6 Jordan Journal of Natural History Geological evolution of the Azraq basin, eastern Jordan: An overview Abdulkader M. Abed Department of Geology, the University of Jordan, Amman 11942 Jordan
[email protected] ABSTRACT The Azraq basin is some 100 Km east of Amman, the capital of Jordan. Hydrologically, it occupies ~12700Km2, mostly in Jordan, but it also extends to southern Syrian and NW Saudi Arabia. The Azraq area seems to have developed as a basin during the Paleozoic testified by the total thickness of both Ram and Khreim Groups in the Azraq subsurface being slightly less than twice those in the southern outcrops. In this case, the Azraq basin is similar to the Wadi Sirhan basin. From the Carboniferous, Late Paleozoic, to the top Ajlun Group, Mid Cretaceous, no basinal development took place in the Azraq area. Dramatic changes seem to have taken place in the Azraq basin during the deposition of the Belqa Group. Northwest-trending faults became active since the Coniacian? such as the Fuluk Fault and Rajil Fault. A subsiding graben, called Hamza Graben, was the scene for a thick, fast sedimentation of more than 2000m during the Coniacian-Campanian represented by the Rajil, Hamza and Hazim Formation which are dominated by carbonates. This is explained by synsedimentary deposition in a subsiding basin. The basin continued up till the Eocene albeit being at a slower rate during the rest of the Belqa Group. By the end of the Eocene, the Neo-Tethys Ocean had migrated from the eastern Mediterranean and the Azraq area, as well as almost all Jordan, and the area became terrestrial, and subjected to erosion.