A NEW STRUCTURAL INTERPRETATION FOR THE EMPLACEMENT OF THE MASIRAH OPHIOLITES (OMAN) - A MAIN PALEOCENE INTRAOCEANIC THRUST

As shown by geological and structural mapping, the oceanic crust of Ma sirah Island is composed of two nappes. South vergent folds with E-W t rending axis, N-S stretching lineations and shear sense indicators are consistent with a shearing to the South of the Upper Masirah Nappe. T hrusting is bounded by late-Maastrichtian sediments below and middle E ocene shallow marine deposits which unconformably overlie the nappe pi le. The nappe pile and the Tertiary sediments were strongly affected b y extensional tectonics resulting in NNE-SSW trending horst and graben systems, resulting from N-S to NE-SW normal faults. These large scale structures are cross-cut by late E-W normal faults. The so-called ''m elange zone'' results from the interference between late normal faults and the flat lying plane of the Main Masirah Thrust (MMT) and does no t represent a major transform fault as previously assumed.