Supporting information for "1.38 Ga four-layer tuff marker horizon in North China black shales as a chronostratigraphic boundary for the pre-Ediacaran geological time scale"

This supporting information includes detailed descriptions of field occurrences and samples, analytical methods for U–Pb CA–ID–TIMS geochronology (Text S1), field photographs showing the four-layer tuff marker horizon within black shales of the Xiamaling Formation in the Yanliao Basin, North China Craton (Figures S1 and S2), cross sections showing sample locations of tuffaceous ash beds within black shales of the Xiamaling Formation at Zhaojiashan and Beilu sections (Figure S3), summary of the previously and newly obtained zircon U-Pb isotopic data for volcanic tuff units from the Xiamaling Formation, North China Craton (Tables S1), and U-Pb CA-ID-TIMS isotopic data for volcanic tuff units from the Xiamaling Formation, North China Craton (Tables S2).