Sedimentary Rocks: Formation & Classification PDF

PETROLOGY Origin of Sedimentary Rocks Origin of Sedimentary Rocks Sedimen...

PETROLOGY Origin of Sedimentary Rocks Origin of Sedimentary Rocks Sedimentary rocks are formed from deposits of pre- existing rocks or pieces of once-living organism that accumulate on the Earth's surface. If sediment is buried deeply, it becomes compacted and cemented, forming sedimentary rock. Sedimentary rocks are formed from deposits of pre-existing rocks or pieces of once-living organism that accumulate on the Earth's surface. If sediment is buried deeply, it becomes compacted and cemented, forming sedimentary rock. https://www.learner.org/wp-content/interactive/rockcycle/rockdiagram/ Rock Cycle of Sedimentary Rocks Karst limestone formation near the western coast of Madagascar Wind Water Chemicals Biological Activity Igneous Rocks Weathering Soil And Metamorphic Rocks Erosion Sedimentary Rocks Sediments COMPACTION Lithification TRANSPORTATION DEPOSITION CEMENTATION (Diagenesis) PRECIPITATION https://www.thoughtco.com/sedimentary-rock-types-4123132 Classifications of Sedimentary Rocks Classifications of Sedimentary Rocks Based on Mode of Formation Based on Mode of Formation Clastic Rocks (Detrital Rocks) Clastic Rocks (Detrital Rocks) - mechanically-formed rocks or terrigenous rocks - mechanically-formed rocks or terrigenous rocks Non-Clastic Rocks Terrigenous 1) Biologically or Organically-formed rocks - particles of rock derived from pre-existing rock through weathering and erosion. 2) Chemically-formed rocks Processes in the Stage 1: Stage 2: Stage 3: Stage 4: Formation of Weathering Transportation Deposition Lithification Clastic Rocks and Erosion of Sediments of Sediments (Diagenesis) https://geologyscience.com/category/rocks/sedimentary-rocks/non-clastic-sedimentary-rock/ https://geologyscience.com/category/rocks/sedimentary-rocks/non-clastic-sedimentary-rock/ Processes in the Formation of Clastic Rocks Examples of Weathering and Erosion Stage 1: Weathering and Erosion Factors: Temperature First Step: Humidity Weathering is a process that breaks down pre- Water https://www.thoughtco.com/sedimentary-rock-classification-diagrams-4123127 existing rocks into smaller fragments, grains and Wind particles (sediments or detritus). Glacier Many others Second Step: Erosion is a mechanical process, usually driven by water, wind, gravity, or ice, which transports sediments from the place of weathering. The disintegrated pre-existing rocks thus form a layer of loose, decayed rock debris, or soil, which accumulates near the source. Examples of Weathering and Erosion Examples of Weathering and Erosion https://3.bp.blogspot.com/-MLrmi330RBk/ULWBkJj11SI/AAAAAAAAAn0/qz96FRPz-Kw/s1600/P1080091.JPG https://www.toppr.com/ask/content/story/amp/physical-weathering-124093/  Sediment particle size Processes in the Formation of Clastic Rocks Stage 2: Transportation of Sediments Transportation is the process by which sediments can be moved by sliding down slopes, being picked up by the wind, or by being carried by running water in streams, rivers, or ocean currents. https://www2.tulane.edu/~sanelson/eens1110/sedrx.htm Agents of Sediment Transport Water https://earthsurface.readthedocs.io/en/latest/sedtransport.html Wind Ice/Glacier Gravity Biological Agents Transportation by WATER The amount of sediment transported by water depends on Examples of Sediment Transport by Water the velocity and turbulence of the water, the size and shape of the sediment particles, and the availability of sediment. https://www.nps.gov/articles/coastal-processes-sediment-transport-and-deposition.htm Movement by rolling, sliding, or dragging is called traction. Saltation is a series of short leaps or bounces off the bottom. https://worldrivers.net/2020/03/31/sediment-transport/ Examples of Sediment Transport by Water Examples of Sediment Transport by Water https://www.nps.gov/articles/coastal-processes-sediment-transport-and-deposition.htm https://www.hydrosedi.net/sediment-transport Transportation by WIND Wind can move both fine-grained and coarse-grained Examples of Sediment Transport by Wind sediment, and the amount of sediment transported depends on the wind speed and the size of the sediment particles. https://www.agric.wa.gov.au/fire/wind-erosion-control-after-fire-western-australia sliding Movement by rolling, sliding, or dragging is called traction. Saltation is a series of short leaps or bounces off the