Early-Middle Triassic boundary interval: Integrated chemo-bio-magneto-stratigraphy of potential GSSPs for the base of the Anisian Stage in South China

•Wantou (S. China) is ideal candidate for Early-Middle Triassic boundary stratotype.•Integrated magnetostratigraphy, U–Pb dating, ammonoids, conodonts, stable isotopes.•Preferred level is first Chiosella timorensis conodont near brief polarity chron MT1n.•High-resolution magnetic polarity and δ13C correlations to Europe/China sections.•Cooling of 4°C as δ13C rose 4‰ across boundary interval suggests CO2 drawdown.