Analysis of Mesostructures along Jarash- Irbid Highway, Northern Jordan

Geologic structural surveys were conducted in many road cuts and quarries along the Irbid-Jarash highway, north of Thughart Asfour village. Meso-scale tectonic structures which were found in these stations including: folds, faults (Strike-slip, normal and reverse), joints, flower structures, boudinage structures and shear fractures, revealed that the area has undergone a local tensional as well as compressional stresses related to the regional one. More than 1385 fracture measurements were done using scanline, circle, and common methods in order to investigate the orientation and density of the fractures in different parts of the study area. Two dominant trends of joint sets (N-S and NNW to NW) and other minor trends (E-W, ENE-WSW and WNW-ESE) were found in the Cretaceous carbonate rocks (Wadi Es Sir Limestone Formation). The dominant trend sets represent the range of conjugated, hybrid, and extensional fractures in which the acute bisector of these represents the main trend of extensional fracture set, which in turn is consistence with the SHmax (maximum horizontal compressive stress axis) oriented NNW-SSE. Geometries of fractures in the carbonate rocks represent a continuum of structures at various stages of development that can be classified into two main geometric categories corresponding to increasing levels of brittle strain; bed- confined fractures and throughgoing fractures. Many throughgoing fractures develop subsequent to bed-confined joints by the coalescence of pre-existing joints. The spatial distribution of throughgoing fractures varies as a function of structural position. The highest frequency and estimated strain intensity have been located at the fold crests and fault zones.