TECTONIC AND STRUCTURAL EVOLUTION

Abstract

The available geological information including stratigraphic sequence, unconformities pattern, drill-hole data, seismic and structural elements have been integrated to infer the tectonic and the structural evolution of the Iraqi Western Desert. The Western Desert is a part of the northern Arabian Platform, where relatively thin Phanerozoic sediments cover the Precambrian N – S and NW – SE fractured continental basement complex. The platform itself is divided into two parts, a stable one to the west (within which the Western Desert is located) and an unstable one to north and east. The boundary between the two parts of the platform is taken along Anah – Abu Jir Fault Zones. The Paleozoic sequence is dominated by silici-clastic sediments deposited in a shallow epicontinental sea in a relatively stable conditions, whereas the Mesozoic sequence show a major change in the depositional system from a primary silici-clastic Paleozoic regime to a major carbonate deposition with interspersed clastic episodes. However, the Cenozoic sequence displays gradual retreat of the sea and final transition to the continental conditions. Structurally, the two major Paleozoic orogenic movements (Caledonian and Hercynian) were identified by their effects on sea level changes rather than their orogenic deformation. On the other hand, however, the sedimentation pattern through most of the Mesozoic era was a reflection to a fluctuating sea level and periodical movements of Hail – Rutbah Arch. Nevertheless, by the late Tertiary a significant tectonic activity took place along the boundary of the stable/ unstable parts of the platform, causing the structural inversion of Anah Graben, and a limited right lateral strike- slip movement on Abu Jir Fault Zone. Finally, conclusive evidences on the nature of Hauran Fault System as well as the recent activity along Anah – Abu Jir Fault Systems are introduced.