Interpretation of microgravity and magnetic data for delineation of subsurface salt bodies in unfavorable S/N ratio conditions

It is well known that salt bodies occurring in subsurface usually are unfavorable targets for gravity and magnetic methods application. It is caused mainly by small differences in density (salt layers with a density of 2100-2200 kg/m³ often occur in sediments with the similar density) and magnetic (salt layers with a magnetization of about -10 mA/m as a rule occur in low-magnetic media) properties as well as geological-petrophysical variability of the subsurface geological section. Therefore, for gravity-magnetic data processing and interpretation in general should be applied many advanced procedures from the available methodological arsenal, beginning from removing of different kinds of noise and target visual localization, and ending with development of 3D physical-geological models of the medium. Despite the fact that quantitative analysis of gravity-magnetic anomalies from salt objects, usually having a form of thin horizontal plates is a complicated problem, an interpretation methodology for careful analysis of observed potential field anomalies has been recently developed (Eppelbaum, 2014b). Integration of gravity and magnetic data between themselves and with other geophysical methods increase reliability and accuracy of geological-geophysical interpretation. For combined 3D gravity-magnetic modeling is applied the developed GSFC software where the geological bodies are approximated by 3D horizontal polygonal prisms. Application of some qualitative and quantitative interpretation methods is shown on model and field examples. Besides the land survey, it is proposed to apply remote operated vehicle magnetic survey at low altitudes, which will allow not only to delineate salt targets disposition, but also to monitor appearing new karst terranes often associated with salt objects.