Extended Data Fig. 7: NEOCARBSULF-∆′17O model results from 1,000 to 500 Ma.
From: Two-billion-year transitional oxygenation of the Earth’s surface
a, Model input of δ13Ccarb record. Black circles denote data from this study; the dark-grey dashed line shows the moving average, and the light grey band indicates ±1 s.d. b, Model output of \({p}_{{{\rm{O}}}_{2}}/{p}_{{{\rm{CO}}}_{2}}\) ratios. The black line represents the mean result of 1,000 model runs, with the grey shaded band denoting ±1 s.d. c, Model input of gross productivity. Scenario 1 (solid line) assumes constant productivity; Scenario 2 (dashed line) represents time-dependent estimates based on sedimentary phosphorus concentrations (see Extended Data Fig. 6). d, Modelled O2 residence time, calculated as the ratio of \({p}_{{{\rm{O}}}_{2}}\) to productivity. Dark-blue and light-blue lines denote the respective mean values under Scenario 1 and Scenario 2 assumptions, respectively. e, Modelled ∆′17\({{\rm{O}}}_{{{\rm{O}}}_{2}}\) values. Light and dark-blue lines represent the mean values for the two scenarios, with shaded envelopes indicating ±1 s.d. The model shows that during all major negative δ13Ccarb excursions, \({p}_{{{\rm{O}}}_{2}}/{p}_{{{\rm{CO}}}_{2}}\) ratios dropped by roughly an order of magnitude, mostly from about 10 to about 1, accompanied by parallel decreases in O2 residence time. Except for the SE, other δ13Ccarb excursions, specifically the Majiatun, BSA, Trezona, CANCE, and BACE, exhibited increased ∆′17\({{\rm{O}}}_{{{\rm{O}}}_{2}}\) values.
