Early Prosperity of Iron Bacteria at the End of the Paleoproterozoic Era

Abstract

Various iron formation (IFs) document the interplay between the geosphere and the early biosphere during their co‐evolution. At the transition between the Paleo‐ and Mesoproterozoic eras, the oxidation of the atmosphere and ocean resulted in the waning of the typical marine deposited banded IFs. Here, we report the ∼1.7 Ga Yunmengshan IF at the southern margin of the North China Craton deposited in the intertidal to upper subtidal zone belonging to river delta of coastal environments. The combined REE + Y patterns and negative δ56Fe with positive δ53Cr values reveal terrestrial precipitation of iron oxide and an enhanced continental oxidative weathering at the end of Paleoproterozoic era due to increased atmospheric oxygen level. The oxygen level happened to have facilitated the early prosperity of microaerophilic Fe(II)‐oxidation bacteria on Earth's terrestrial surface, which is recorded by the coastal shallow water iron deposits globally characterized by their small scale and subaerial features.

Marine Aluminum Phosphate–Sulfate Authigenesis as a Phosphorus Sink During Mid‐Proterozoic Oxygenation

“…In addition, Th shows positive correlations with ∑REE ( R 2 = 0.26; Figure S3d in Supporting Information ) and Ce SN /Ce SN * ( R 2 = 0.39; Figure S3e in Supporting Information ), implying that the Ce anomalies could be more prominent if there is no siliciclastic contamination. Hence, the YMS ironstones were deposited in oxic seawater conditions, consistent with results from the non‐fractionated Fe isotope and highly fractionated Cr isotope in the YMS ironstones of the adjacent Daimei section (Qiu et al., 2022).…”

“…Other authigenic aluminum phosphate‐sulfate minerals are also widely documented from several continents, such as Madagascar metaquartzite from Madagascar (Morteani et al., 2007), Warton sandstone from Australia (Rasmussen, 2000), Thelon sandstone from Canada (Gall et al., 2006). The widespread distribution of svanbergite across different continents can plausibly be attributed to a global increase in diagenetic phosphorus (P) sink at ∼1.7 Ga, corresponding to the observed oxygenation at this time (Qiu et al., 2022). While enhanced oxidative weathering of sulfide minerals during the oxygenation event can lead to more efficient P recycling in mid‐depth euxinic water (Alcott et al., 2022; Guilbaud et al., 2020), the oxygenation could also promote svanbergite authigenesis in coastal areas (Figure 3b).…”

“…This low sulfate concentration, compared with that of the modern ocean (∼29 mM; Millero, 2005), makes the formation of svanbergite in sediments challenging. The increased atmospheric oxygen around 1.7 Ga, as indicated by the highly fractionated Cr isotope in the YMS ironstones (Qiu et al., 2022), may have promoted oxidative continental weathering (Chu et al., 2023) and increased sulfate and Sr input to the oceans. The bulk‐rock Sr isotope values are similar to that of contemporary seawater, indicating that Sr is largely sourced from seawater (Chu et al., 2023).…”

“…Abundant svanbergite has been identified in the ∼1.7 Ga Yunmengshan (YMS) ironstone, a chemical sedimentary rock with Fe >15 wt% (Young, 1989), from the Xiong'er basin, North China, which offers a valuable opportunity to study the P cycling under relatively high atmospheric oxygen conditions in the terminal Paleoproterozoic ocean. The presence of highly fractionated chromium, but unfractionated iron isotopes (Qiu et al, 2022), and radiogenic seawater osmium (Chu et al, 2023) in the YMS ironstones suggest oxygenated conditions, at least transiently in shallow seawater at ∼1.7 Ga. In this study, we mainly focus on the YMS ironstones and uncover the contemporary P cycling under relatively high atmospheric oxygen levels, using mineralogical and geochemical analyses.…”

1.44 Ga Oxygenation Event: Evidence From the Southern Margin of North China

“…Multiple pulsed oxygenation events have been identified during the mid‐Proterozoic, including those at ∼1.7 Ga (Qiu et al., 2022), ∼1.57 Ga (e.g., Shang et al., 2019; Tang et al., 2022; Xu et al., 2023; Zhang et al., 2018), ∼1.4 Ga (Wei et al., 2021; Yu et al., 2022; Zhang et al., 2016), and ∼1.3–1.1 Ga (Canfield et al., 2018). Among them, the ∼1.44 Ga Tieling Formation provided robust records of shallow marine oxygenation, including a positive shift in I/(Ca + Mg), a significant negative Ce anomaly (Wei et al., 2021; Yu et al., 2022), and the development of water‐column carbonate mud in the Member II of this formation, suggesting a moderately oxygenated shallow seawater (cf.…”