Siltstone

Siltstone is a clastic sedimentary rock composed mainly of silt-sized mineral grains. Its grains are finer than those of sandstone and coarser than those of claystone.

Silt: Silt is sediment made of mineral particles between sand and clay in size. Siltstone is defined by its dominant grain size: silt.
Sedimentation: Sedimentation is the settling and accumulation of particles carried by a fluid or gravity. Silt settles when transporting flows lose enough energy to carry it.
Sandstone: Sandstone is a clastic sedimentary rock composed mainly of sand-sized grains. Its grains are larger than siltstone's, making the boundary a grain-size distinction.
Sedimentary facies: A sedimentary facies is a body of rock whose features record a particular depositional environment. Siltstone layers help identify the environments in which fine sediment accumulated.
Grain size: Grain size is the diameter of particles in a sediment or sedimentary rock. It separates siltstone from sandstone and claystone.
Turbidity current: A turbidity current is a sediment-laden underwater flow driven downslope by gravity. Its deposits can include fine-grained layers containing siltstone.
Claystone: Claystone is a fine-grained clastic sedimentary rock dominated by clay-sized particles. Its particles are finer than siltstone's.
Stratigraphy: Stratigraphy is the study of rock layers, their sequence, and their relationships through time. Siltstone beds provide layers that can be compared and traced within sedimentary sequences.
Clastic sedimentary rock: A clastic sedimentary rock forms when fragments of older rocks accumulate and become cemented. Siltstone belongs to this rock family because it consists of sediment grains.
Compaction (geology): Compaction is the compression of sediment as overlying material reduces its pore space. Burial pressure packs silt grains together during siltstone formation.

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