Deltas are fan-shaped deposits formed where a river flows into a standing body of water, such as a lake or sea. Some well known deltas include the Mississippi River delta and the Nile River delta. Beaches and barrier islands are shoreline deposits exposed to wave energy and dominated by sand with a marine fauna. Barrier islands are separated from the mainland by a lagoon . They are commonly associated with tidal flat deposits.
Lagoons are bodies of water on the landward side of barrier islands.
Lagoons are also present behind reefs, or in the center of atolls. Tidal flats border lagoons. Tidal flats are areas of low relief, cut by meandering tidal channels. Intense burrowing is common. Stromatolites may be present if conditions are appropriate.