5:15 PM - 7:15 PM
[BCG06-P18] Seawater chemical conditions during the Snowball Earth reconstructed by carbonate rock in the Sturtian diamictite sequence in South Australia
Keywords:Neoproterozoic, Snowball Earth, carbonate rock
During the Cryogenian period, evidence supporting the Snowball Earth hypothesis includes the presence of diamictite (tillite) as glacial deposits and a cap carbonate immediately above the diamictite, which have been identified worldwide. Marine carbonates generally form in warm, shallow marine environments, but the cap carbonate is interpreted as reflecting extreme global warming caused by the greenhouse effect of CO2 accumulated in the atmosphere during the Snowball Earth interval. Since the glacial deposits during the global glaciation mainly consist of clastic tillite, it has been difficult to directly measure the chemical properties of the seawater during the glaciation. Therefore, studies have investigated the cap carbonate layer and the subsequent sediments to indirectly infer the seawater conditions during Snowball Earth.
Recently, carbonate layers interbedded within the tillite of the Nantuo Formation, a deposit during the Marinoan glaciation in South China, have been discovered in a drilling core. The carbonate layers exhibit δ13C values lower than those of the cap carbonate (~-7 ‰), which may represent the nature of dissolved inorganic carbon (DIC) in the ocean during the global glaciation. However, research on carbonate layers from the Snowball Earth period has predominantly focused on Marinoan glacial deposits in South China, and studies on other regions or Sturtian glaciation remain extremely limited.
In this study, we identified carbonate layers interbedded with iron-rich layers within the diamictite sequence of the Sturtian glaciation in South Australia. We investigate sedimentary structures and microscopic features and measure carbon and oxygen isotope ratios to discuss its depositional process. Furthermore, by comparing its characteristics with those of the Marinoan deposits in South China, we focus on similarities and differences, providing new insights into the chemical environment of the ocean during the Snowball Earth.
Recently, carbonate layers interbedded within the tillite of the Nantuo Formation, a deposit during the Marinoan glaciation in South China, have been discovered in a drilling core. The carbonate layers exhibit δ13C values lower than those of the cap carbonate (~-7 ‰), which may represent the nature of dissolved inorganic carbon (DIC) in the ocean during the global glaciation. However, research on carbonate layers from the Snowball Earth period has predominantly focused on Marinoan glacial deposits in South China, and studies on other regions or Sturtian glaciation remain extremely limited.
In this study, we identified carbonate layers interbedded with iron-rich layers within the diamictite sequence of the Sturtian glaciation in South Australia. We investigate sedimentary structures and microscopic features and measure carbon and oxygen isotope ratios to discuss its depositional process. Furthermore, by comparing its characteristics with those of the Marinoan deposits in South China, we focus on similarities and differences, providing new insights into the chemical environment of the ocean during the Snowball Earth.