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The lithologic types. Sedimentary rocks
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The lithologic types. Sedimentary rocks
The sedimentary rocks are those formed by the accumulation of materials or particles, by chemical precipitation or by
the growth of organisms, subaerial, under sea or lake-water conditions: the sediments. Generally these are deposited
in horizontal layers: the strata. As they are buried, the sediments that are not yet consolidated are compacted by the
weight of the overlying deposits and they transform into rocks by cementation. This process is called lithification. The
cementation takes place by the precipitation of the minerals dissolved in the fluids that occupy the gaps between the
particles, joining them. The sediments often contain remains of organisms, which will become fossils inside the
sedimentary rocks.
The sedimentary rocks are classified bearing in mind the process that originated them and their composition. The main
groups are the detrital, the carbonatic and the evaporitic rocks.
The detrital rocks are formed by the transport, accumulation and cementation of solid particles derived from the
disintegration and weathering of pre-existing rocks. They are classified by the size and morphology of the grains. The
most common are, going from large to small grain size, the conglomerates and the breccias, sandstones, siltstones
and mudrocks; the lutites are formed by clays and silt. Other classification criteria are the composition of the particles,
and the texture or the type of cement.
The rocks formed by chemical precipitation are the result of the crystallization of chemical elements that are dissolved
in the sea and in the lakes. They are classified according to their mineralogical composition. The most relevant groups
are the evaporites, salts and gypsum, and the carbonates. The latter, have their own classification in which
preference is given to the mineral composition (calcite, dolomite) and mainly to the textures of these rocks, especially
to the grain size and the type of components they are composed of.
The rocks formed by the growth of organisms are mostly carbonates. It is necessary to differentiate the bioconstructions of reefs from those in which the carbonate is in the form of mud, of grains and particles or of skelletal
components. The latter have characteristics in common with the detrital rocks and are quite often associated.
The classification is not strict, since there are numerous rocks or lithological associations that are the result of the
intersection of two or all these types.
Detrital rocks of mixed composition (D)
Dg-Mx: Polymictic conglomerates
Dg-Mx: Polymictic conglomerates
Dg-Mx: Polymictic breccia
Dg-Mx: Polymictic breccia
Dh-Mx: Conglomerates, sandstone and mudrocks
Dh-Mx: Conglomerates, sandstone and mudrocks
Dm-Mx: Large-grained sandstone
Dm-Mx: Large-grained sandstone
Dm-Mx: Fine-grained sandstone
Dm-Mx: Fine-grained sandstone
Df-Mx: Sandstone and mudrocks
Df-Mx: Sandstone and mudrocks
Detrital rocks of siliceous composition (D)
Dg-Q/Si: Conglomerates of quartz pebbles
Dg-Q/Si: Conglomerates of quartz pebbles
Dh-Q/Si: Sandstones and conglomerates
Dh-Q/Si: Sandstones and conglomerates
Dh-Q/Si: Sandstone and mudrocks
Dh-Q/Si: Sandstone and mudrocks
Dm-Q/Si: Arkoses
Dm-Q/Si: Arkoses
Df-Q/Si: Red lutites
Df-Q/Si: Red lutites
Df-Q/Si: Slates
Df-Q/Si: Slates
Non consolidated detrital sediments of mixed composition (DNc)
DhNc-Mx: Gravels and pebbles
DhNc-Mx: Gravels and pebbles
DhNc-Mx: Gravels and mud
DhNc-Mx: Gravels and mud
DhNc-Mx: Sands
DhNc-Mx: Sands
DhNc-Mx: Beach sand
DhNc-Mx: Beach sand
DhNc-Mx: Sand and silt
DhNc-Mx: Sand and silt
DhNc-Mx: Colluvium
DhNc-Mx: Colluvium
Detrital rocks with organic matter (DO)
Mx/Mo: Black slates
Mx/Mo: Black slates
Mx/Mo: Fine-grained sandstone with organic matter
Mx/Mo: Fine-grained sandstone with organic matter
Mx/Mo: Peat
Mx/Mo: Peat
Carbonate rocks (C)
C-Ca: Mudstone, fine-grained limestone
C-Ca: Mudstone, fine-grained limestone
C-Ca: Grainstone, large-grained limestone
C-Ca: Grainstone, large-grained limestone
C-Ca: Reef, reef limestone
C-Ca: Reef, reef limestone
C-Do: Dolomite
C-Do: Dolomite
C-Ca/Do: Limestone and dolomite
C-Ca/Do: Limestone and dolomite
CDh-Ca/Mx: Travertine
CDh-Ca/Mx: Travertine
Carbonate and detrital rocks (CD)
CDg-Ca/Si: Carbonate breccia
CDg-Ca/Si: Carbonate breccia
CDg-Ca/Si: Bioclastic grainstone
CDg-Ca/Si: Bioclastic grainstone
CDf-Ca/Si: Marly limestone
CDf-Ca/Si: Marly limestone
Detrital and carbonated rocks (DC)
DfC-Si/Ca: Marls
DfC-Si/Ca: Marls
CDf-Ca/Si: Limestones and mudrocks
CDf-Ca/Si: Limestones and mudrocks
DhC-Mx/Ca: Mudrocks, marls, sandstones and limestones
DhC-Mx/Ca: Mudrocks, marls, sandstones and limestones
Carbonate rocks with organic matter (CO)
CO-CaMo: Limestone and lignite
CO-CaMo: Limestone and lignite
CO-CaMo: Limestone with coal
CO-CaMo: Limestone with coal
CO-CaMo: Bituminous marl with oil
CO-CaMo: Bituminous marl with oil
Detrital rocks, carbonated and evaporítiques (DE, DCE)
DE: Mudrocks and gypsum
DE: Mudrocks and gypsum
DCE: Mudrocks, sandstones, limestones, marls and gypsum
DCE: Mudrocks, sandstones, limestones, marls and gypsum
DCE: Marls and gypsum
DCE: Marls and gypsum
Evaporites (E)
E: Salt
E: Salt
E: Sodium and potassium salts
E: Sodium and potassium salts
E: Gypsum
E: Gypsum
Other sedimentary rocks
Argiles Clays with carbonate concretions
Clays with carbonate concretions
Lidytes
Lidytes
Bauxite
Bauxite
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