The Mesozoic volcanic rocks in Nanjing-Wuhu Basin originated from the mantle source.Maoshan and Chaoxian-Hanshan fold zones on both east and west sides of the basin are symmetrically distributed

with an overturned facies strike overthrusting to the Mesozoic-Cenozoic stratum.The intensely pressed

and the overturned facies strike

of Qinglong limestones from the middle-lower Triassic can be found on both flanks of median synclinorium in the west sectionof Ningzhen fold system.Continental clastics from the upper Triassic-lowermiddle Jurassic can be seen only in their core.Things for Nanjing-Wuhu Basin from the east foot of Chaoxian-Hanshan mountain system to the west foot of Maoshan mountain arc all just the same.It is believed that

according to the geological facts showing in the deep texture

fold systems on the east and west flanks of Nanjing-Wuhu Basin and southwestern end of Ningzhen fold on the north of the basins were previously connected with each other.It is because the subduction of the Pacific plate towards the Eurasian plate that brought about the upwarping of the mantle within the area

the extending

the thinning out and cracking of the crust

the exploiding of magama

the drifting of the basement and overlying sedimentary mantle to both east and west and then hiding

and the intensely folding and overturning of overlying formations on both sides

even overthrusting above a new formation within the basin and the volcanic system

thus forming the nappe structure of facies strike on the east and west flanks of the basin at last.This is the basin marginal ramp model formed by volcanic activity of rift type.