Organic matter sulfurization and organic carbon burial in the Mesoproterozoic

Throughout the Proterozoic Era, sedimentary organic carbon burial helped set pace of global oxygenation and acted as a major modulator atmospheric CO2 climate. Although rocks generally contain low concentrations matter (OM), there are key exceptions to this rule, including relatively OM-rich Arctic Bay shales from Baffin Island, Canada (Bylot Supergroup, Borden Basin, ∼1.05 Ga). The mechanisms driving elevated OM in these other remain poorly understood. In Mesozoic Cenozoic, sulfurization can be driver enhanced across range redox conditions comparable those inferred for many environments. Therefore, study, we evaluate role preservation Mesoproterozoic Basin discuss its relevance systems general. We present first evidence syngenetic-to-early-diagenetic basin, which begins fill several-billion-year gap our record S Earth history. find that was particularly extensive shallow-water section (Alpha River) but less deposited deeper water (Shale Valley), is consistent with models infer sulfidic ‘wedges’ or O2-minimum-zone-type structures on shelf margins at least intermittently time. At shallower site, pyrite similarly 34S-depleted thus likely formed roughly same time near sediment–water interface under previously interpreted have been ferruginous sulfidic. contrast, deeper-water large S-isotope differences between along apparent intensities indicate formation favored over during early sedimentation variable primarily conditions. biomass substantially sulfurized, indicators intensity not correlated concentrations, therefore does appear primary Formation shales. link total may modulated deposition by iron availability, nutrient cycling, particle dynamics Mesoproterozoic.