Constraints on the nature of the Marinoan glaciation: Cyclic sedimentary records from the Nantuo Formation, South China

• Published in: Journal of Asian earth sciences 2020-03, Vol.189, p.104137, Article 104137
• Main Authors: Yan, Bin, Shen, Weibing, Zhao, Nina, Zhu, Xiangkun
• Format: Article
• Language: English
• Subjects: Episodic glacial evolution; Marinoan glaciation; Nantuo formation; South China
• ISSN: 1367-9120; 1878-5786
• DOI: 10.1016/j.jseaes.2019.104137

•Both massive diamictite and sandstone/mudstone deposits are observed in the Nantuo Formation.•Two ice advance-retreat sedimentary cycles were identified in the Nantuo Formation.•During the Nantuo glaciation, climate, sea level and sedimentary environment evolution may be closely related.•The Marinoan glaciation may be characterized by episodic evolution rather than monotonous ice-covered evolution. Detailed sedimentological investigations of the Cryogenian glacial deposits are critical for constraining the true nature of the Sturtian and Marinoan glaciations. The entire succession of the Nantuo Formation, which corresponds to the Marinoan glaciation, is well developed in South China. Here a detailed lithological and sedimentological analysis of two cores of the Nantuo Formation in Guizhou, South China, is presented in which two continuous ice advance–retreat cycles are identified. The base consists of a massive diamictite lithofacies that is representative of glacier-dominated subaqueous debris flow deposits. These proximal glaciomarine deposits are overlain by a gravel-free sandy mudstone lithofacies that is lacking in diamictites, which implies distal glaciomarine deposits. This ice advance–retreat sedimentary cycle is overlain by a weakly laminated diamictite lithofacies, which represents subaqueous debris flow deposits that formed during the second episode of ice advance. These proximal glaciomarine deposits are overlain by an interbedded sandstone–mudstone lithofacies, which is indicative of distal glaciomarine deposits that formed during another episode of ice retreat. These sedimentary cycles imply that the climate switched twice from relatively warm to extremely cold and back during the Marinoan glaciation. The global sea-level and sedimentary environments fluctuated in response to these climate changes. This co-evolution of the climate, sea-level, and sedimentary environments, which is represented by the lithofacies and sedimentary sequence of the Nantuo Formation, as well as the corresponding strata of other sections worldwide, suggests that the Marinoan glaciation is characterized by a progressive and dynamic course.