3-D gravity and magnetic interpretation for the Haifa Bay area (Israel)

Recently observed features in the subsurface geology of the Haifa Bay area (northern Israel) have been evaluated using 3-D forward gravity and magneti c modeling and inversion schemes. The interpretation is based on updated pe trophysical data of the Jurassic, Cretaceous and Tertiary sedimentary layer s and volcanics. It has been shown that the Bouguer gravity anomalies corre spond mainly to thickness variations in the Senonian to Tertiary sediments. The gravity effect of these sediments was calculated using their actual de nsities and structural setting as interpreted from seismic reflection data. This effect was removed from the Bouguer gravity in order to study the pre -Senonian geological structures. The pattern of residual gravity anomalies (named "stripped gravity'') is essentially different from the pattern of th e Bouguer gravity. The prominent Carmel gravity high, clearly seen on the B ouguer gravity map, completely vanishes on the "stripped" gravity map. That suggests that this relatively positive anomaly is caused by the considerab le thickness of the low-density young sediments in the surrounding areas an d does not correspond to high-density magmatic rocks or crystalline basemen t uplift as previously suggested. The average densities of the Jurassic and Cretaceous volcanics are generally lower then those of the background sedi mentary rocks. Volcanics are the main cause for magnetic anomalies onshore and offshore northern Israel. The magmatic root of the Asher volcanics is, most probably, located close to the Yagur fault. A large, deep-seated gabbr oic intrusion is assumed to be located under the Mediterranean abyssal plai n in the NW part of the study area. The Atlit marine gravity low appears to be caused by a thick Mesozoic and Tertiary sedimentary accumulation. The r esults presented should be of considerable assistance in delineating some a spects of hydrocarbon exploration in the area. (C) 2000 Elsevier Science B. V. All rights reserved.