sedimentaryrock

Sedimentary rock is a type of rock formed by the accumulation, compaction, and cementation of sediment or by the precipitation of minerals from water. Most sedimentary rocks form at or near the Earth’s surface and record past environments in layered deposits. They are commonly classified by their mode of origin into clastic, chemical, and biochemical (organic) groups.

Sedimentary rocks originate from weathering and erosion of preexisting rocks, transport of fragments by water, wind, or ice, and deposition in layers. Over time these layers are buried and undergo diagenesis, including compaction and cementation, which consolidate loose sediment into solid rock. Diagenetic minerals such as quartz, calcite, or hematite can cement grains together.

Clastic or detrital rocks are built from fragments of other rocks, with grain sizes ranging from clay to boulders; common examples include shale, siltstone, sandstone, conglomerate, and breccia. Chemical rocks form by precipitation of minerals from solution, including rock salt (halite), gypsum, and chert. Biochemical or organic rocks originate from accumulated biological material, such as limestone formed from skeletal carbonate, coal formed from plant material, and some cherts from microfossils.

Sedimentary rocks often preserve fossils and show layering or bedding, as well as features such as cross-bedding, ripple marks, and mud cracks that reflect depositional environments like rivers, deserts, lakes, and oceans. They are important as aquifers and hydrocarbon reservoirs and are widely used as building stone and in various industrial applications.