Propagation history and passive rotation of mesoscale normal faults: implications for synrift stratigraphic development

Field data from onshore exposures of the Oligo‐Miocene Gulf of Suez Rift in the Sinai document the passive rotation of early formed mesoscale synthetic and antithetic faults and associated half‐graben due to long‐lived activity on large displacement (2–5 km) block‐bounding faults. Early formed small‐displacement (<350 m) mesoscale antithetic faults and half‐graben within regional‐scale fault blocks underwent progressive steepening due to footwall uplift, rotational faulting and footwall flexing on large‐displacement, block‐bounding faults. In contrast, mesoscale synthetic faults were progressively rotated to shallower angles. Analysis of palaeohorizontal surfaces within synrift sediments deposited in half‐graben adjacent to the mesoscale faults indicate passive rotations of up to 25° about horizontal axes since deposition. Passive burial and in‐filling of early formed mesoscale faults and half‐graben by synrift sediments is consistent with extension being transferred from numerous mesoscale faults to few block‐bounding macroscale faults as extension preceded. Furthermore, this transfer of extension appears to be associated with a marked change in basin configuration, synrift sediment dispersal patterns and facies development. Identification of early formed, passively rotated normal faults and half‐graben is important for correctly reconstructing the early stages of basin palaeogeography and sediment dispersal, and for addressing models of rift basin evolution.