Modeling basin geology in a subsurface region includes receiving seismic data representing acoustic signals that are reflected from regions of the subsurface; receiving potential fields data comprising potential field values that are mapped to locations in the subsurface; determining a relationship between the seismic data and the potential field values for each of the locations in the subsurface; generating, based on the relationship for each location, a three-dimensional (3D) map of thermal conductivity in the subsurface region; and based on the 3D map of thermal conductivity, identifying at least one area comprising source rock having a threshold maturity, the threshold maturity indicative of potential hydrocarbons in the subsurface.