bottom. https://worldrivers.net/2020/03/31/sediment-transport/ Examples of Sediment Transport by Wind Transportation by ICE/GLACIER Sediment can be transported by glaciers, which move slowly downhill under their own weight. Glaciers can transport large amounts of sediment, including boulders, cobbles, and sand. Supraglacial (on top of the ice) and englacial (within the ice) sediments that slide off the melting front of a stationary glacier can form a ridge of unsorted sediments called an end moraine. The end moraine that represents the farthest advance of the glacier is a terminal moraine. Sediments transported and deposited by glacial ice are known as till. https://www.youtube.com/watch?v=wAEi9s9bEpY https://opentextbc.ca/geology/chapter/16-4-glacial-deposition/ Examples of Sediment Transport by Ice Examples of Sediment Transport by Ice https://geologylearn.blogspot.com/2015/07/continental-glacier-deposition.html https://www.internetgeography.net/topics/how-do-glaciers-transport-material/ Transportation by Gravity Examples of Sediment Transport by Gravity Sediment can be transported by gravity, especially on steep slopes and in mountainous regions. Gravity can cause landslides, rockfalls, and debris flows that transport sediment downslope. Peru https://www.mdpi.com/2073-4441/12/10/2907 https://en.wikipedia.org/wiki/Landslide 2018 Examples of Sediment Transport by Gravity Examples of Sediment Transport by Gravity Peru https://www.reuters.com/world/europe/swiss-prepare-evacuate-village-threatened-by-vast-landslide-2023-05-11/ https://www.linkedin.com/pulse/causes-effects-landslide-abid-jahan/ 2018 Examples of Sediment Transport by Gravity Examples of Sediment Transport by Gravity https://www.reuters.com/world/europe/swiss-prepare-evacuate-village-threatened-by-vast-landslide-2023-05-11/ https://www.cdph.ca.gov/Programs/EPO/Pages/BI_Natural-Disasters_Landslides-and-Mudslides.aspx Transportation by Biological Agents Examples of Sediment Transport by Biological Agents Sediment can also be transported by living organisms, such as burrowing animals, root systems of plants, and microbes. https://www.mdpi.com/2073-4441/12/10/2907 https://www.bgs.ac.uk/wp-content/uploads/2020/03/P006493.jpg Examples of Sediment Transport by Biological Agents Examples of Sediment Transport by Biological Agents https://www.jkgeography.com/fluvial-processes-weathering-and-mass-movement.html https://teleskola.mt/weathering-of-rocks/ Processes in the Formation of Clastic Rocks Processes in the Formation of Clastic Rocks Stage 3: Deposition of Sediments Stage 3: Deposition of Sediments Depositional Environment Deposition is the laying down of sediment Depositional environments are the locations and conditions where sediment carried by wind, water, or ice. Sediment can be accumulates and are determined by the physical, chemical, and biological transported as pebbles, sand & mud, or as salts processes at work. They are classified based on the characteristics of the dissolved in water. Salts may later be deposited sediment and the dominant processes that create the deposit. by organic activity (e.g. as sea-shells) or by https://geologyscience.com/geology-branches/sedimentology/sediment-transport-and-deposition/?amp evaporation. https://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3463.html  Processes in the Formation of Clastic Rocks Examples of Alluvial Deposits Stage 3: Deposition of Sediments Depositional Environment TYPE OF SEDIMENT DEPOSIT DESCRIPTION Deposits formed by flowing water in river Alluvial Deposits channels, floodplains, and alluvial fans. https://www.thescienceofrivers.com/topics/what-is-an-alluvial-river https://geologyscience.com/geology-branches/sedimentology/sediment-transport-and-deposition/?amp Examples of Alluvial Deposits Examples of Alluvial Deposits A floodplain is a generally flat area of land next to a river or stream. An alluvial fan is a triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt. This sediment is called alluvium. Alluvial fans are usually created as flowing water interacts with mountains, hills, or the steep walls of canyons. https://en.wikipedia.org/wiki/Floodplain https://pediaa.com/what-is-the-difference-between-alluvial-fan-and-delta/ Examples of Alluvial Deposits Processes in the Formation of Clastic Rocks Stage 3: Deposition of Sediments Depositional Environment TYPE OF SEDIMENT DEPOSIT DESCRIPTION Accumulation of sediment at the mouth of a river as it enters a standing body of water, often Deltaic Deposits forming