Fig. 3. Back-scattered electron scanning images: (a) topsoil (Ap horizon), (b) 25- to 35-cm subsoil (E horizon), and (c) 40- to 50-cm subsoil (Bt horizon). Voids occupied by resin are black, homogeneous gray areas are quartz grains, very light particles in the silt range size are much heavier mineral than quartz, and heterogeneous gray areas are fine silt and clay particles and associated porosity (bar scale = 1 mm).