Lithostratigraphy and Microfacies Analysis of the Ajlun Group (Cenomanian to Turonian) in Wadi Sirhan Basin, SE Jordan

The Ajlun Group of the Wadi Sirhan Basin, Jordan, of probable Cenomanian- Turonian age, consists of alternating beds of indurated marl, marly limestone and dolomitic limestone with violet friable phosphatic sandstone. The results were used to develop a new lithostratigraphic correlation of the undifferentiated Na’ur, Fuheis, Hummar and Shueib Formations and Wadi Sir Formation in the study area. The stratigraphic boundaries of these units were defined at marked changes in outcrop and borehole characteristics. They are 25.5 metres thick at outcrop of Zgaimat Al-Hasah and 147 metres in the Wadi Sirhan-2 well. Microfacies analysis indicates deposition in a near shore slightly restricted shelf lagoon (packstone-wackestone) to more restricted environment represented by pure micrite. They are arranged in four shallowing cycles of relative sea level change. The very low thickness of the Ajlun Group at Zgaimat Al-Hasah (25.5 metres compared with 100s m elsewhere in Jordan) as well as the restricted near shore environments are explained by deposition on the Bayer-Kilwa paleohigh which left little accommodation for the deposition of the Ajlun Group.