During high-energy periods in the fortnightly cycle (i.e. most spring tides), a cross-laminated sand layer is present at the seabed surface that exhibits varying degrees of bi-directional current structure and contains low porewater salinities. During low-energy periods in the fortnightly cycle (i.e., most neap tides), a mud bed forms at the seabed surface in association with fluid muds in the water column. The mud beds are subject to resuspension and deposition by semidiurnal tidal currents that form thin sandy interlaminations. Interlamination and interbedding of sand and mud result from the combination of estuarine and tidal processes at the river mouth. The fine- and coarse-grained beds are both preserved, forming interbedded (alternate layers > 1 cm in thickness) muds and sands. The thickness of the fortnightly beds is dependent upon monthly variations in spring/neap amplitudes.