Fig. 1

Spatial distribution of the data points of inertinite abundance in coal deposits during different coal-forming periods in China. The map of China is modified after the Standard Map Service of the National Administration of Surveying, Mapping and Geoinformation of China (http://bzdt.ch.mnr.gov.cn/) (No. GS(2016)1569). E.: Early; M.: Middle; L.: Late; and the same follows