Oxygenation of the Earth aided by mineral–organic carbon preservation

Abstract

Photosynthesis produces molecular oxygen, but it is the burial of organic carbon in sediments that has allowed this O2 to accumulate in Earth’s atmosphere. Yet many direct controls on the preservation and burial of organic carbon have not been explored in detail. For modern Earth, it is known that reactive iron phases are important for organic carbon preservation, suggesting that the availability of particulate iron could be an important factor for the oxygenation of the oceans and atmosphere over Earth history. Here we develop a theoretical model to investigate the effect of mineral–organic preservation on the oxygenation of the Earth, supported by a proxy compilation for terrigenous inputs and the burial of reactive iron phases, and find that changes to the rate of iron input to the global ocean constitute an independent control on atmosphere–ocean O2 and marine sulfate levels. We therefore suggest that increasing continental exposure and denudation may have helped fuel the rise in atmospheric O2 and other oxidants over Earth history. Finally, we show that inclusion of mineral–organic preservation makes the global marine O2 reservoir more resilient to changes in nutrient levels by breaking the link between productivity and organic carbon burial. We conclude that mineral–organic preservation is an important missing process in current assessments of Earth’s long-term carbon cycle.

Evolution of iron and oxygen biogeochemical cycles during the Precambrian

“…state with elevated Fe availability (Guilbaud et al, 2020). Therefore, better understanding of the interaction between the Fe, O 2 , and P cycles might offer unique insights into the dynamics and evolution of Earth's oxygenation history (Halevy et al, 2017;Laakso & Schrag, 2014;Ozaki, Thompson, et al, 2019;Watanabe et al, 2023;Zhao et al, 2023). However, a cause-and-effect rela- S1).…”

Vertical distribution of Fe, P and correlation with organic carbon in coastal sediments of Yellow Sea, Eastern China

“…Most studies have discussed the mechanism for stabilizing TOC by iron minerals in continent soil and in the lakes, salt marsh wetlands, or ocean sediments (Lalonde et al, 2012;Ma et al, 2018;Reichenbach et al, 2023;Zhao et al, 2023). The TOC sequestration controlled by iron minerals is complicated and strongly related to the redox conditions of sediments (Hartnett et al, 1998;Hemingway et al, 2019).…”

“…The TOC sequestration controlled by iron minerals is complicated and strongly related to the redox conditions of sediments (Hartnett et al, 1998;Hemingway et al, 2019). While study pointed that mineralorganic preservation is an important missing process in current assessments of Earth's long-term carbon cycle (Zhao et al, 2023). Redox conditions of coastal sediments vary greatly in vertical profiles as terrigenous input (Anschutz et al, 2019), and Fecarbonates are enriched commonly due to dynamic drive of the tide (Lapointe et al, 1992).…”

“…In sediments, the interaction between minerals and organic matter occurs preferentially on specific minerals; therefore, the mineral composition is a crucial factor for the sequestration of organic matter (Hedges and Keil, 1995;Kleber et al, 2021). Many studies have proven that Fe minerals are important carriers of organic carbon in terrestrial soil (Sarkar et al, 2018;Kleber et al, 2021), and in the ocean sediment (Zhao et al, 2023). Fine-grained components in coastal sediments positively correlated with the contents of unstable minerals (Cao et al, 2018), especially the contents of Ca/Mg-rich carbonates with poor stability (Fookes and Higginbottom, 1975;Yalcin et al, 2022).…”

“…Recently, scientists have proposed that the current hypothesis that the mineral matrix has a protective mechanism for TOC is simplistic, and the spatial and functional complexity of the mineral-organic matter should be considered (Yalcin et al, 2022). And study pointed that mineral-organic preservation is an important missing process in current assessments of Earth's longterm carbon cycle (Zhao et al, 2023). Hence, analyzing the correlation between the occurrence of organic carbon in the sedimentary profile of coastal zone and the occurrence of iron and manganese minerals is crucial to determine their contribution to the "carbon sink" of "blue carbon".…”