Enigmatic provenance of carbonate clasts in Cryogenian glacial diamictite of the Nantuo Formation in South China

Nolan, Morrison; Xiao, Shuhai; Gill, Benjamin C.; Reid, Rachel O.; Schwid, Maxwel F.

doi:10.1016/j.precamres.2022.106734

Cited by 2 publications

(1 citation statement)

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“…It consists mainly of massive diamictites with interbedded silty mudstones and black shales (Supplementary Note 1 ). Diamictites in the Nantuo Formation contains abundant granite, gneiss, and carbonate clasts that can reach decimeters in size (mainly 5–50 cm in maximum dimension) 31 , which are distinct from diamictites of the Gucheng Formation, which contains clasts that are generally small in size (mainly 2 mm–5 cm in maximum dimension) and are derived from sandstone, vein quartz, and chert. At the Songluo section, the diamictites underlying and overlying the fossiliferous black shales are similar in clast compositions, and both contain clasts characteristic of the Nantuo Formation 23 .…”

Section: Resultsmentioning

confidence: 99%

Mid-latitudinal habitable environment for marine eukaryotes during the waning stage of the Marinoan snowball glaciation

Song

et al. 2023

Nat Commun

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During the Marinoan Ice Age (ca. 654–635 Ma), one of the ‘Snowball Earth’ events in the Cryogenian Period, continental icesheets reached the tropical oceans. Oceanic refugia must have existed for aerobic marine eukaryotes to survive this event, as evidenced by benthic phototrophic macroalgae of the Songluo Biota preserved in black shales interbedded with glacial diamictites of the late Cryogenian Nantuo Formation in South China. However, the environmental conditions that allowed these organisms to thrive are poorly known. Here, we report carbon-nitrogen-iron geochemical data from the fossiliferous black shales and adjacent diamictites of the Nantuo Formation. Iron-speciation data document dysoxic-anoxic conditions in bottom waters, whereas nitrogen isotopes record aerobic nitrogen cycling perhaps in surface waters. These findings indicate that habitable open-ocean conditions were more extensive than previously thought, extending into mid-latitude coastal oceans and providing refugia for eukaryotic organisms during the waning stage of the Marinoan Ice Age.

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Section: Resultsmentioning

confidence: 99%