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GSA Connects 2024 Meeting in Anaheim, California

Paper No. 56-4
Presentation Time: 2:05 PM

THE SHURAM EXCURSION: NOVEL ISOTOPIC AND BIOLOGICAL CONSTRAINTS ON AN ENDURING EDIACARAN ENIGMA (Invited Presentation)


KAUFMAN, Alan J., Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, 8000 Regents Dr, College Park, MD 20742, GAN, Tian, Department of Geology, University of Maryland, 8000 Regents Dr, College Park, MD 20742; Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, 4400 University Drive, Fairfax, VA 22030, PEDERSEN, Matthew, Geology Department, University of Maryland, College Park, 8000 Regents Drive, College Park, MD 20742, DOERRLER, Andrew, Department of Geology, University of Maryland, 8000 Regents Dr, College Park, MD 20742, PICCOLI, Philip M., Geology, University of Maryland-College Park, College Park, MD 20740, GILLEAUDEAU, Geoffrey, Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, VA 22030, NANA YOBO, Lucien, Geology and Geophysics, Texas A&M University, 3115 TAMU, College Station, TX 77843, BYKOVA, Natalia, Geological Sciences, Columbia, MO 65211, XIAO, Shuhai, Department of Geosciences, Virginia Polytechnic Institute and State University, 4044 Derring Hall, Blacksburg, VA 24061, MAXIMENKO, Vadim, Trofimuk Institue of Petroleum Geology and Geophysics, Novosibirsk, Russian Federation and GRAZHDANKIN, Dmitriy, Russian Academy of Science, Novosibirsk Branch, Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, 630090, Russia

Widespread continental collision and repeated global glaciations, likely reflecting wide oscillations in greenhouse gas concentrations, enhanced both physical and chemical weathering rates in the Neoproterozoic Era. The combination of these weathering forces may have reached a crescendo during the Shuram Excursion, a profound negative carbon isotope anomaly recognized worldwide in thick mid-Ediacaran carbonate-dominated successions. Our novel analyses of well-preserved limestones deposited at the nadir of Shuram δ13C compositions in both central Siberia and South China reveal near crustal δ7Li values, suggesting a high degree of intense congruent weathering and the rapid formation of authigenic clay in ocean sediments. This interval in central Siberia is characterized by rapid seafloor cementation and the growth of crystal fans in lower shoreface environments and preserves low δ88Sr values suggesting elevated carbonate saturation of seawater and rapid precipitation rates. High carbonate saturation may additionally explain the depletion and covariance of carbon and oxygen isotope compositions of Shuram carbonates, as well as the sudden appearance of biomineralized animal shells near the end of the oceanographic phenomenon. Multiple lines of elemental and isotopic evidence suggest widespread ocean oxygenation during the Shuram Excursion that is linked to enhanced inputs of oxidants (like sulfate) and nutrients (including phosphorous) from terrestrial weathering. The long-term elevated flux of these inputs would have stimulated shallow marine photosynthesis and organic carbon sequestration by sponge-grade animals and their presumed symbionts, analogous to sulfide oxidizing bacteria in modern sponges that concentrate phosphorous from seawater. By soaking up photosynthetic organic matter, sponge-grade animals may have promoted global oceanic ventilation, revealed in δ238U compositions of Shuram carbonates worldwide, and the rise of the soft-bodied Ediacara biota.

Session No. 56

T29. New Advances in Geobiology
Sunday, 22 September 2024: 1:30 PM-5:30 PM
208A (Anaheim Convention Center)
Geological Society of America Abstracts with Programs. Vol. 56, No. 5
doi: 10.1130/abs/2024AM-404283
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