sedimentarie

Sedimentary rocks, commonly referred to as sedimentaries, are rocks formed by the accumulation and lithification of sediments derived from preexisting rocks, biological material, or chemical precipitation. Most originate at or near the Earth’s surface through weathering, erosion, transport by water, wind, or ice, and subsequent deposition in layers. Over time, burial increases pressure and temperature enough to compact the grains and cement minerals such as quartz, calcite, or iron oxides, forming solid rock.

Classification is traditionally into clastic (detrital) rocks such as sandstone, siltstone, shale, and conglomerate; chemical rocks such as evaporites (halite, gypsum) and precipitates (soda-rich or carbonate minerals); and biochemical or organic rocks such as coal and certain limestones formed from accumulated shells or other organic matter.

Features commonly observed in sedimentary rocks include bedding or stratification, cross-bedding, ripple marks, mud cracks, and fossils. These features help interpretation of past environments of deposition, including rivers, deltas, deserts, beaches, reefs, and deep-sea basins.

Physically, sedimentary rocks are important for porosity and permeability, influencing groundwater flow and hydrocarbon storage. They host most fossil records and are economically significant as sources of energy, building materials, and minerals.

Relation to other rock types: unlike igneous and metamorphic rocks, sedimentaries form at low temperatures and pressures near the surface and preserve evidence of Earth’s surface processes and environments. They cover substantial portions of the continental crust and provide crucial insights into geologic history.