Sedimentary

Sedimentary is an adjective describing rocks or processes related to sedimentation. Sedimentary rocks form at or near the Earth’s surface through the accumulation and compaction of sediments, or through precipitation from water or biological activity. The process begins with weathering and erosion producing loose material that is transported by water, wind, ice, or gravity, then deposited when the energy of the transporting medium decreases. Over time, buried sediments are compacted and cemented by mineral deposits to become solid rock, a process known as lithification. Diagenesis continues after lithification, altering the rock at relatively low temperatures and pressures.

Sedimentary rocks are commonly categorized into clastic (detrital), chemical (inorganic precipitates), and biochemical or organic (from biological material) groups. Clastic examples include sandstone, siltstone, and shale. Chemical examples include limestone (from calcium carbonate precipitates in water) and rock salt. Biochemical examples include coal and some limestones formed from shells or corals.

They form in a wide range of environments, such as rivers, lakes, deserts (aeolian dunes), deltas, continental shelves, and deep-sea basins. Sedimentary rocks often display bedding and other structures (ripple marks, cross-bedding, mud cracks) that record past conditions. They are also important as archives of Earth history and hosts for fossils, as well as resources for groundwater, hydrocarbons, and minerals.