oa Tectonic Escape (Indentation) in Central Saudi Arabia, Possibility and Exploration Potential

Tectonic analysis indicates a high possibility of tectonic escape structures in central Saudi Arabia which<br>could bear significant hydrocarbon exploration potential. This study aims to introduce a new tectonic<br>model that explains several surface and subsurface newly mapped structures in central Saudi Arabia.<br>Potential fields, seismic and surface geology data are integrated to accomplish this study.<br>Basement terrane analysis of the Arabian shield and its eastern continuation beneath the sedimentary<br>basin indicates the general north-south orientation with differences in width and composition. It shows<br>that the maximum crust thickness is in the middle of the outcroping shield with a promontory<br>extending 200km toward east in subsurface (Central Arabian Arch) where Triassic (Khuff) marine<br>carbonates overlay the basement directly. The crust shows gradual thinning eastward from this<br>promontory till the offshore Arabian Gulf. Some terranes show wedging-out and others show narrowing<br>against the eastern side of the basement outcrops. This pattern suggests the tectonic escape of the<br>wedging out and narrowing terranes against the competent Afif terrane since the InfraCambrian<br>accretion of Arabia. The terrane accretion occurred by westerly driven terranes collided against the<br>thick promontory of the Afif terrane causing dispersion toward south and north through east-west<br>accommodation zones. Long segments of unusual east-west surface structures (faults and strike of<br>strata) over the boundaries of the subsurface basement promontory from north and south are thought<br>to be a dragging of the dispersed terrane fragments at the promontory boundaries. West of these eastwest<br>zones, deformation is concentrated at the north-south terranes with curved hard link transfer<br>zones. This InfraCambrian tectonic setting is believed to have been reactivated during Phanerozoic<br>tectonic phases to express its escape tectonics pattern further-up till outcrops. Re-distribution of the<br>Phanerozoic stresses at that inherited basement fabric controlled the geometry of the sub-basins and<br>their filling during extension phases. It controlled also the preferable locations of structural positive<br>inversion during compression phases to form the fault related fold traps. This approach explains the<br>diversity of structural styles in the sedimentary cover (compression, transpression, and transtension)<br>which formed simultaneously during Late Cretaceous compression but with different directions.