Sedimentary rocks - lithification Sedimentary rocks are formed through lithification. Shown in (A) are unconsolidated particles. When subjected to lithification, they become sedimentary rock shown in (B).

Classification of sedimentary rocks Detrital Chemical Sedimentary rocks are primarily grouped into two main types according to how they were formed. Detrital sedimentary rocks were formed through physical means (pressure) while chemical sedimentary rocks were chemically formed.

Detrital sedimentary rocks – fissility Fissility refers to the property of detrital sedimentary rocks that enables them to be split into thin sheets. home

Detrital sedimentary rocks – sorting The particles that make up detrital sedimentary rocks undergo sorting. Rocks upstream tend to be angular and poorly sorted while rocks downstream are rounded and well sorted. home

Very fine (less than 1/256 mm) Classification of sedimentary rocks Sedimentary rocks Detrital Coarse (>2mm) Medium (1/16 to 2mm) Fine (1/16 to 1/256mm) Very fine (less than 1/256 mm) Chemical Detrital rocks are classified according to the size of their particles. home

Classification of sedimentary rocks home Coarse (>2mm) Gravel Conglomerate (Rounded particles) Breccia (Angular particles) Medium (1/16 to 2mm) Sand Quartz sandstone (little feldspar) Arkose (abundant feldspar) Fine (1/16 to 1/256mm) Mud Siltstone Very fine (less than 1/256 mm) Shale

Classification of sedimentary rocks Detrital Chemical Calcite, CaCO3 Quartz, SiO2 Gypsum, CaSO4 Halite, NaCl Plant fragments Chemical sedimentary rocks are classified according to their predominant component. home

Classification of sedimentary rocks Calcite, CaCO3 Inorganic limestone Nonclastic: fine to coarse crystalline Crystalline limestone Travertine Biochemical limestone Clastic: visible shell fragments loosely cemented Coquina Clastic: various size coral fragments cemented with calcite Fossiliferous limestone Clastic: Microscopic shells and clay Chalk Calcite rocks are grouped according to how they were formed (inorganic or via biochemical processes). Inorganic limestones are described as nonclastic which means that they are not made of particles. Biochemical limestones on the other hand, are made of particles and so are clastic. home

Classification of sedimentary rocks Quartz, SiO2 Nonclastic: very fine crystalline (light colored) Chert (dark colored) Flint Gypsum, CaSO4 Nonclastic: fine to coarse crystalline Rock gypsum Halite, NaCl Nonclastic: Fine to coarse crystalline Rock Salt Plant fragments Nonclastic: Fine-grained organic matter Bituminous coal Sedimentary rocks, environments and structures

Conglomerate (detrital, gravel, rounded particles) home

Breccia (detrital, gravel, angular particles) home

Quartz sandstone (detrital, sand, mostly quartz) home

Arkose (detrital, sand, abundant felspar) home

Siltstone (detrital, fine-sized particles, mud) home

Shale (detrital, very fine particles, mud, may contain fossils) home

Crystalline limestone (chemical, nonclastic, fine to coarse crystalline) home

Travertine (chemical, nonclastic, fine to coarse, cavewaters) home

Coquina (chemical, clastic, shell fragments, loosely cemented) home

Fossiliferous limestone (chemical, clastic, coral fragments, calcite cement) Fossiliferous limestone are made of coral reef fragments cemented strongly by calcite. home

Chalk (chemical, clastic, microscopic shells and clay) home

Chert (chemical, nonclastic, quartz, light colored) home

Flint (chemical, nonclastic, quartz, dark colored) home

Rock gypsum (chemical, nonclastic, CaSO4) home

Rock salt (chemical, nonclastic, NaCl, evaporite) home

Rock salt (chemical, nonclastic, NaCl, evaporite) Halites are known as evaporites because they are formed through the evaporation of water from chemically-concentrated solutions. home

Coal (chemical, nonclastic, plant remains) home Coal exists in many forms. The first form is peat which is still impure and damp (and hence contains a low amount of stored energy). Peat that has undergone burial and pressure becomes lignite or bituminous coal (which is now more concentrated and hence has more energy). Anthracite is the metamorphic form of coal which is formed after intense pressure and heat.

Peat home

Lignite or bituminous coal home

Bituminous coal can be metamorphosed into anthracite home