This axis originally referred to the area with exposed Precambrian metamorphic rocks extending north-south from Kangding, Sichuan Province, to Honghe, Yunnan Province. The name was coined by Huang Jinqing in 1945. It was thought to be a continuously uplifted region since the Phanerozoic Eon. Tectonically, it was grouped as a secondary positive tectonic unit on the western border of the Yangtze Platform. However, recent studies suggest that the metamorphic rocks in this area are Mesoproterozoic and Neoproterozoic in age. Strong rifting with intense volcanic activity occurred in the late Neoproterozoic; hence, this term is now seldom used.