Inner Mongolian Axis
This axis is an elongated uplifted tectonic structure along the northern margin of the North China Platform. The name was coined by Huang Jiqing in 1945. It runs east from Alashan in the west via Daqingshan Mountain in Inner Mongolia to Yanshan Mountain in Hebei. Its total length is approximately 2,000 km, and it is approximately 300 km wide. Precambrian crystalline basement outcrops are extensive in the region, which are overlain by Mesozoic and Cenozoic basin sediments. There is a lack of Palaeozoic sedimentary cover. For a long time, this structure was considered a palaeo-uplift separating the North China Platform from the Xingmeng Sea Trough to the north during the Palaeozoic Era. However, later research suggested that it might have formed due to Mesozoic thrusting and subsequent exposure of the Cambrian System and that it was not an uplifted area in the Palaeozoic.