Glossary :: Sedimentology

Aragonite

A polymorph of calcite. Produced by many organisms as a shell, test or other hard part. Unstable at the Earth's surface and is very rare in ancient sediments.

Bed

A centimetre to decimetre layer in a stratigraphy. Beds can be massive or contain structures, such as cross bedding, ripple marks or laminations. Beds are grouped into formations. ...More

Bouma Sequence

The five part deposit produced by a waning turbidite flow. The deposit is split into:Structureless massive sand with gravel-rich erosional base.Parallel bedded sands produced by the upper flow regime.Cross laminated sands with ripple marks. Deposited in t...More

Breccia

A clastic rock composed of a matrix and angular clasts. A fine example of a breccia are the Devonian deposits at Siccar Point. See also conglomerate....More

Chalk

A fine grained, white calcium carbonate composed of coccoliths. Common in the Cretaceous of western Europe.

Chert

Microcrystalline silica (SiO₂).

Congelifraction

See frost wedging.

Conglomerate

A clastic rock composed of a fine matrix and rounded class. This is in contrast to a breccia.

Dunham Classification

A classification of limestone based on depositional textures. The classification consists of mudstone (90% mud), wackestone (>10% grains, mud supported), packstone (grain supported, but contains mud), grainstone (grain supported, no mud) and boundstone (g...More

Flint

Microcrystalline quartz (SiO₂) found in chalk. Chert is the equivalent in any other rock, i.e. flint is chert.

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