branching patterns of channels and distributaries. https://geo.libretexts.org/Courses/University_of_California_Davis/GEL_109%3A_Sediments_and_Strata_%28Sumner%29/Textbook_Construction/Alluvial_fans https://geologyscience.com/geology-branches/sedimentology/sediment-transport-and-deposition/?amp Examples of Deltaic Deposits Processes in the Formation of Clastic Rocks Delta is the flat, low-lying plain that sometimes forms at the mouth of a river from Stage 3: Deposition of Sediments deposits of sediments. Depositional Environment TYPE OF SEDIMENT DEPOSITS DESCRIPTION Deposits formed along the coast by the action Coastal Deposits of waves, currents, and tides, including beaches, barrier islands, and lagoons. https://opentextbc.ca/geology/chapter/13-4-stream-types/ https://geologyscience.com/geology-branches/sedimentology/sediment-transport-and-deposition/?amp Examples of Coastal Deposits Examples of Coastal Deposits A beach is a landform along the coast of an ocean or sea. https://pilebuck.com/wp-content/uploads/2014/04/shutterstock_433644076.jpg https://education.nationalgeographic.org/resource/beach/ Examples of Coastal Deposits Examples of Coastal Deposits A lagoon is a body of water separated from larger bodies of water by a natural barrier. A barrier island is a constantly changing deposit of sand that forms parallel to the coast. https://oceanservice.noaa.gov/facts/barrier-islands.html https://www.worldatlas.com/articles/what-is-a-lagoon-how-many-types-are-there.html Examples of Coastal Deposits Examples of Coastal Deposits A barrier island is a constantly changing deposit of sand that forms parallel to the coast. https://worldlandforms.com/landforms/wp-content/uploads/2015/03/continental-shelf.jpg https://science.howstuffworks.com/environmental/conservation/issues/barrier-island.htm Processes in the Formation of Clastic Rocks Examples of Marine Deposits Stage 3: Deposition of Sediments https://iilss.net/what-is-the-meaning-of-continental-slope-in-law-of-the-sea-losc-and-customary-international-law/ Depositional Environment TYPE OF SEDIMENT DEPOSITS DESCRIPTION edge of a continent that Deposits formed in the ocean by currents, lies under the ocean. waves, and other processes, including Marine Deposits continental shelves, slopes, and deep-sea slope between the outer edge basins. This includes parts of the oceans where deep water prevails. of the continental shelf and the deep ocean floor https://geologyscience.com/geology-branches/sedimentology/sediment-transport-and-deposition/?amp Processes in the Formation of Clastic Rocks Examples of Glacial Deposits Stage 3: Deposition of Sediments Depositional Environment TYPE OF SEDIMENT DEPOSITS DESCRIPTION Deposits formed by glaciers, including Glacial Deposits moraines, till, and glacial outwash plains. A moraine is material left behind by a moving glacier. This material is usually soil and rock. https://geologyscience.com/geology-branches/sedimentology/sediment-transport-and-deposition/?amp https://www.antarcticglaciers.org/glacial-geology/glacial-landforms/glacial-depositional-landforms/moraine-formation/ Examples of Glacial Deposits Processes in the Formation of Clastic Rocks Glacial till is the collective term for all the material carried by the body of the Stage 3: Deposition of Sediments ice as it flows over land, while glacial outwash is restricted to the particles carried by the water arising from the melting of glacier ice. Depositional Environment TYPE OF SEDIMENT DEPOSITS DESCRIPTION Deposits formed by wind, including sand dunes Aeolian Deposits and loess. https://opentextbc.ca/geology/chapter/16-4-glacial-deposition/ https://geologyscience.com/geology-branches/sedimentology/sediment-transport-and-deposition/?amp Examples of Aeolian Deposits Sand dunes form when the wind deposits sand. Examples of Aeolian Deposits Loess form when the wind deposits clay and silt. https://www.smithsonianmag.com/smart-news/sand-dunes-communicate-they-migrate-180974138/ https://blogs.egu.eu/divisions/cl/2020/09/25/desertloess/ Processes in the Formation of Clastic Rocks Examples of Lacustrine Deposits Stage 3: Deposition of Sediments Depositional Environment TYPE OF SEDIMENT DEPOSITS DESCRIPTION Lacustrine Deposits formed in lakes, including deltas, and Deposits deep lake basins. https://smartwatermagazine.com/news/duke-university/lake-sediments-show-decades-coal-ash-contamination https://geologyscience.com/geology-branches/sedimentology/sediment-transport-and-deposition/?amp Examples of