Interference fold patterns of the early Precambrian Rock Groups in the Songshan area, China

SummaryThe Songshan area is located in the southern part of the North China platform, which is one of the most completely cratonized tectonic units of China. Its basement has experienced a complex evolutionary history and was eventually consolidated at the end of early Proterozoic time about 1.7 Ga ago.A systematic study has been made of the deformation history of the lower Proterozoic Songshan Group and the Archean Dengfeng Group. At least two widespread episodes of deformation can be recognised in the early Proterozoic Zhongyue tectonic cycle and three in the Archean Songyang cycle. Large scale and small scale interference patterns of the superimposed folding are investigated with the aim of recognizing possible regularities in their occurrence and of gaining an insight into the regional deformation history. Two important aspects of superimposition relationships are illustrated: the control of earlier structures upon later ones and the reform of the former by thelatter; their geometrical regularities are also dealt with respectively.