Early Prosperity of Iron Bacteria at the End of the Paleoproterozoic Era. Issue 9 (30th April 2022)

• Record Type: Journal Article
• Authors: Qiu, Yifan; Qin, Liping; Huang, Fang; Zhao, Taiping; Li, Yiliang
• Is Part Of: Geophysical research letters. Volume 49:Issue 9(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-30
• Subjects: late Paleoproterozoic era -- microaerophilic iron‐oxidizing bacteria -- subaerial iron deposition -- an age of iron bacteria; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL097877
• Languages: English
• ISSNs: 0094-8276

Abstract

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 δ 56 Fe with positive δ 53 Cr 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. Plain Language Summary: A new type of iron formation (IF) with hematite (Fe2 O3 ) as the predominant iron oxide was deposited at the end of the Paleoproterozoic era. Based on the combined studies of petrography, mineralogy, elemental geochemistry, and Fe‐Cr isotopic compositions of the Yunmengshan IF, we propose that it was the microaerophilic iron‐oxidizing bacteria that oxidized the terrestrial Fe(II) to Fe(III). With the gradual oxidation of Earth's surface at the transition between the Paleo‐ and Mesoproterozoic eras, the global atmospheric O2 reached a favored concentration that facilitated the prosperity of the microaerophilic iron‐oxidizing bacteria. An enhanced oxidative weathering transiently happened on land, and the seeping of Fe(II)‐fluids in the coastal environments produced the energy source for the chemolithotrophic iron‐oxidizing bacteria. These favorable conditions facilitated the leading role of Fe(II)‐oxidizing bacteria in Fe‐oxidation in the terrestrial environments at the end of the Paleoproterozoic era. Key Points: Geochemical and paleoenvironmental data suggest that the Yunmengshan iron formation (IF) was deposited in a subaerial environment The modern iron bacterial mats show similar elemental and isotopic features to the Yunmengshan IF Iron bacteria began to flourish in terrestrial environments at the end of the Paleoproterozoic era