Solid bitumen in calcite veins from the Natih Formation in the Oman Mountains: Multiple phases of petroleum migration in a changing stress field

Solid bitumen in calcite veins in Natih limestone on the southern flank of the Jebel Akhdar Anticline provide evidence for at least two previously unrecognized petroleum migration events in the Oman Mountains. We present field observation of bituminous calcite veins combined with microscopy using highly polished thin sections. This allows imaging of solid bitumen in reflected light and study of its microstructural context in transmitted light. Straight and en échelon, black impregnated, bedding-normal Natih A calcite veins strike 110°. They formed as one of the earliest structures in an extensional stress regime at the end of Cretaceous (Turonian–Santonian) either by flexure of the Arabian plate (Wasia–Aruma break) or by subsidence during subduction. The veins always contain planar arrays of small (