Sediments

Sediments are subdivided into three types:

• Clastic or detrital sediments comprising particles of various sizes carried in suspension by wind, water or ice. Sand is an example of a clastic sediment. Silt and saand size particles are carried in suspension by wind, water and ice.
• Chemical or precipitated sediments which are carried in aqueous solution. Salt (halite) is an example of a chemical precipitate.
• Organic or biogenic sediments, precipitated or accumulated by biological agents. Many organisms promote the precipitation of calcite to form biogenically precipitated calcareous muds.

Sediments are classified on the basis of the origin, size and mineralogical composition of the particles. They are produced by the action of weathering and erosion that break down pre-existing rocks by physical and chemical processes. The sediment is then transported by wind, water or ice to the site of deposition.

The character of the sediment is determined by the extent of weathering and the type and distance of transportation. Some sediments are weathering in place with little or no transport (eg. laterites). Others may be transported over vast distances from mountain top to ocean.

The transport agents wind, water and ice generate distinctive sediments that can be identified by the extent of particle abrasion and the degree of sorting.