Sand spit, Longshore bar

Depth of water

(Land) - High tide

Circumstances

Deposits of sands and gravels transported and formed by longshore currents parallel to the seashore. The long and narrow deposit is approximately parallel to the seashore lines. Sands and gravels are supplied from rocky coasts and rivers nearby. Generally sand spits and longshore bars grow from a point of the seashore. Longshore bar is used in case both sides are almost contacted to the seashore, and sand spit is used in case only a side is contacted to the seashore. Bar is the deposit of sands and gravels formed by currents to a direction, and observed not only seashore but also lakes and rivers.

Sedimentary facies (Sediments)

Composed of upward-fining sands and mud, and sands with plenty of shellfish fossils. Foreshore sediments. Tidal channel sediments at tidal channels at the gap between the longshore bar and the seashore.

Sedimentary facies (Structures)

Strongly influenced by tide. Hummocky cross-stratification by waves, planar cross -stratifications gently inclined to the sea side, swash / low angle wedge-shaped cross-stratification, parallel stratification.