GEOLOGICAL AGE OF CHOUNIUKOU FORMATION

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.