The upward growth of a tidal mudflat-marsh within the tidal frame is determined theoretically by the rates of minerogenic sediment supply, organogenic sediment supply, long-range sediment compaction and movement of relative sea-level. Where the movement of relative sea-level is upward, a marsh can achieve a state of dynamic equilibrium in which the composition of the sediment accumulating on its surface is governed by the balance between the rates of organogenic supply and sea-level change. A peat (organogenic) marsh should arise where the former rate roughly equals or exceeds the latter. A minerogenic marsh should form where the rate of sea-level rise is dominant, even though the absolute availability of mineral fine sediment may be so high as to appear to suggest that build-up to extreme tidal levels, where vegetation would dominate, should have occurred.
