Unconsolidated dune sands typically occur on the ocean beaches. These consist of loose sand and shell fragments that have been influenced by wave action, tides, and wind. In a few areas, such as Floras Lake, the substrate consists of small pebbles. Bullards soils are well drained and occur in areas dissected by streams.
Bandon soils are also well drained and occur in broad, gently to moderately sloping areas.
The soil of interest is the Blacklock soils. These deep, poorly drained soils occur in depressional areas of marine terraces. They have a highly organic topsoil with a cemented hardpan approximately 18 inches below the surface. Permeability of water through this cement-like soil is very slow. This hardpan perches water and creates many of the wetlands in the area.