Continental-Scale Carbonate Sedimentation and Environmental Correlates of the Shuram-Wonoka Excursion

Daniel Christian Segessenman , Shanan E Peters 

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. Continental-scale patterns of sedimentation have been used as proxies to investigate controls on Phanerozoic macroevolution, including sea level drivers and potential carbon cycling perturbations. 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 tectonics. Highly negative carbonate carbon isotope values distinguishing the Shuram-Wonoka carbon isotope excursion (SW-CIE) coincide with a distinct increase in carbonate quantity, which spans nearshore, outer shelf, and slope/basin depositional environments. An increase in the extent of carbonate sedimentation on the continent may indicate global marine transgression, suggesting that the excursion occurred during an interglacial warm period. This same increase in carbonate sedimentation is also broadly coincident with first occurrences of the Ediacaran biota. A subsequent increase 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 shelves, carbonate sedimentation on the continents, and macroevolution. This analysis provides a robust, rock record-based chronostratigraphic framework within which major Ediacaran events can be anchored, new evidence of environmental correlates for several key features of the Ediacaran and provides a foundation for future hypothesis testing during the dawn of animal life.