251-1 Lithium isotope constraints on terrestrial clay formation during the Ediacaran–Cambrian transition

Session: Phanerozoic Earth System Shifts in the Marine Sedimentary Record

Presenting Author:

Tian Gan

Authors:

Gan, Tian¹, Doerrler, Andrew D.², Gilleaudeau, Geoffrey J. ³, Bykova, Natalia⁴, Marusin, Vasiliy⁵, Kochnev, Boris⁶, Hathaway, Aiden⁷, Pedersen, Matthew G.⁸, Ivanova, Natalia A. ⁹, Grazhdankin, Dmitriy V. ¹⁰, Kaufman, Alan J¹¹

(1) Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, Virginia, USA; Department of Geology, University of Maryland-College Park, College Park, MARYLAND, USA, (2) University of Maryland-College Park, College Park, MARYLAND, USA, (3) George Mason University, Fairfax, Virginia, USA, (4) University of Missouri, Columbia, MO, USA; Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, Russia, (5) Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia, (6) Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia, (7) University of Maryland, College Park, MD, USA, (8) University of Maryland, College Park, USA, (9) Geophysics and Mineral Raw Materials, Novosibirsk, Russia, (10) Trofimuk Institute of Petroleum Geology and Geophysics, Novosibirsk, USA, (11) University of Maryland, College Park, USA,

Abstract:

The Ediacaran–Cambrian transition represents a crucial period in Earth’s history, marked by global tectonic reorganization, potential glaciation, and sea level fall leading to the widespread development of marine evaporites, as well as the demise of the enigmatic Ediacara biota and rise of early metazoans during the Cambrian Explosion. Redox fluctuations across this transition have been linked to faunal turnover, which may be related to changes in organic carbon burial rates, but the driving force(s) associated with the wax and wane of organic burial fluxes remain unclear. Here, we present new lithium isotope data from three marine carbonate sections of the northern Siberian Platform that record a profound rise in δ⁷Li values (up to 32‰) associated with the BACE event. Petrographic and geochemical screening suggest that the upward trend in carbonates reflects that of contemporaneous seawater. Mass-balance modeling and geochemical constraints suggest that this rise in seawater δ⁷Li cannot be explained by local alteration or evaporite-associated sinks. Instead, we interpret it as reflecting a global change in the continental weathering regime from more congruent weathering throughout much of the Precambrian to more incongruent weathering, linked to intensified clay formation on land. The onset of the terrestrial “clay mineral factory” could have enhanced the efficiency of organic carbon burial through clay-organic matter complexation, supporting at least transient and heterogeneous oxygenation of Earth’s surface environment. Our findings reveal a fundamental link between clay formation, ocean chemistry, and biospheric evolution at the dawn of the Phanerozoic.

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

doi: 10.1130/abs/2025AM-10962

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