Figure 12: Photograph of a retreat placer deposit exposed by northward migration of the Willapa Bay tidal inlet at the southern end of the Grayland subcell. The placer deposit (2 m thick) was profiled in the subsurface by GPR and showed very strong "Boomer" reflections associated with iron-bearing (conductive) heavy minerals. The heavy-mineral placer lag occurs as multiple heavy mineral layers reaching 50 cm in thickness each. The maximum heavy-mineral concentration (greater than 50 percent by weight) occurs near the bottom of the erosional scarp (Woxell, 1998).