Lacustrine Deposits Processes in the Formation of Clastic Rocks Stage 4: Lithification (Diagenesis) Lithification, also known as diagenesis or consolidation is the process of transformation of deposited loose sediments to solid cohesive rock masses. It is also known as lithification or https://rwu.pressbooks.pub/app/uploads/sites/7/2017/01/figure13.4.1.jpg sometimes consolidation. Stage 3: Stage 1: Stage 2: Formation of Stages of Lithification Compaction Sedimentation Sedimentary Rock https://www2.tulane.edu/~sanelson/eens1110/sedrx.htm Main Types of Clastic Rocks TYPE Texture Grain size OTHER CHARACTERISTICS Grains loosely packed. Conglomerate and Conglomerate Well-rounded clasts Spaces between grains are Coarse 2 mm and larger Breccia Breccia Angular clasts filled by water. Grains are compacted to fit together more tightly. Sandstone Arenite Clean sandstone Water is squeezed out from Medium 63 μm – 2 mm spaces between grains. Wacke Dirty sandstone Grains are squeezed tightly together and may begin to Mudrocks Shale With laminations and breaks into sheets dissolve where contacts are Siltstone Dominated by silt under high pressure. Fine Less than 63 μm Solutions between grains Cementing materials Mudstone Mix of silt and clay precipitate minerals that ▪ Silica cement (Silica) Claystone Dominated by clay cement grains together to ▪ Calcite cement (Calcium carbonate) form a rock ▪ Hematite or Limonite cement (Iron oxide) https://www.facebook.com/Geologistspage/photos/a.513662172419756/610561679396471/ https://opentextbc.ca/physicalgeologyh5p/chapter/clastic-sedimentary-rocks/ Examples of Conglomerate Rocks Examples of Breccia Rocks https://nagra.ch/en/knowledge-centre/rocks/ https://geologyscience.com/rocks/sedimentary-rocks/conglomerate/ https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/conglomerate.html https://www.dreamstime.com/natural-sample-conglomerate-sedimentary-rock-composed-cemented-gravel-pebbles-white-background-specimen-rounded-image106056750 https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/breccia.html https://www.alexstrekeisen.it/english/sedi/breccia.php  Examples of Sandstone Examples of Mudrocks Greywacke Mudstone Claystone Siltstone Lithic Arenite Ferruginous Sandstone Arkose Shale Marlstone Quartz Arenite Calcareous sandstone https://www.geologyin.com/2023/12/sandstone-sedimentary-rock.html https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/mudstone.html https://www.thoughtco.com/shale-rock-4165848 https://www.geologysuperstore.com/product/marl-red/ Factors Affecting the Diagenesis of Sedimentary Rocks Types of Diagenesis of Sedimentary Rocks FACTOR EFFECT TYPE DESCRIPTION Temperature Diagenesis is affected by temperature, as higher temperatures can cause Compaction As sediment is buried, the weight of overlying layers causes grains to become minerals to recrystallize and change in mineralogy. compressed and close together, reducing the volume of pore space between Pressure Pressure can also play a role in diagenesis, as increased pressure can cause them. compaction and cementation of sedimentary particles. Cementation As pore space is reduced, mineral-rich fluids may flow through the rock, Fluids The fluids present in sedimentary rocks can also influence diagenesis. depositing minerals that bind grains together. Common cements include calcite, quartz, and clay minerals. https://geologyscience.com/geology-branches/sedimentology/diagenesis-of-sedimentary-rocks/?amp https://geologyscience.com/geology-branches/sedimentology/diagenesis-of-sedimentary-rocks/?amp Groundwater, for example, can alter the mineralogy of sedimentary rocks through dissolution and precipitation. Recrystallization Under conditions of elevated temperature and pressure, minerals in the rock Time The longer sedimentary rocks are buried, the more time there is for diagenesis may dissolve and re-precipitate as larger, more stable crystals. to occur. Replacement In some cases, minerals in the original sediment are replaced by new Composition of The composition of the sedimentary rock can also affect diagenesis, as some minerals. For example, aragonite shells may dissolve and be replaced by the sediment minerals are more susceptible to alteration than others. calcite. Climate The climate in which sedimentary rocks are deposited can also affect Dissolution Some minerals may dissolve during diagenesis, leaving behind pores or vugs. diagenesis. For example, arid climates can lead to the formation of evaporites, Organic