Rare earth elements in the terminal Ediacaran Bambuí Group carbonate rocks (Brazil): evidence for high seawater alkalinity during rise of early animals

Carbon and sulfur biogeochemical cycles in the Brazilian Ediacaran record

“…The late HST carbonate successions are associated with a remarkable basin-scale increase in the Sr/Ca on the carbonate deposits probably driven by enhanced alkalinity and/or more aragonitc conditions (Caetano-Filho et al, 2019;Paula-Santos et al, 2020). The whole HST…”

“…It was interpreted as a significant paleoenvironmental change recorded throughout the basin, with possibly enhanced alkalinity, more aragonitic conditions and/or even hypersalinity, which persist to the overlying sequence (Figs. 4.2, 4.3, and 4.4; Table S1 -Supplementary Materials; Appendix B; Caetano- Filho et al, 2019;Paula-Santos et al, 2020).…”

“…5.6). These high Sr mass fractions and Sr/Ca ratios are frequent geochemical signatures in late Ediacaran carbonate successions, probably deposited in times of more alkaline seas (e.g Caetano-Filho et al, 2019;Paula-Santos et al, 2020)…”

“…The Middle Bambuí Excursion would represent a transition for a methanogenic dominated basin after sulfate exhaustion and limited sulfate-reduction due to orogenic build-up and marine disconnection. A shallow chemocline would decrease methane oxidation in the Bambuí sea and favors methane escape to the atmosphere (based on data fromPaula-Santos et al, 2020).…”

“…documented in several Ediacaran successions, especially high Sr/Ca ratios, interpreted as a time of enhanced alkalinity which may have favored the development of carbonate biomineralization by these early skeletal metazoans, remarkably represented by Cloudina genus (e.g Wood et al, 2018;Caetano-Filho et al, 2019;Paula-Santos et al, 2020…”