oa Impact of South Oman Salt-Halokinesis from Fault Interpretation

Since Precambrian, Oman region has been influenced by many tectonic regimes that resulted in<br>different structural styles. The type and amount of tectonics vary significantly across Oman. As a<br>result, a number of structural domains can be easily defined in south, central and north Oman. The<br>presence and thickness variation of the underlying Ara salt is one of the key parameters used to define<br>these domains. In places where salt is absent or very thin, the effect and timing of far field regional<br>tectonics can be clearly demonstrated (e.g. Lekhwair High). However, in areas where the salt is very<br>thick, the impact of far field regional stresses is often difficult to distinguish from the local effect of salt<br>withdrawal and salt dissolution.<br>In south Oman, salt halokinesis has dominated the deformation style and orientation of local stresses<br>in Palaeozoic times. This resulted into a tortuous framework of salt domes, ridges and depression<br>which have influenced any younger deformation events. Initially, sediments were deposited in local<br>depo-centres (e.g. named as pods) and simultaneous differential loading and salt dissolution is<br>interpreted to have been the main driving mechanisms of the deformation. It is important to note that<br>the deformation is happening without external regional far field driving stress regime. The final pod<br>geometries is directly controlled by sediment supply, space accommodation and initial salt thicknesses.<br>With ongoing thinning of the salt, the pods grounded progressively. Loci of depo-centres migrated<br>following the salt availability. The most typical structures formed during this time are turtle-back<br>anticlines, with extensional faults dipping away from the centre of the anticline. Surrounding these<br>turtle back anticlines, narrow collapse graben structures have developed above salt ridges/domes<br>(thick salt area) as a result of salt removal. Across South Oman, a number of depression at the present<br>surface topography formed above the deep thicker salt area, indicating that salt removal is still<br>continuous today.<br>The presentation will concentrate on the early Palaeozoic halokinesis. We will illustrate the regional<br>structural models with a series of key observations as well as demonstrate how the structural model<br>can be used to help seismic fault interpretation, especially in area of poor seismic quality.