As shown by geological and structural mapping, the oceanic crust of Masirah Island is composed of two nappes. South vergent folds with E-W trending axis, N-S stretching lineations and shear sense indicators are consistent with a shearing to the South of the Upper Masirah Nappe. Thrusting is bounded by late-Maastrichtian sediments below and middle Eocene shallow marine deposits which unconfor-mably overlie the nappe pile. The nappe pile and the Tertiary sediments were strongly affected by 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 “mélangezone” results from of the interferenc between late normal faults and the flat lyingplane of the Main Masirah Thrust (MMT) and does not represent a major transform fault as previously assumed.