Bacterial activity can produce methane, which can cause carbonate minerals while humid climates can lead to the formation of kaolinite. processes to precipitate. Classifications of Sedimentary Rocks Organic Sedimentary Rock Based on Mode of Formation These rocks are formed in-situ with existence of suitable environmental Non-Clastic Rocks condition including oxidation and reduction condition. Oxidation occurs in a chemical reaction when there is a loss of electrons and a gain of Oxygen. - formed from chemical or organic processes rather than the accumulation On the other hand, reduction happens in a reaction when there is a gain of electrons and a loss of Oxygen. of rock fragments Besides these conditions, temperature, pressure and time of burial are Type of Non-Clastic Rock Mode of Formation important for the formation of organic sedimentary rocks. https://geologyscience.com/geology-branches/sedimentology/diagenesis-of-sedimentary-rocks/?amp formed from the accumulation of any animal or Burial occurs when more sediments are piled onto existing sediments, and layers formed earlier are Organic Sedimentary Rock plant debris such as shells and bones covered and compacted. formed when the water components evaporate, Chemical Sedimentary Rock These rocks are characterized by non-clastic textures and structures because leaving dissolved minerals behind. the formation of these rocks occur in low energy condition. In a high energy environment, such as a river bed, currents are able to carry large particles. When the current loses energy, these will be deposited. Low energy currents cannot carry large particles, and so fine grained rocks form in a low energy environment. https://geologyscience.com/category/rocks/sedimentary-rocks/non-clastic-sedimentary-rock/  Examples of Organic Sedimentary Rocks Examples of Limestone Formation Bryozoan limestone (upper part) and chalk (lower) Denmark Fossiliferous limestone Diatomite Silurian limestone Grainstone Estonia Coal Coquina Chalk https://www.sandatlas.org/limestone/ https://zh.mindat.org/min-9353.html https://geologyscience.com/rocks/sedimentary-rocks/non-clastic-sedimentary-rock/diatomite/ https://www.mindat.org/gm/49207 https://www.sandatlas.org/limestone/ Chemical Sedimentary Rock Examples of Chemical Sedimentary Rocks When the concentration of ions such as Na+,Ca2+, and NCO3− exceeds the saturation point for water, a situation known as supersaturation occurs. During supersaturation, solutes will settle out of the water to produce chemical rocks. Chert Iron Ore Oxidation occurs in a chemical reaction when there is a loss of electrons and a gain of Oxygen. On the other hand, reduction happens in a reaction when there is a gain of electrons and a loss of Oxygen. https://geologyscience.com/geology-branches/sedimentology/diagenesis-of-sedimentary-rocks/?amp Rock Gypsum Rock Salt Dolostone https://www.sandatlas.org/limestone/ https://zh.mindat.org/min-9353.html https://geologyscience.com/rocks/sedimentary-rocks/non-clastic-sedimentary-rock/diatomite/ https://www.mindat.org/gm/49207 Stalactite and Stalagmite Examples of Sedimentary Rocks and Their Characteristics and Uses Stalactites hang from the ceiling of a cave while stalagmites grow from the cave floor. https://thestorytellers.com/the-story-cave-stalactites-and-stalagmites/ Sedimentary Rocks Sedimentary Rocks Conglomerate Breccia - sedimentary rocks of clastic nature and are classed as rudite - sedimentary rocks of clastic nature and are classed as rudite Uses On the basis of their source, commonly recognized breccias are Conglomerates with fi ne matrix textures are used for ornamental works in buildings, as follows: monuments, grave stones, and as tiles. However, their use is limited due to the irregular Basal Breccia grain sizes affecting durability. They act as reservoirs of groundwater, natural gas and petroleum. It is formed when fragments of chert and other similar rocks in the coastal regions are got cemented by the fine mud brought by the advancing seawater. Significance Fault Breccia When the sediment is first deposited, there are lots of open spaces or pores. Cement can affect the amount of pore space that is left in a rock as it solidifies. Also called crush-breccia, these are formed by the angular fragments produced while Conglomerates usually have significant pore space and they are generally a good rock to faulting, due to crushing effect of the block movements, and by their subsequent act as a reservoir for ground