Typical superimposed fold structure occurs in the Zhengba region

southern Shaanxi Province

where the Micangshan and Dabashan structures intersect with each other.The nearly EW-NEE trending fold structures in Micangshan area and the nearly SN-NNE trending closed fold structures in Dabashan area are in traverse superimposition.The superimposed folds developed in the Sishang area show that the early E-W trending folds were superimposed and deformed by the late S-N trending folds

resulting in the nearly S-N occurrence of the regional strata.These folds were developed during J

3

-K

1

.However

the folding and deformation of the Micangshan area happened in the Late Jurassic(J

3

)

a little earlier than that of the Zhenba area(the west segment of the sou-thern Dabashan Mountain)

which happened during the Late Jurassic and Early Cretaceous(J

3

/K

1

).The intersection and deformation of Dabashan and Micangshan were resulted from superimposition of different tectonic systems during the Yanshanian intracontinental orogeny on the basis of the Indosinian collision orogeny.