Its first setup was soon after the fourth year of Yuanshou in Wudi period(B. C. 119), and the places were scattered in the belt from Shuofang to Lingju.
其始置时间为汉武帝元狩四年（前119）后不久，最早设置的地点在朔方至令居一带；
3
The mid-belt form flowage fold, from the mid-belt to margin belt, the structural types are successively sheath fold; A-fold; B-fold.