The Lomagundi-Jatuli Event and Earth’s oxygenation

Abstract

The Palaeoproterozoic Lomagundi-Jatuli Event (LJE) is the largest positive carbonate C-isotope ( δ13Ccarb) excursion in Earth history. Conventional thinking is that it represents a perturbation of the global C cycle between c. 2.3–2.1 Ga linked directly to the postulated Great Oxidation Event. Here we show that the LJE worldwide is, in fact, entirely facies (i.e. palaeoenvironment) dependent. During the LJE, the C-isotope composition of open and deeper marine settings remained undisturbed, with a mean d13Ccarb value of 1.5‰, whereas nearshore marine and coastal-evaporitic settings have means of 6.2‰ and 8.1‰, respectively. This finding refutes conventional thinking and obliges complete re-evaluation of concepts using the LJE as a means of assessing oxygenation of the atmosphere.

Calibrating the temporal and spatial dynamics of the Ediacaran - Cambrian radiation of animals

“…These include diurnal coupling between photosynthesis and carbonate saturation in shallow carbonate settings (Geyman and Maloof, 2019), local DIC pools of distinct isotopic composition (Cui et al, 2020b;Melim et al, 2002), and the possibility for water-column methanogenesis and carbonate recycling under low-sulfate conditions associated with restriction (Cui et al, 2020b). Additionally, facies-specific diagenetic regimes can yield distinct δ 13 Ccarb for time-equivalent sections in modern marine basins (Melim et al, 2002), and this has also been established in the Cryogenian interglacial ocean (Hoffman and Lamothe, 2019), and the Paleoproterozoic Lomagundi-Jatuli event (Prave et al, 2021). As a result, changes in δ 13 Ccarb may in fact archive contemporaneous pools of DIC from adjacent depositional settings with variable C isotope composition.…”