Phosphogenesis in the 2460 and 2728 million‐year‐old banded iron formations as evidence for biological cycling of phosphate in the early biosphere

Yi‐Liang Li,Si Sun,Lung S Chan

doi:10.1002/ece3.443

Abstract

The banded iron formation deposited during the first 2 billion years of Earth's history holds the key to understanding the interplay between the geosphere and the early biosphere at large geological timescales. The earliest ore-scale phosphorite depositions formed almost at ∼2.0–2.2 billion years ago bear evidence for the earliest bloom of aerobic life. The cycling of nutrient phosphorus and how it constrained primary productivity in the anaerobic world of Archean–Palaeoproterozoic eons are still open questions. The controversy centers about whether the precipitation of ultrafine ferric oxyhydroxide due to the microbial Fe(II) oxidation in oceans earlier than 1.9 billion years substantially sequestrated phosphate, and whether this process significantly limited the primary productivity of the early biosphere. In this study, we report apatite radial flowers of a few micrometers in the 2728 million-year-old Abitibi banded iron formation and the 2460 million-year-old Kuruman banded iron formation and their similarities to those in the 535 million-year-old Lower Cambrian phosphorite. The lithology of the 535 Million-year-old phosphorite as a biosignature bears abundant biomarkers that reveal the possible similar biogeochemical cycling of phosphorus in the Later Archean and Palaeoproterozoic oceans. These apatite radial flowers represent the primary precipitation of phosphate derived from the phytoplankton blooms in the euphotic zones of Neoarchean and Palaoeproterozoic oceans. The unbiased distributions of the apatite radial flowers within sub-millimeter bands do not support the idea of an Archean Crisis of Phosphate. This is the first report of the microbial mediated mineralization of phosphorus before the Great Oxidation Event when the whole biosphere was still dominated by anaerobic microorganisms.

Highlights

The Darwinian evolution of ecosystems at geological timescales is virtually coordinated by the evolving geological processes (Schwartzman et al 1993; Nisbet and Sleep 2001; Riding 2002)
We report the high similarity between the microbial phosphogenesis in the 535-million years ago (Myr) Lower Cambrian phosphorite and those in the 2460-Myr Kuruman and the 2728-Myr Abitibi banded iron formations (BIF)
Phosphogenesis in Banded Iron Formations (a) phenolic, d(C=CH), and m(C=CH) attached to cyclopentene ring vibrations (Fig.3), which together indicates the existence of scytonemin, the pigment only produced by oxygenic cyanobacteria to filter ultraviolet radiations (Edwards et al 1999)

Summary

Introduction

The Darwinian evolution of ecosystems at geological timescales is virtually coordinated by the evolving geological processes (Schwartzman et al 1993; Nisbet and Sleep 2001; Riding 2002). The feedback mechanisms between geoenvironment, ecosystem and climate that regulate the evolution of the whole Earth system can be traced by the sedimentary geology of phosphate through the deep time (Fo€llmi 1996; Fo€llmi et al 2004). The geochemical cycle of phosphorus is a critical factor that governs the primary productivity of the aquatic ecosystems since the beginning of biological evolution (Geider et al 2001; Bekker et al 2010). For the first 2 billion years of Earth with life, banded iron formations (BIF) are the most important sedimentary rocks (Ohmoto et al 2006; Bekker et al 2010) holding key evidence for biological cycling of phosphorus and bioproductivity (Cloud 1973; Bjerrum and Canfield 2002; Kappler et al 2005).

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Discussion

Conclusion