Beach Depositional Environments

Inden and Moore (1983) defines beaches as wave-dominated systems. Beaches can occur attached to land or rimming leeward and/or windward sides of islands. They can occur anywhere on a platform where there is an area above sea level that is exposed to moderate-to-high wave energy. They are not unique to any one area.

The beach system can be divided into several depositional environments:

(1) Beach Backshore: Back sides of beaches can be dominated by several environments including eroded storm berms, eolian dunes, washover fans, supratidal flats, and pond sediments. (2) Back Beach: Composed of bankward tilted planar wedge sets with some trough crossbeds where water is funneled along the trough of the back beach. (3) Fore Beach or Foreshore: Forms in the swash zone and is composed of seaward dipping planar wedge sets of thin, even laminae where the sediment is sand sized. Keystone vugs created by trapped air are a commonly characteristic of this facies. Beaches can be composed of gravel to boulder-sized material where they are located landward of a source of coral. (4) Beach Shoreface: Forms in the surf zone producing wave-breaker bars that are oriented obliquely to the shoreline and generate medium-scale, trough crossbeds. (5) Beach Offshore: This is a lower energy environment where biological processes become more important than physical processes. Bioturbated sands to muddy sands are deposited.

Beach rock, produced by cementation in the surf/swash zone, is a common feature on carbonate beaches. It appears as lithified seaward dipping beds.

Fine-grained, high-energy ooid beach facing the open sea in Cancun, Mexico. High-energy beach composed of coarse coral debris on the east side of Bonaire (southern Caribbean) facing the open sea.

Beaches can occur in many different locations on the platform. Several examples are shown below.

click on beach type to see example photographs

Rock types:

Pleistocene outcrop of a shoreface (trough crossbedding) and foreshore-beach bedding (seaward dipping planar wedge sets) from West Caicos Island in the Turks and Caicos Islands.