Geological Society of America

T3 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

INTENSE CONTINENTAL CHEMICAL WEATHERING DURING THE EDIACARAN SHURAM EXCURSION

Paper number: T3-9
Program: Technical Sessions
Time: 10:15 AM – 10:30 AM

Authors

Tian Gan Presenting Author
Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou
Tian Gan Presenting Author
University of Maryland, College Park, MD
Tian Gan Presenting Author
George Mason University, Fairfax, VA
Geoffrey Gilleaudeau
George Mason University, Fairfax, VA
Matthew Pedersen
University of Maryland, College Park, College Park, MD
Andrew Doerrler
University of Maryland, College Park, MD
Vadim Maximenko
Trofimuk Institue of Petroleum Geology and Geophysics, Novosibirsk
Dmitriy Grazhdankin
Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, N/A
Shuhai Xiao
Virginia Tech, Blacksburg, VA
Alan Kaufman
University of Maryland, College Park, MD
Alan Kaufman
University of Maryland-College Park, College Park, MD

Abstract

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.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-404983

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