Barrier island

Depth of water

(Land) - High tide

Circumstances

Narrow and long islands parallel to the seashore at a few km from the coast. Modern barrier islands are at coasts of Gulf of Mexico and Atlantic coast of North America. The foreshore of longshore bars got left by erosion of invaded sea. Barrier islands are formed along the coast under the following conditions: 1) in the process of marine transgression, and 2) tide range is less than 4 times of the averate wave height.

Sedimentary facies (Sediments)

Foreshore sediments at the ocean side coast. Gravels and shells may be concentrated at the bottom of ocean side sediments. Muddy sediments with traces of plants at the lagoon side. Tidal channel sediments at tidal channels between barrier islands.

Sedimentary facies (Structures)

Hummocky cross-stratification by waves, planar cross -stratifications gently inclined to the sea side, swash / low angle wedge-shaped cross-stratification, and parallel stratification. at the ocean side coast.