AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Impact of South Oman Salt-Halokinesis from Fault Interpretation
(1) Study Centre, PDO, Muscat, Oman.
Since Precambrian, Oman region has been influenced by many tectonic regimes that resulted in different structural styles. The type and amount of tectonics vary significantly across Oman. As a result, a number of structural domains can be easily defined in south, central and north Oman. The presence and thickness variation of the underlying Ara salt is one of the key parameters used to define these domains. In places where salt is absent or very thin, the effect and timing of far field regional tectonics can be clearly demonstrated (e.g. Lekhwair High). However, in areas where the salt is very thick, the impact of far field regional stresses is often difficult to distinguish from the local effect of salt withdrawal and salt dissolution.
In south Oman, salt halokinesis has dominated the deformation style and orientation of local stresses in Palaeozoic times. This resulted into a tortuous framework of salt domes, ridges and depression which have influenced any younger deformation events. Initially, sediments were deposited in local depo-centres (e.g. named as pods) and simultaneous differential loading and salt dissolution is interpreted to have been the main driving mechanisms of the deformation. It is important to note that the deformation is happening without external regional far field driving stress regime. The final pod geometries is directly controlled by sediment supply, space accommodation and initial salt thicknesses. With ongoing thinning of the salt, the pods grounded progressively. Loci of depo-centres migrated following the salt availability. The most typical structures formed during this time are turtle-back anticlines, with extensional faults dipping away from the centre of the anticline. Surrounding these turtle back anticlines, narrow collapse graben structures have developed above salt ridges/domes (thick salt area) as a result of salt removal. Across South Oman, a number of depression at the present surface topography formed above the deep thicker salt area, indicating that salt removal is still continuous today.
The presentation will concentrate on the early Palaeozoic halokinesis. We will illustrate the regional structural models with a series of key observations as well as demonstrate how the structural model can be used to help seismic fault interpretation, especially in area of poor seismic quality.