Sedimentary rocks are rocks that are commonly formed by erosion, transport, and depositing alluvium brought by the flowing water. Such rocks can be in the form of unbound granules (sands) or massive formation (sandstone). A characteristic feature of the sediments is the layered structure, a layer forming in a relatively short time on the surface of the Earth. NASA found sandstone layers on Mars.
Sedimentary rocks are the only rocks that can contain fossils. Unlike magmatic and metamorphic rocks, they do not form in the presence of high temperatures and pressures. Sedimentary rocks are created by the action of external agents that act on the surface of the Earth as the hydrosphere, atmosphere, and biosphere process called erosion.
Milieu (environmental factors) and Facies (rock characteristics) are specific to each sedimentary rock formation region. The diagenesis process is what leads to the conversion of sediments into sedimentary rocks often by adding binder (cementation material) of various types. It is made from clay minerals (phyllosilicates), carbonates (CaCO3), amorphous silica (SiO2), and oxy/oxyhydroxides of Fe (FeO (OH)).
More about the sandstone layers on Mars
Chemical sedimentary rocks arise from the precipitation of saturated evaporite-containing marine solutions (carbonates, sulfates, halides, etc.). Sedimentary rocks of biotic (biogenic) or Biolite origin are formed by the activity of living or dead organisms, for example, peat or lower coal from carbonized plant debris.
Residual sediments or residual rocks are formed from rocks decomposed by chemical factors in the atmosphere; examples of sedimentary rocks are laterite (on account of rocks containing iron) bauxite (limestone) and kaolin (on account of granite feldspars, rhyolite, arches). Sedimentary stones are essential as building materials (limestone and dolomite).
Also, these are the host rocks for fossil fuel resources, constituting an energy resource for crude oil and natural gas, the upper coal: anthracite and brown coal. Limestone rocks contain considerable quantities of carbon dioxide, an amount that has been fixed in geological times in the atmosphere, which is one of the explanations of the low CO2 content of the Earth’s atmosphere, compared to the neighboring planets Mars and Venus.