214-5 Global and Local Controls on North American Carbonate Sedimentation During the Ediacaran Rise of Metazoan Life

Session: The Neoproterozoic Earth and Life Co-evolution, Part II

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Rocks from the terminal Neoproterozoic Ediacaran Period record many significant changes in Earth-and life co-evolution, including the evolution of the Ediacaran biota. The Ediacaran biota’s appearance in the fossil record broadly coincides with global tectonic changes, the Shuram-Wonoka negative carbon isotope excursion (SW-CIE), and glaciations of unknown duration and extent. However, determination of direct cause-and-effect relationships between events is challenging due to a paucity of Ediacaran-age outcrops. Here we present quantitative analyses of carbonate rock area, volume, inorganic carbon isotope values, carbonate phase, and depositional environments from the Ediacaran System of North America. Ediacaran carbonate sedimentation patterns and geochemistry have been connected to continental-scale transgression/regression driven by glacioeustacy and local/global tectonic forcings associated with late-stage Rodinia rifting and Gondwana amalgamation. Extreme negative carbon isotope values of SW-CIE coincide with a major increase in carbonate quantity (>55-60% dolostone) that spans nearshore, outer shelf, and slope/basin depositional environments. This increase in carbonate sedimentation on the continent broadly coincides with the oldest known occurrences of the Ediacaran biota and seems to be bracketed by glacially influenced strata of the Gaskiers and the Luoquan/Hankalchough. Conspicuously, emplacement of the Catoctin Large Igneous Province (LIP) and evidence of a lull in Gondwana amalgamation mountain-building coincides with the SW-CIE, the appearance of the Ediacaran biota, and the carbonate quantity increase. Other lines of evidence are consistent with both increased siliciclastic and carbonate quantities during the SW-CIE, such as increased dissolved silica linked to the unique taphonomy of the Ediacara biota and primary dolomite precipitation. When combined, these lines of evidence may suggest continental weathering enhanced siliciclastic flux and alkalinity in marginal marine environments coincident with the SW-CIE. A subsequent pulse of dominantly nearshore carbonates in the latest Ediacaran coincides with the earliest known occurrences of biomineralizers, suggesting common drivers of shallow marine shelf area, carbonate quantity, and macroevolution. Our comprehensive macrostratigraphic framework of Ediacaran continental sediments appears to serve as a proxy for the effects of fluctuating glacioeustacy and local/global tectonic forcings that were instrumental in shaping Earth and life co-evolution during the latest Neoproterozoic.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10758

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