Constraints on Paleoproterozoic atmospheric oxygen levels

Abstract

The oxygenation of Earth's surface environment dramatically altered key biological and geochemical cycles and ultimately ushered in the rise of an ecologically diverse biosphere. However, atmospheric oxygen partial pressures (O) estimates for large swaths of the Precambrian remain intensely debated. Here we evaluate and explore the use of carbonate cerium (Ce) anomalies (Ce/Ce*) as a quantitative atmospheric O proxy and provide estimates of Proterozoic O using marine carbonates from a unique Precambrian carbonate succession-the Paleoproterozoic Pethei Group. In contrast to most previous work, we measure Ce/Ce* on marine carbonate precipitates that formed in situ across a depth gradient, building on previous detailed sedimentology and stratigraphy to constrain the paleo-depth of each sample. Measuring Ce/Ce* across a full platform to basin depth gradient, we found only minor depleted Ce anomalies restricted to the platform and upper slope facies. We combine these results with a Ce oxidation model to provide a quantitative constraint on atmospheric O 1.87 billion years ago (Ga). Our results suggest Paleoproterozoic atmospheric oxygen concentrations were low, near 0.1% of the present atmospheric level. This work provides another crucial line of empirical evidence that atmospheric oxygen levels returned to low concentrations following the Lomagundi Event, and remained low enough for large portions of the Proterozoic to have impacted the ecology of the earliest complex organisms.

On the co‐evolution of surface oxygen levels and animals

“…1.9 and ca. 1.45 Ga benthic carbonates suggests a p O 2 of 0.1%–1% PAL (Bellefroid et al, ; Bellefroid, Planavsky, Hood, Halverson, & Spokas, ). Finally, recent work on rare oxygen isotopes (∆ 17 O) recorded in ca.…”

“…For instance, the intermediate‐complexity Earth system model cGENIE has been utilized by several groups to explore marine redox structure leading up to and during the rise and diversification of metazoans (Reinhard et al, ), and more recently to explore the potential impacts of marine nutrient levels on eukaryotic trophic ecology (Reinhard et al, accepted). As an alternative approach, estimates of marine physical dynamics at various climate states from higher resolution GCMs have been coupled with marine biogeochemical models (Bellefroid et al, ). This method allows for stochastic approaches to quantify unavoidable uncertainties when modeling Proterozoic environments.…”

A paleosol record of the evolution of Cr redox cycling and evidence for an increase in atmospheric oxygen during the Neoproterozoic

“…A vague picture of the temporally and/or spatially confined nature of these pulses may be drawn from a cluster of ca. 1.9–1.8 Ga paleosols and marine sediments from Canada, which show quite different ranges of δ 53 Cr (Figure ), as well as variable Fe mobility (Babechuk et al, ; Bellefroid et al, ; Frei & Polat, ; Toma, Holmden, Shakotko, Pan, & Ootes, ). The redox conditions that prevailed in any one of these paleosols appear to have been localized in time and/or space, as the majority of Proterozoic paleosols as well as marine records indicate that the background state was one of limited (<1% PAL) atmospheric oxygen.…”

“…The last decade of research has led to a more nuanced view of atmospheric pO 2 , which recognizes that pO 2 may have risen to Phanerozoic-like levels in the Paleoproterozoic (Canfield, 2005;Lyons et al, 2014;Partin et al, 2013) and crashed to levels much lower than traditionally envisioned in the mid-Proterozoic (e.g., Bellefroid et al, 2018;Canfield, 1998;Cole et al, 2016;Crockford et al, 2018;Gilleaudeau et al, 2016;Hardisty et al, 2017;Li et al, 2015;Lyons et al, 2014;Planavsky et al, 2014;Scott et al, 2011;Tang, Shi, Wang, & Jiang, 2016). Evidence for inhibited Cr oxidation in the mid-Proterozoic (Cole, O'Connell, & Planavsky, 2018;Cole et al, 2016;Planavsky et al, 2014) also supports the case for low surface oxygen levels.…”

Shallow water anoxia in the Mesoproterozoic ocean: Evidence from the Bashkir Meganticlinorium, Southern Urals

“…Neoproterozoic. Estimates for Mesoproterozoic atmospheric oxygen partial pressure ( O2) 627 suggest a decline to levels between ~0.01 to 0.1 PAL following the Lomagundi Event, with 628 persistent low values until the Late Neoproterozoic (Daines et al, 2017;Bellefroid et al, 2018;629 Crockford et al, 2018). Since there was limited, if any, variation in the terrestrial flux of sulfate 630 to the oceans in the aftermath of the GOE, the primary control on seawater sulfate 631 concentration must have been the expansive drawdown of sulfate (as pyrite) into sulfidic 632 environments in the water column and pore waters .…”