ABSTRACT
Sediment refers to both organic and inorganic loose material that is moved from time to time by physical agents including wind, waves, currents and gravity. The sediments found in coastal environments can be either imported from external environments (allochthonous) or locally produced (autochthonous). Allochthonous sediments are generally derived from the chemical and mechanical breakdown of continental rocks into grains that consist of either a single mineral or a subset of the minerals contained in the original rock. The two most common allochthonous minerals found in coastal sediments are quartz and clay minerals (e.g., illite, kaolinite, montmorillonite). Autochthonous sediments can include material derived from the breakdown of local rocky shorelines, but it is more common for such sediments to consist of grains derived from the body-parts of organisms living in the coastal zone and/or the chemical precipitation of dissolved minerals present in coastal waters. The most common autochthonous minerals are biogenic carbonate and silica. On a global scale, allochthonous sediments account for about 92% of sediment in the modern coastal zone and are delivered by rivers, glaciers, wind, and volcanic eruptions in decreasing order of importance (Open University, 1994).
