Methods of forming a geologic map usable for identifying prospective resource accumulations beneath the earth-surface are disclosed herein. The methods include obtaining a seismic stratigraphic structure of a subsurface region of the earth, determining a plurality of potential resistivity boundaries from the seismic stratigraphic structure, obtaining an electromagnetic data set resulting from an electromagnetic data acquisition of the subsurface region, recovering a resistivity map of the subsurface region by performing an inversion process guided by the seismic information, and resolving a geologic map from the resistivity map.