Evidence for and relationship between recent distributed extension and halokinesis in the Farasan Islands, southern Red Sea, Saudi Arabia

Abstract

This paper presents a structural evolution study of the Farasan Bank using an integration of field work, remote sensing data, and regional Bouguer gravity data interpretation. The architecture of the Farasan Islands is influenced by normal faults parallel to the Red Sea rift axis delineating a series of graben and asymmetric half-graben structures as well as salt domes. Geological data suggest that the negative gravity anomaly over the Farasan Bank reflects thick salt deposits. The gravity data shows a general NW-SE trend with the main negative anomaly coincident with the Farasan Islands. Gravity data together with seismic reflection data suggest that salt diapirs are elongated and parallel to the main rift orientation (NW-SE). This indicates that salt deposition and diapirism was controlled by rift-related basement structures. Forward modeling of gravity data constrained by marine seismic reflection interpretation reveals that the evaporites directly overlie the basement in most places. No pre-evaporite formation was detected. Integration of the modeling with field observations and interpretations suggests that the Farasan Islands are in an area of active extension. Extension and salt diapirism on the flank of the mid-ocean ridge is likely to be synchronous with renewed spreading at 5 Ma.