacial sediments. Using geochemical methods, we find that not the primary input of magnetic minerals, but diagenetic processes generated the magnetic susceptibility pattern. Easily reducible sulphides (most likely greigite) increase in high magnetic susceptibility (isolated/glacial) sediments, whilst magnetite shows no systematic relationship to magnetic susceptibility. After discounting several possible causes for the formation and preservation of greigite (bottom water redox conditions, high sedimentation rates, reactive Fe and organic matter availability), a decrease in sulphate concentrations in the Gulf of Corinth during isolated/glacial periods is the most likely explanation, supporting parallel microfossil evidence for a freshening of the water column. This sulphate limitation appears to stall sedimentary pyrite formation at the stage of ferrimagnetic monosulphides like greigite. Greigite formation as an indicator of paleosalinity variations has been observed in other depositional settings (e.g., Chesapeake Bay, the Baltic Sea, the Miocene Paratethys and the Black Sea), supporting our interpretation. Specific to the Gulf of Corinth, linking a proxy for basin connectivity to a high resolution (at least 40, and up to 7 year temporal resolution) magnetic susceptibility record over 750,000 years offers an opportunity to investigate, in detail, the tectonic evolution of this rift basin and its link to global sea level fluctuations.