Useful Terminology

Delta
A large fan-shaped area of silt deposits found at the mouth of a river where it enters a sea or lake. A triangular area of deposited silt or alluvium at the mouth of a river. It will occur where a river carries a heavy load and empties into a shallow sea. As the area of silt increases the river tends to divide into many smaller channels.

Lagoon
A body of shallow water of varying salinity wholly or partially separated from the sea by some form of barrier, such as a sand bank (or reef).

Bottomset beds
Layers of the finest load (clay) that is deposited at the seaward edge of the delta. These particles are transported by suspended load being carried out the furthest by the river and are deposited when the river has little or no remaining energy at the seaward edge of the delta

Foreset beds
Layers of bedload, including the largest sediments (pebbles & sand) that roll along the river channel. The bedload rolls over the edge of the delta and builds up a steep angled layer on top of the bottom set beds as the main delta advances. These course materials at the advancing front of a delta form the bulk of the delta.

Topset beds
Horizontal layers of smaller sediments (silt & clay) that overlay the foreset bed. The suspended load settles out into horizontal beds over the top of the delta.