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GSA Connects 2024 Meeting in Anaheim, California

Paper No. 3-7
Presentation Time: 10:15 AM

INTENSE CONTINENTAL CHEMICAL WEATHERING DURING THE EDIACARAN SHURAM EXCURSION


GAN, Tian, State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550081, China; Department of Geology, University of Maryland, 8000 Regents Dr, College Park, MD 20742; Dept. of Atmospheric, Oceanic, and Earth Sciences, George Mason University, 4400 University Drive, Fairfax, VA 22030, GILLEAUDEAU, Geoffrey J., 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, MAXIMENKO, Vadim, Trofimuk Institue of Petroleum Geology and Geophysics, Novosibirsk, Russian Federation, GRAZHDANKIN, Dmitriy, Russian Academy of Science, Novosibirsk Branch, Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, 630090, Russia, XIAO, Shuhai, Department of Geosciences, Virginia Tech, Blacksburg, VA 24061 and KAUFMAN, Alan J., Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742; Geology, University of Maryland-College Park, College Park, MD 20740

Amidst the Neoproterozoic Era, the Ediacaran Shuram Excursion represents a pivotal global negative carbon isotope anomaly, aligning with significant evolutionary developments. However, the driving mechanisms of the Shuram Excursion remain uncertain, including the debate over whether a pulsed increase in continental weathering introduced oxidants to the oceans, leading to the oxidation of a substantial 12C-rich dissolved organic carbon pool. This research utilizes lithium isotope (δ7Li) measurements from well-preserved carbonate samples in Central Siberia and South China to assess the intensity and nature of continental weathering during the Shuram Excursion. Our analyses indicate nearly crustal δ7Li values (~3–5‰) in carbonate, in stark contrast to modern carbonate δ7Li values (>20‰), suggesting that the Shuram Excursion was characterized by enhanced congruent weathering with an unusual influx of low riverine δ7Li and muted fractionation during lithium removal. This enhanced weathering likely increased the flux of nutrients and oxidants to the oceans, facilitating oceanic oxygenation and accelerating the expansion of early metazoan life. Additionally, these geochemical shifts are associated with rapid deposition of authigenic clays and highly increased alkalinity, influencing marine carbonate chemistry. The findings illustrate that intensified continental weathering during the Shuram Excursion had profound effects on ocean chemistry, thereby catalyzing crucial biological transitions and ecosystem evolutions. This study determines that increased continental weathering was instrumental in promoting oceanic and atmospheric oxygenation, pivotal for the rise of complex animal life. Through illuminating the drivers of these transformative periods, our work significantly enhances the understanding of Earth’s biogeochemical cycles and their role in the evolution of life, emphasizing the critical link between geological processes and biological innovations.

Session No. 3

T33. Advances in Nontraditional Stable Isotope Measurements and Utility as Proxies in Modern and Paleo-Settings
Sunday, 22 September 2024: 8:00 AM-12:00 PM
207A (Anaheim Convention Center)
Geological Society of America Abstracts with Programs. Vol. 56, No. 5
doi: 10.1130/abs/2024AM-404983
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