Joints developed in rock mass have been considered as the living evidence of surface rocks being reshaped and reformed by multi-stages of tectonic evolution and stress fields. And they have been frequently used as indicators of the principle stress orientations in the reconstruction of stress fields and evolution(transition) processes. The paleo-reservoir of hydrocarbon in the Majiang area, Guizhou Province, is one of the largest paleo-reservoirs developed in residual units of marine strata in southern China. The area was shaped by multiple stages of tectonic movements and therefore experienced complicated tectonic evolution processes. As a result, numerous joints were developed in the strata of the area and offer a great opportunity for a profound study of the relationship between jointing characteristics and tectonic stress fields. Field measurements of joint sets were therefore performed to provide data for a statistical analysis on characteristics, occurrence, and geometries of the joints in the area. Based on a combination of the regional geological setting with an observation of joint intersection patterns and cutting relations between joints and faults, we suggest that there are five groups (stages) of joints developed in the area. They are, according to the age sequence of the strata (from old to young), the early conjugate shear joints of X intersections with NEE-SE orientation, the early conjugate shear joints of X intersections with SEE-NEE orientation, the overthrusting longitudinal joints of NE orientation, the open joints of SSE orientation and the shear joints of nearly EW orientation. They are the products of the Duyun Movement, early Guangxi Movement, Indo-China Movement, and Yanshang Movement respectively. The tectonic stress field of each stage is reconstructed through inversion based on data of joint occurrence. The calculation shows that the principle stresses of the stress fields in the Majiang area had shifted clockwisely from SEE to SE, SSE, and finally EW.
The erosion–deposition process and associated control mechanisms of the Nanliu River subaqueous delta, Southern China coast
