Gravity and magnetic anomalies caused by deeply buried rock bodies in northwest Texas are compared. Interpretation of the gravity anomalies by modeling is used to locate and define the geometry of the body in a way analogous to the use of bathymetry in studies concerned with magnetization of seamounts. The direction of magnetization is then determined from the spatial relationship between the gravity and magnetic anomalies. This procedure amounts to an in-situ determination of direction of magnetization of the body. In one example direction of magnetization indicates the time of intrusion and in another it indicates regional heating since intrusion.