Delta plain

Synonym

Top set bed

Depth of water

(Land) - Continental shelf

Circumstances

Horizontal and flat plain formed by sediments on delta front. The delta plain under the sea is called delta terrace. Sediments are supplied when the river current speed is high during typhoon, for example. Fine sands in freshwater supplied from rivers deposit by mixing with heavy seawater at river mouth.

Sedimentary facies (Sediments)

Sands in delta at river mouth. Foreshore sediments in fan delta.

Sedimentary facies (Structures)

Tidal bandle, interbedded coarse sand and fine sand. Coarse sands deposit during rising and Ebb tides when seawater moves, and fine sands deposit at high and low tides when seawater does not move. Herringbone cross-stratification at the river mouth subjected to the strong tide. Herringbone cross-stratification is stacks of cross-stratifications having opposite directions, which are formed by rising and Ebb tides. Sediments subjected to strong bioturbation.