Gravity Survey over Jabal Hafit - Implications for Basement Configuration of the Frontal Fold Belts of Oman Mountains

A gravity survey was carried out in and around Jabal Hafit, south of Al Ain, Abu Dhabi in the United Arab Emirates. Jabal Hafit is a 30 km long and 4.5 km wide asymmetrical, double-plunging, NNW-SSW trending anticline which consists of shallow-marine carbonates of Eocene to Miocene age trending parallel to the Oman Mountains. The area is of tectonic significance because the reactivation of basement faults are believed to control distribution of hydrocarbon traps. Results from the gravity data constrained by outcrop geology, confidential well and seismic data and bedrock density measurements, have been used to determine the subsurface structure of the study area. NNW-SSE trending positive residual gravity anomalies of up to +6 mGal occur on the Jabal Hafit and Al Ain anticlines. These positive gravity highs are attributed to basement horsts as the structural style is considered to have resulted from reactivated deep-seated fault blocks. The residual Bouguer anomaly values decline gradually to the east and west of Jabal Hafit as the basement deepens. A large negative gravity anomaly of <-5 mGal is observed east of Jabal Hafit and coincides with a syncline which caused thickening of the Upper Cretaceous and Tertiary sequences.