Figure 6 (on this and following page). Filtered (A) magnetic, (B) gravity, and (C) basement gravity maps. Black circles—maximum directional derivatives (size is proportional to magnitude); white bold dashed line—crustal boundary on southeast side of V-shaped basement gravity high (Ponce and Glen, 2002; Grauch et al., 2003b; Ponce, 2004). See Figure 1 for additional explanation.