Fig. 2
Summary of inertinite abundance relative to the geological age, atmospheric paleo-oxygen concentration, paleotemperature, and carbon dioxide concentration fluctuations. a Geochronological distribution of global inertinite abundance (Diessel 2010). Dashed lines refer to the three repetitions of inertinite abundance from high to low; mf: Mineral-free; b Geochronological distribution of inertinite abundance in China. Four major cycles are identified (marked by red lines); c Curve of atmospheric paleo-oxygen concentration in previous studies (Berner 1999, 2006; Berner and Kothavala 2001; Ward et al. 2006); d Simulation curve of atmospheric paleo-oxygen concentration in this study. Dashed lines in c and d refer to the pO2 value of the modern atmosphere (approximately 21%); e Variations of the carbonate-hosted oxygen isotopes, and the calculated temperatures (Shaviv and Veizer 2003). Dashed line refers to the base line of oxygen isotope; f Changes in atmospheric carbon dioxide concentration. R: Ratio of atmospheric CO2 concentration in geological history compared to the modern atmospheric CO2 concentration) (Royer et al. 2004)