Formation and preservation of greigite (Fe3S4) in a thick sediment layer from the central South Yellow Sea. Issue 1 (22nd December 2017)

• Record Type: Journal Article
• Authors: Liu, Jianxing; Mei, Xi; Shi, Xuefa; Liu, Qingsong; Liu, Yanguang; Ge, Shulan
• Is Part Of: Geophysical journal international. Volume 213:Issue 1(2018:Apr.)
• Page Start: 135
• Page End: 146
• Publication Date: 2017-12-22
• Subjects: Sea level change -- Environmental magnetism -- Rock and mineral magnetism; Geophysics -- Periodicals; 550
• DOI: 10.1093/gji/ggx556
• Languages: English
• ISSNs: 0956-540X

Abstract

Summary: Sediments from continental shelves are sensitive to changes in both oceanic and terrestrial conditions, and, therefore, magnetic minerals in such sediments are affected strongly by depositional and diagenetic processes. Here, we investigated systematically an N-S transect of three sediment cores from the central South Yellow Sea (SYS) muddy area. Magnetic data indicate the presence of a horizontally distributed thick greigite-bearing layer. From an age model based on published magnetostratigraphy, accelerator mass spectrometry 14 C dating ages, sedimentary characteristics and foraminiferal analysis, this layer was deposited within marine isotope stages (MIS) 17–13, following an enhanced sulphidic period over MIS 21–19 when the YS Warm Current and the associated YS Cold Water Mass were strong and where underlying sediments have higher total organic carbon, total sulphur and trace element molybdenum contents. Trace element cadmium enrichment in the greigite-bearing layers is documented for the first time, which indicates that weakly sulphidic (i.e. with trace levels of free H2 S) conditions existed before greigite formed in a sulphidic environment during early diagenesis. It also indicates that subsequent conditions free of oxygen and H2 S after greigite formation are more favourable for its preservation. We propose that organic matter supply was controlled over an extended period by moderate primary productivity. The combined effects of palaeoclimate and local tectonic subsidence were crucial for the formation and preservation of the identified greigite. In brief, our study improves understanding of the formation and preservation mechanisms of greigite in continental shelf sediments and reveals mid-Pleistocene palaeoenvironmental changes in the SYS.