Fig. 2: Profiles of Haojiagou (Upper, HJG) and Qilixia (Lower, QLX) sections.

(a, g) Organic carbon isotope (δ¹³C_org, ‰); (b, h) Mercury concentrations (Hg, ppb); (c, i) Ratios of mercury to total organic carbon (Hg/TOC, ppb/wt.%); (d, j) Mass independence fractionation of odd-Hg isotope (Δ¹⁹⁹Hg, ‰); (e, k) Chemical index of alteration (CIA) and (f, l) clay minerals. The eccentricity cycle and ages are from Sha et al.⁵³ and Li et al.⁷⁰ for Haojiagou and Qilixia respectively. The red crosses in represent δ¹³C_org data from Sha et al.⁵³. Open and purple filled circles in c and i represent samples with TOC < 0.2 wt.% and ≥ 0.2 wt.%, respectively. ICW Intense chemical weathering interval; TJT Triassic–Jurassic transition; ME mercury-enriched interval. The red and green bar at the base of column d and j represent the volcanic (V) and terrestrial (T) compositions of Δ¹⁹⁹Hg respectively. The arrow for the ICW represents the uncompleted records in the Early Jurassic for QLX. The horizon bars of the Δ¹⁹⁹Hg profiles represent standard deviation (2σ) values. Abbreviations: Sy System, St (sub)stage, F formation, B bed, Z sporomorph assemblage zone, Ec. eccentricity cycle, M member, Jur. Jurassic, Het. Hettangian, ZZC Zhenzhuchong, ICIE Initial carbon isotope excursion, MCIE Main carbon isotope excursion, PCIE precursor carbon isotope excursion. Note: full geochemical data are in Supplementary Figs. 2–3. Source data are provided as a Source Data file.