DEFINITION OF GRAVEL

A natural accumulation of rounded sedimentary

particles, with the majority being larger than sand (.08 inch,

or 2 mm). The particles may include granules, pebbles, cobbles,

and boulders in increasing size, and the gravel may be

named according to the size or composition of its most abundant

particles or by its matrix. When consolidated, gravels

are known as conglomerates. Conglomerates as gravels are

said to be oligomictic if they are composed of one type of

clast, and polymictic if they are composed of clasts of many

different types.

Gravels are commonly found in streams and on beaches

and cover some alluvial plains and alluvial fans in arid

regions. They are deposited in places where fast currents lose

velocity and can no longer transport them. Many gravel

deposits are only temporarily in place, such as those in

streams, and may only move during flood events.

Reefs and other carbonate environments produce coarsegrained

limestone or coral conglomerates and breccias, but

these types of rocks are usually classified as limestone-breccias,

carbonate conglomerates, and other types of carbonates.

Some unusual types of gravel and conglomerate include

tillites, coarse glacially derived gravel and conglomerate typically

in a fine-grained matrix, and diamictite, a nongenetic

name for a non-sorted, non-calcareous terrigenous sedimentary

rock composed of sand and larger-sized particles in a

fine-grained matrix.

See also SEDIMENTARY ROCKS.

Title Post:
Rating: 100% based on 99998 ratings. 99 user reviews.
Author:

Terimakasih sudah berkunjung di blog SELAPUTS, Jika ada kritik dan saran silahkan tinggalkan komentar