The Marine-Dune Transition
In other cases the transition is marked by protosol (type 2), which suggests the growth of vegetation over the marine sediments prior to dune deposition. At some locations the two types of upward transition co-exist along the same marine-dune contact; ie the protosol thins in the seaward direction and then disappears. The inference here is that a dune formed nearshore on a prograding beach where there was little vegetation and no soil; and that, in landward growth, the dune subsequently buried a weak soil which had formed in it's lee.
Where Pleistocene dunes emerge laterally with high marine deposits (type 3) the more typical seaward progradation of sedimentation did not occur or was interrupted due to ceasation of dune building when sea level was at it's maximum level.
The three types of marine-dune transitions, just described,
refer to only the marine and dune deposits of the same Formation, ie. those
that are considered to belong to the same episode of sediment accumulation.
Where there is a substantial time gap, different types of disconformable
relationships are possible.