7.7 The Earliest Phosphorites: Radical Change in the Phosphorus Cycle During the Palaeoproterozoic

Fossil evidence of iron-oxidizing chemolithotrophy linked to phosphogenesis in the wake of the Great Oxidation Event

“…The phosphorites of Rajasthan, along with similar phosphatic stromatolites of central India, record some of the oldest sedimentary phosphorite deposits (Cook et al, 1990;Papineau, 2010;Lepland et al, 2013). The process(es) involved in localizing apatite within stromatolites, an enigmatic feature of Paleoproterozoic phosphorites from western and central India, are not well understood (McKenzie et al, 2013).…”

Multiple sulphur isotope records tracking basinal and global processes in the 1.98 Ga Zaonega Formation, NW Russia

“…It is postulated that these carbon cycle perturbations were driven by intensified subaerial oxidative weathering, with concomitant increases in riverine-derived nutrients, intensifying biological activity and facilitating the growth of the marine sulphate reservoir (Bekker et al, 2006;Schröder et al, 2008;Reuschel et al, 2012). Such inferences are supported by the presence of the oldest known globally significant phosphorites associated with the Shunga Event (Bekker et al, 2003;Lepland et al, 2013Lepland et al, , 2014 and the oldest extensive evaporites of the ca. 2.0 Ga Tulomozero Formation, which also archive the Lomagundi-Jatuli excursion in the Onega Basin of NW Russia (Morozov et al, 2010;Krupenik et al, 2011;Blättler et al, 2018).…”

Identifying global vs. basinal controls on Paleoproterozoic organic carbon and sulfur isotope records

“…The Neoarchean and Paleoproterozoic eras saw drastic perturbations in Earth system processes, spanning from the geodynamic, the emergence of continents and the initiation of supercontinent cycles (Reddy and Evans, 2009), to the climatic, as recorded by several episodes of global glaciations (Kopp et al, 2005;Young et al, 1998). In concert with those were major changes in Earth's surface environments: widespread accumulation of iron formations (Bekker et al, 2014;Cloud, 1973;Holland, 1978;Klein, 2005;Konhauser et al, 2002Konhauser et al, , 2017, disappearance of detrital pyrite and uraninite grains (Berkner and Marshall, 1965;Cloud, 1968;Holland, 2006), loss of mass-independent sulfur isotope fractionation (Farquhar et al, 2000;Guo et al, 2009;Luo et al, 2016), the large-magnitude positive δ 13 Ccarb excursion of the Lomagundi-Jatuli Event (LJE; Baker and Fallick, 1989;Karhu and Holland, 1996), accumulation of exceptionally organic-rich sediments of the Shunga Event (Melezhik et al, 1999;Kump, 2011;Strauss et al, 2013), and the appearance of phosphorous-rich sedimentary deposits (Lepland et al, 2013;Papineau, 2010). These changes are thought to have occurred as a consequence of the build-up of atmospheric oxygen to above 0.001% present atmospheric levels at c. 2.4-2.3 Ga (Fig.…”