Implications for Ediacaran biological evolution from the ca. 602 Ma Lantian biota in China

Abstract

The morphologically differentiated benthic macrofossils of algae and putative animal affinities of the Lantian biota in China represents the oldest known Ediacaran macroscopic eukaryotic assemblage. Although the biota provides remarkable insights into the early evolution of complex macroeukaryotes in the Ediacaran, the uncertainty in its age has hampered any robust biological evaluation. We resolve this issue by applying a petrographic-guided rhenium-osmium (Re-Os) organic-bearing sedimentary unit study on the Lantian biota. This work confines a minimum age for the first appearance of the Lantian biota to 602 ± 7 Ma (2σ, including decay constant uncertainty). This new Re-Os date confirms that the Lantian biota is of early–mid Ediacaran age and temporally distinct from the typical Ediacaran macrobiotas. Our results indicate that the differentiation and radiation of macroscopic eukaryotes, and the evolution of the primitive, erect epibenthic ecosystem, occurred in the early–mid Ediacaran and were associated with highly fluctuating oceanic redox conditions. The radiogenic initial 187Os/188Os ratios derived from the Lantian (1.14 ± 0.02) and other Ediacaran shales invoke oxidative weathering of upper continental crust in the early–middle Ediacaran, which may have stimulated the evolution of life and oceanic-atmospheric oxygenation. Integrated with published Ediacaran chronological and geochemical data, our new Re-Os geochemical study of the Lantian black shale provides a refined, time-calibrated record of environment and eukaryote evolution during the Ediacaran.

A phosphate-rich marine reservoir in the redox stratified Ediacaran ocean

“…Indeed, the timing (ca. 600 Ma) of elevated phosphate concentrations recorded by the IFs analyzed herein coincides (within error) with the minimum age of the Lantian assemblage of South China (602 ± 7 Ma), which constitutes the oldest known Ediacaran macroscopic eukaryotic assemblage 45 .…”

Implications of new geochronological constraints on the Aberfeldy stratiform barite deposits, Scotland, for the depositional continuity and global correlation of the Neoproterozoic Dalradian Supergroup

“…8c). The early-mid Ediacaran differentiation and radiation of macroscopic eukaryotes was associated with highly fluctuating oceanic redox conditions and Os-i seawater values (Yang et al, 2022). We infer a single, homogenous source of osmium and by inference metals in fluids from which pyrite, or a precursor iron sulfide, precipitated.…”

Taxonomy and palaeoenvironmental distribution of palaeopascichnids

“…1). The oldest representatives of this species are found in Member 2 of the Lantian Formation in South China (Yuan et al 2011), the minimum age of which constrained to 602 ± 7 Ma (Yang et al 2022), and the youngest taxa occur in the uppermost part of the Ediacaran Zigan Formation in the South Urals, Russia , which also correlates to a similar level of the Cambrian Global Boundary Stratotype Section and Point (GSSP) in Newfoundland (Narbonne et al 1987;Kolesnikov et al 2015). The species P. delicatus and P. gracilis demonstrate a narrower stratigraphic range (Fig.…”