Fig. 2
From: Enhanced flux of extraterrestrial 3He across the Permian–Triassic boundary
Stratigraphic He and Ir profiles. Stratigraphic profiles of a 3He concentrations, b 3He/4He ratios, c 3He/4He ratios of acid-insoluble residues produced during stepwise heating at temperatures of 750–950 °C, and d excess Ir in bedded cherts of the Waidani section. Red and yellow symbols in the 3He profile represent the extraterrestrial fraction and measured 3He concentrations, respectively. The base of the Triassic and MEE horizons in this section are defined by the occurrence of the conodont Hindeodus parvus and disappearance of Permian radiolarian fossils, respectively