Evidences for Inversion and Strike-slip Structures in Al Majma’ah Fault Zone, Northern Part, Northwest of Al Majma’ah City, Central Saudi Arabia

A.O. Bamousa¹, A.M. Memesh², and S. Dini²

Abstract

The Al Majma’ah fault zone is a large tectonic feature, located about 200 Km north west of Riyadh; it extends for about 142 Km from west of Al Majma’ah city to the southwest of the Al Artawiyah town, and it is 2 km in width, in which it has been mapped at 1:250,000 scale in the Shaqra and the Al Artawiyah quadrangles. Detailed mapping and interpretation of the northern part of the Al Majma’ah fault zone have been carried out during field investigation, using Landsat ETM+ and DEM data, for the northern part of the Al Majma’ah fault zone, between lat 26 and lat 26°45', within the Al Artawiyah quadrangle. In this study, we present data, suggesting that the Shaqra open fold extends northward, and bound by the Al Majma’ah fault zone, west of Al Artawiyah town. The data also suggests presence of a narrow synclinorium, bound by the 2 km width of the fault zone, with minor thrust faults that trend N-S and dip towards to west. Kinematic indicators in eastern and western margins of the fault zone suggest sinistral movement, associated with minor compressional movement. This suggests that the Al Majma'ah fault is a sinistral fault zone. The strike-slip movement faulted the Wasia' Formation rocks against Arumah Formation rocks, in the eastern and western margins of the fault zone. This suggests that the age of Al Majma’ah strike-slip fault, and the related anticline and synclinorium, are Late Cretaceous to Early Paleogene. The fault is divided into enchlon structure due to cross-cutting E-W Paleogene to Quaternary dextral faults. These faults are associated with E-W minor folds that deformed the quaternary deposits.

AAPG Search and Discovery Article #90188 ©GEO-2014, 11th Middle East Geosciences Conference and Exhibition, 10-12 March 2014, Manama, Bahrain