Intertidal Flats
Morphology
Gently sloping, broad surface
Flooded and exposed with the tide each day
Tidal Channels-dissect flat-may have water in them throughout tidal cycle
Sediment
Sand and mud (with some shelly material)
Highest energy is near base of intertidal zone, so it typically has coarser material
Grainsize decreases landward and upward across flat
Mud typically at the most landward reach (opposite of sandy beach environment)
Source is ocean side-fining inland
Similar conditions at a particular location = well sorted sed there.
Organisms
Benthic (living on/in the substrate)
Vagrants-snails mainly
Sessile-cyanobacterial mats (photosynthesis), oysters-attach to substrate and each
other, mussels, burrowers such as clams and worms
Cyanobacterial mats are important sediment stabilizers
Worms are bioturbators
Supratidal algal mats stabilize sediment washed up during storms
Mangrove plants often help stabilize mud islands
Limiters for organisms in the tidal flat: exposure (more pronounced in upper reaches), sediment
in the water (problem for filter feeders), sediment mobility
Sedimentary Structures:
Ripples, mudcracks, trace fossils, mixed mud and sand bedding, sand waves and
megaripples if significant tidal range
Processes
Tidal currents distribute sediment through the area
Simple model shows lag of flood and ebb energy moves particles landward.
Tidal channels typically cut into muddy sediment and show bidirectional water flow and
sedimentary structures (often lenses of sand/silt)