Gl. Shen et al., GEOLOGICAL AGE OF CHOUNIUKOU FORMATION, Science in China. Series B, Chemistry, life sciences & earth sciences, 38(1), 1995, pp. 107-115
Studies demonstrate that the Chouriukou Formation of the Qilian Mounta
ins represents a lithostratigraphical unit across series, with its low
er part belonging to the Middle-Late Visean, middle pat to E-zone of t
he Early Namurian, and upper part to the Middle-Late Namurian. The Mid
-Carboniferous boundary passes through the bedding plane between the m
iddle and upper parts of this formation.