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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

4D Evolution of the Maradi Fault System, Oman

Abdullah Al-Gahaffi1; Ken McClay1

(1) Department of Earth Sciences, Royal Holloway, University of London, Egham, United Kingdom.

The 4D evolution of multiphase strike-slip fault systems is generally poorly understood due to the structural complexities that develop along their strike, and their steep fault and stratal dips that are commonly poorly imaged in seismic surveys. The Maradi strike-slip fault system in Oman is an important 60 km long dextral strike-slip fault system that is poorly exposed. In the subsurface it is associated with a number of major hydrocarbon accumulations. In this paper the main elements of the Maradi fault system have been simulated using scaled analogue modelling. Both wet clay and dry sand analogue modelling experiments have been run to simulate deformation in a sedimentary cover sequence above releasing and restraining step-overs in a basement strike-slip fault system. The experiments were monitored by high-resolution time-lapse photography as well as digital laser scanning and by PIV monitoring. In this way the surface topographies were monitored (laser scanning) as well as detailed particle displacements and strain histories were measured (PIV monitoring). In the releasing step-over experiments an elongate rhomboidal pull-apart graben was developed between the offset Principal Displacement Zones (PDZs). Terraced oblique-slip extensional sidewall faults system developed along the boundary of pull-apart basin. These sidewall faults changed kinematics along strike, from oblique-slip near the PDZs to extensional slip in the middle of the structure. A cross-basin fault system cut the flat bottom of the pull-apart basin and linked to the offset PDZs.

In the restraining step-over model a lozenge-shaped ‘pop-up structure’ developed. This was bounded by two sidewall, oblique-contractional faults that were arcuate in shape and curved inwards toward the main basement faults. At the end of the experiment, the retraining step-over offset PDZs were linked by a sinistral trans ‘pop-up’ strike slip fault. Detailed displacement analyses and strain analyses are presented to illustrate the progressive evolution of the structures. The results of the scaled analogue modelling are compared to natural examples of strike-slip structures along the Maradi fault system in Oman.