Continental-scale carbonate sedimentation and environmental correlates of the Shuram-Wonoka excursion

Strata of the Ediacaran Period record many Earth-Life features that distinguish the Neoproterozoic-Phanerozoic transition. However, it is difficult to determine cause and effect relationships between Ediacaran events. Here we focus on quantitative properties of carbonate rock area, volume, geochemistry, and depositional environments from the North American Ediacaran System. Patterns of carbonate sedimentation and geochemistry are broadly coincident with transgressive/regressive cycles which have been linked to glacioeustacy and global/regional tectonic forcings of Gondwana amalgamation, continent-facing subduction, and late-stage Rodinia rifting. Highly negative carbonate carbon isotope values distinguishing the Shuram-Wonoka carbon isotope excursion (SW-CIE) coincide with a marked increase in carbonate quantity (>55–60 % dolostone), which spans nearshore, outer shelf, and slope/basin depositional environments. This increase in the extent of carbonate sedimentation on the continent likely indicates marine transgression and appears to be stratigraphically bounded by glacially influenced strata associated with the Gaskiers and the Luoquan/Hankalchough glaciations. This same increase in carbonate sedimentation is also broadly coincident with the first occurrences of the Ediacaran biota. A subsequent pulse in carbonate rock quantity in the latest Ediacaran, dominantly deposited in nearshore environments, coincides with the appearance of biomineralizers, potentially indicating common cause drivers for the extent of shallow marine shelves, carbonate sedimentation, and macroevolution. A comprehensive macrostratigraphic framework for the Ediacaran provides a temporally, spatially, and environmentally explicit context for major biological and geochemical episodes and serves as a platform for future hypothesis testing at the dawn of animal life.