The upper Ordovician Wufeng Formation and the first member of the lower Silurian Longmaxi Formation are well exposed in Bayu outcrop Daozhen

northern Guizhou

with clear and complete stratigraphic boundaries. Under the control of global sea level changes

the Wufeng Formation and the first member of the Longmaxi Formation develop clay-bearing siliceous shale

siliceous shale

clay-bearing siliceous shale

argillaceous shale and silty shale from bottom to top

which display similar longitudinal superimposition characteristics to the Pengshui area on the edge of the Sichuan Basin and Jiaoshiba area in the basin. Lithology of the organic-rich shale in Wufeng Formation and the first member of the Longmaxi Formation in Bayu outcr

op of Daozhen is dominated by clay-bearing siliceous shale and siliceous shale

which have the same organic matter enrichment features as that in the Pengshui and Jiaoshiba area. Specifically

TOC

is positively correlated with the content of quartz

and negatively correlated with the content of clay minerals. The total thickness of organic-rich shale in the Wufeng Formation and the first member of the Longmaxi Formation at this profile is 26.1 m

which is lower than that in the Pengshui and the Jiaoshiba area

reflecting a relatively shallow-water depositional environment in the Daozhen area.