Presentation on theme: "Sedimentary rocks - lithification"— Presentation transcript:
1 Sedimentary rocks - lithification Sedimentary rocks are formed through lithification. Shown in (A) are unconsolidated particles. When subjected to lithification, they become sedimentary rock shown in (B).
2 Classification of sedimentary rocks DetritalChemicalSedimentary rocks are primarily grouped into two main types according to how they were formed. Detrital sedimentary rocks were formed through physical means (pressure) while chemical sedimentary rocks were chemically formed.
3 Detrital sedimentary rocks – fissility Fissility refers to the property of detrital sedimentary rocks that enables them to be split into thin sheets.home
4 Detrital sedimentary rocks – sorting The particles that make up detrital sedimentary rocks undergo sorting. Rocks upstream tend to be angular and poorly sorted while rocks downstream are rounded and well sorted.home
5 Very fine (less than 1/256 mm) Classification of sedimentary rocksSedimentary rocksDetritalCoarse (>2mm)Medium (1/16 to 2mm)Fine (1/16 to 1/256mm)Very fine (less than 1/256 mm)ChemicalDetrital rocks are classified according to the size of their particles.home
6 Classification of sedimentary rocks homeCoarse (>2mm)GravelConglomerate (Rounded particles)Breccia (Angular particles)Medium (1/16 to 2mm)SandQuartz sandstone (little feldspar)Arkose (abundant feldspar)Fine (1/16 to 1/256mm)MudSiltstoneVery fine (less than 1/256 mm)Shale
7 Classification of sedimentary rocks DetritalChemicalCalcite, CaCO3Quartz,SiO2Gypsum, CaSO4Halite, NaClPlant fragmentsChemical sedimentary rocks are classified according to their predominant component.home
8 Classification of sedimentary rocks Calcite, CaCO3Inorganic limestoneNonclastic: fine to coarse crystallineCrystalline limestoneTravertineBiochemical limestoneClastic: visible shell fragments loosely cementedCoquinaClastic: various size coral fragments cemented with calciteFossiliferous limestoneClastic: Microscopic shells and clayChalkCalcite rocks are grouped according to how they were formed (inorganic or via biochemical processes). Inorganic limestones are described as nonclastic which means that they are not made of particles. Biochemical limestones on the other hand, are made of particles and so are clastic.home
9 Classification of sedimentary rocks Quartz, SiO2Nonclastic: very fine crystalline(light colored)Chert(dark colored)FlintGypsum, CaSO4Nonclastic: fine to coarse crystallineRock gypsumHalite, NaClNonclastic: Fine to coarse crystallineRock SaltPlant fragmentsNonclastic: Fine-grained organic matterBituminous coalSedimentary rocks, environments and structures
10 Conglomerate (detrital, gravel, rounded particles) home
11 Breccia (detrital, gravel, angular particles) home
12 Quartz sandstone (detrital, sand, mostly quartz) home
24 Rock salt (chemical, nonclastic, NaCl, evaporite) home
25 Rock salt (chemical, nonclastic, NaCl, evaporite) Halites are known as evaporites because they are formed through the evaporation of water from chemically-concentrated solutions.home
26 Coal (chemical, nonclastic, plant remains) homeCoal exists in many forms. The first form is peat which is still impure and damp (and hence contains a low amount of stored energy). Peat that has undergone burial and pressure becomes lignite or bituminous coal (which is now more concentrated and hence has more energy). Anthracite is the metamorphic form of coal which is formed after intense pressure and heat.