The Jinadriyah anticlines: a surface model for oil fields in eastern Saudi Arabia

Mesozoic oil in Saudi Arabia exists in north/south-oriented anticlines. Such anticlines are usually studied using subsurface data. The present study introduces, for the first time in Saudi Arabia, a surface analog for these anticlines. The study covers two northerly oriented anticlines located in the Jinadriyah area at 15 km to the northeast of the Riyadh city. They are named herein the North and South Jinadriyah anticlines. The outcrops in both anticlines belong to the Lower Cretaceous Yamama Formation which consists of limestone in its lower part and limestone with shale in its upper part. The study included initially detailed interpretation of Google Earth and Landsat TM images to map the structural pattern of the anticlines. Detailed field mapping confirmed the satellite image interpretation and helped describe the geometry of the two anticlines in detail. The 3.5-km-long South Jinadriyah anticline is an open doubly plunging asymmetric anticline. The western flank is dissected by 13 minor reverse faults of north–south orientation. The North Jinadriyah anticline is about 5.5 km long and is relatively more complex than the South Jinadriyah anticline. It consists of northern, central, and southern segments that differ from each others in orientation and style. The anticline is dissected by 18 minor faults of different orientations and sense of displacement. Two perpendicular fracture sets with one being parallel to the anticline axes were recorded in the two anticlines. Both anticlines are interpreted as fault-propagation folds that were formed during the Late Cretaceous first Alpine orogeny. The mid-Late Tertiary second Alpine orogeny and Late Tertiary eastward tilting of the Arabian Plate increased the degree of folding and faulting.