The July oil field is a major normal-fault–bounded structural block in the Suez rift basin, Egypt. It is adjacent to a major structural transfer zone, which has controlled sediment influx to the rift basin center for the past 20 m.y. The lower to middle Miocene Upper Rudeis Formation, part of the synrift stratigraphic sequence, records deformation of the July structural block. The formation contains abrupt lateral changes in thickness and facies, which record earlier phases of fault movement and deformation in the July field area that do not conform to the present-day structural configuration.
The Upper Rudeis Formation was deposited as turbidites in a submarine-fan system sourced from the western rift shoulder. It was deposited over and around bathymetric highs created by coeval fault displacement in the July field area. By studying thickness and facies patterns, we have determined that the present-day main bounding fault to the July block consisted of a series of unlinked fault segments, which linked after Upper Rudeis deposition. A subsidiary fault west of the block exerted the most control on thickness patterns, not the present-day main bounding fault. Thus, commonly used models of deposition in active half grabens are difficult to apply at July field.