The evolutionary sequence of the Tianlongshan Cave Temple, as shown by the archaeological typological study of the grotto shapes and the representation contents, characteristic features and carving techniques, can be divided into four periods, the absolute dates of which may be inferred as follows from the comparason with the images of other cave temples and from the related textual records.Period Ⅰ From the beginning of the Taichang Reign, Northern Wei Dynasty to the 4th year of the Wuding Reign, Eastern Wei Dynasty (532—546 AD). It is represented mainly by Grottoes 2 and 3 and characterized by the direct inheritance of distinctive features of the Longmen and Northern Wei Gongxian grottoes.Period Ⅱ From the 2nd year of the Tianbao Reign to the 2nd year of the Huangjian Reign, Northern Qi Dynasty(551—561 AD). It comprises Grottoes 1,10 and 16. Apart from the characteristics inherited from Period Ⅰ, there is distinct influence from the grottoes near Yecheng City.Period Ⅲ The 4th year of the Kaihuang Reign, Sui Dynasty (584 AD). It is represented only by Grotto 8 and characterized by the inheritance of traits from the second period.Period Ⅳ It is subdivided into an earlier stage and a later one. The former lasted from the 4th year of the Xianheng Reign to the 2nd year of the Yonglong Reign, Tang Dynasty (673—681 AD), and the latter from the 2nd year of the Yonglong Reign to the 4th year of the Chang’an Reign (681—704 AD). This period saw much influence from the Longmen Grottoes of the Tang Dynasty.
