AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Three-Dimensional Structural Evolution of a Salt-Cored, Domed, Reactivated Fault Complex, Jebel Madar, Oman
(1) Geology and Geological Engineering, Colorado School of Mines, Golden, CO.
The Late Cretaceous fractured carbonates of the Middle East contain some of the world’s largest hydrocarbon reserves. Besides matrix permeability and porosity, reservoir quality is highly dependent on fracture distribution. The northern Oman region has a complex tectonic history, and multiple major tectonic events affected the area.
This study provides a three-dimensional structural evolution of the Late-Cretaceous outcrops of a salt-cored domed structure containing reactivated faults (Jebel Madar) that crop out in the Adam Foothills of Northern Oman. A multi-layered, integrated, three-dimensional, numerical structural model of the study area was built to determine the impact of multiple major tectonic events to the fault and fracture distribution in the study area. Data types and scales include: geologic field mapping, photo-realisitic LiDAR models, high-resolution Quickbird imagery, depth elevation models, and seismic and well-log data.
Analysis of the structural evolution of Jebel Madar show that three major tectonic events with different stress regimes resulted in a complex domed structure containing reactivated faults. NE-SW oriented graben- and half-graben structures formed as a result of initial local dome-formation, due to SW-verging compression of the Late-Cretaceous obduction of the Hawasina Complex and Semail Nappe to the N-NE of the study area. Seismic interpretation shows that the imbricates of the allochthonous Hawasina Complex were deposited across the study area, causing burial of approximately 1 km, and resulting in initial fluid release and calcite formation as fault infill. Early Paleocene obduction of the Masirah ophiolite, east of the study area and the opening of the Gulf of Aden, led to a NW-verging transtensional stress regime that caused E-W oriented oblique normal fault formation, cross-cutting pre-existing faults in the study area. Lastly, the Miocene Alpine orogeny resulted in growth of the Oman Mountains north of the study area and a foreland basin formation in the Adams Foothills that led to local dome-formation by reactivation of the pre-existing faults, and salt-diapirism as a result of differential loading. This event is marked by clear down-dip slickenlines on the fault surfaces, fault breccia containing a mix of calcite and blocks of older stratigraphy, and locally reactivated folding.