Large igneous provinces track fluctuations in subaerial exposure of continents across the Archean–Proterozoic transition

Abstract

et al., 2001) indicate that Archean continents (e.g. the Pilbara and Kaapvaal cratons) were at least locally raised above sea level. In the Sighbhum craton, continental emergence above sea level may have begun as early as 3.3.-3.2 Ga (Chowdhury et al., 2021). However, on a global scale, Precambrian sedimentation patterns indicate deposition in predominantly oceanic settings or epeiric seas, and generally low-freeboard conditions (freeboard refers to the average elevation of continents above sea level) until the Neoarchean to early Proterozoic (Campbell & Davies, 2017; Eriksson et al., 2005; Eriksson & Condie, 2014). Limited exposure of Archean continents is supported by geochemical proxies and numerical models (Flament

Low δ18O and δ30Si TTG at ca. 2.3 Ga Hints at an Intraplate Rifting Onset of the Paleoproterozoic Supercontinent Cycle

“…Besides, the appearance of the ca. 2.3 Ga low-δ 18 O magmatic activities coincided with the newly identified widespread 2.4-2.2 Ga subaerial volcanism (Liebmann et al, 2022). In particular, in Earth's surface environments, the near-synchronous increase in the δ 18 O of sedimentary rocks and their recycling products of the ca.…”

“…In particular, in Earth's surface environments, the near-synchronous increase in the δ 18 O of sedimentary rocks and their recycling products of the ca. 2.4-2.2 Ga strongly peraluminous granites were reported (Liebmann et al, 2021(Liebmann et al, , 2022Xie et al, 2022). Given the near-synchronous changes of O isotopic compositions at both granitic end-members (A-and S-type), as well as the rapid increase in average detrital zircon δ 18 O values from <7.5‰ before GOE to 9-11‰ by ca.…”

Deconstructing the Lomagundi-Jatuli Carbon Isotope Excursion

“…Similarly, it has been proposed that large igneous provinces record a shift to increased subaerial exposure of continents from ca. 2.4 to 2.2 Ga (Liebmann et al 2022).…”

“…If authigenic carbonate mineral formation was widespread during the LJE, it would result in the sequestration of large amounts of 12 C in sedimentary carbonate minerals and therefore an increase in residual marine δ 13 C DIC (Higgins et al 2009, Schrag et al 2013. Variations in the formation and burial rates of these strongly 12 C-enriched authigenic carbonate minerals have been invoked to explain important aspects of the δ 13 C record, such as the persistence of baseline marine δ 13 C values near 0‰ through most of Earth history (Laakso & Schrag 2022), despite oxygen production rates that must have varied significantly. In this framework, the LJE would be explained, at least in part, by increased burial of authigenic carbonate minerals.…”

“…Although this model may be able to explain the LJE without invoking order-of-magnitude changes in burial fluxes of organic carbon (Laakso & Schrag 2022), it has not achieved widespread acceptance, primarily because direct evidence of enhanced authigenic carbonate mineral formation in the geological record is sparse, let alone during the LJE. The initial hypothesis of Higgins et al (2009) implied that authigenic carbonate formation would be minimal in oxygenated oceans; this has been corroborated through modern sedimentary pore fluid database analyses (Bradbury & Turchyn 2019), although authigenic carbonate mineral formation can be locally significant, such as on the Amazon shelf, where it is estimated to constitute ∼30% of total carbon burial locally (Aller et al 1996).…”