Fracture systems and dissolution cavities in Wadi As Sir Formation, Thughrat Asfour area, Jordan

The fracture systems and their relationship with dissolution cavities and/ or karst development in the Turonian Limestone of Wadi As-Sir Formation were studied along abandoned quarries and road cuts in a folded area on the Irbid- Jerash Highway. A total of 740 fracture planes were measured in the field. Among them, sixty striated planes were analyzed for fault-strain by means of the TENSOR structural software. The other fracture data are represented as a rose diagram showing the orientation of the fractures. Four sets of fractures are distinguished in the study area these are: a) Extension fractures (having orientation NNW-SSE (N20°W to N40°W)); b) Release fractures (having orientation ENE- WSW and WNW-ESE (N70°E to S80°E)); c) Shear fractures set-1 (having orientation N- S (N10°W to N10°E)); and d) Shear fractures set-2 (having orientation ESE- WNW ( S45°E to S75°E)). Results show that the dextral shear along the ENE-WSW to E-W trend reflects the majority of the analyzed fault-slip data. Plane surfaces of these dextral strike-slip faults are coated with calcite steps and/ or soil staining, suggesting water infiltration and potential dissolution processes. Thus, it can be said that fractures represented by the neoformed dextral strike-slip faults and release joints have been reactivated later and the structural control of the karst development along these structural elements is present in the hard carbonates of the study area.