water, natural gas and petroleum. embedment in clay and other fi ne material. Agglomeratic Breccia It is formed from angular and sub-angular fragments derived from volcanic eruptions. Sedimentary Rocks Sedimentary Rocks Sandstone Shale - mechanically formed sedimentary rocks and belong to an arenaceous group. - fine-grained sedimentary rock that forms from the compaction of silt and clay-size Composition mineral particles, commonly called mud. Quartz (SiO2) is the most common mineral making the sandstones. Quartz, feldspar, mica, Composition garnet and magnetite may also occur in small proportions. The component grains may be Shale is a fine-grained, moderately to well sorted rock formed by the compaction of well cemented together by siliceous, calcareous, argillaceous or ferruginous in composition, or rounded silt- and clay-sized grains. Accessory minerals like oxides of iron, carbonates, by welding by natural pressures from overlying sediments. sulphide minerals and heavy mineral grains, and organic matter are also present. Silica and clay minerals together make more than 70% of shales in most cases. Uses Sandstones are very useful natural resources. Generally, sandstone is a very porous rock. It Uses is the ideal rock for groundwater and oil reservoirs. They are the biggest source for Shale is used to manufacture bricks and tiles. Cement is another important construction materials of construction like building stones, pavement stones, road aggregate and material that is often made with shale. These are sources of alumina, paraffin and oil. aggregate for making concrete. Mined sandstone can be cut, polished and carved for use as ornamental rocks for buildings, monuments, grave stones, tiles, etc. Sandstone can also provide silica for glass production. Some mineral ores are found in sandstone. Uranium minerals are associated with sandstone deposits. Heavy minerals such as rutile, gold, diamonds and others can be found in sandstones from prehistoric placed deposits. Sedimentary Rocks Sedimentary Rocks Mudstone Limestone - These are fine-grained clastic rocks with grains less than 1/16 mm in - Limestone is by far the most abundant chemically precipitated rock. It is composed diameter. Mudstones are formed from the compaction and cementation principally of calcium carbonate (CaCO3—dominantly calcite), with subordinate (lithification) of muddy sediments proportions of magnesium carbonate. Magnesium oxide is a common impurity in most limestones; when its percentage exceeds 2 per cent, the rock is called magnesian limestone. Limestones are formed both chemically and organically. Composition Pure limestone is invariably made up of mineral calcite (CaCO3). In the limestone rock formations, Siltstone however, presence of dolomite CaMg(CO3)2, quartz (SiO2), feldspar minerals and silicon dioxide, iron oxides or carbonates, and aluminum oxide is rather a common feature. - Clastic sedimentary rocks consisting of silt-sized particles are termed siltstones. The most common minerals in siltstones are quartz, clays and Texture chlorite. The most important textural feature of limestones is their fossiliferous nature. Fossils in all stages of preservation may be found in limestones. Other varieties of limestones show dense arid compact texture; some may be loosely packed and highly porous, others may be compact and homogeneous. Concretionary texture is also common in limestones. Uses Limestones are the primary source of lime for cements. Cement is considered one of the most important construction materials. It can be used as a building stone and road ballast, but is not quite as strong as sandstone. In metallurgical industries, it is used as a fl ux. Limestone is also used in chemical industries.  Sedimentary Rocks Sedimentary Rocks Limestone Dolostone Types - also called dolomite, is an evaporative sedimentary rock Chalk It is the purest form of limestone. It is porous, fine-grained and has an earthy texture and generally friable. Common colour of chalk is white. Some chalks may be exceptionally rich in the remains of foraminifera (very Composition small sea organisms). It is a carbonate rock composed of the mineral dolomite, a calcium-magnesium carbonate Shelly Limestone It has a rich assemblage of fully or partly preserved fossils. Shelly limestone is also called [CaMg(CO3)2]. Ferrous iron is present in small proportions in some of its varieties. It is fossiliferous limestone. Those limestones that are made up of fragments of sea shells only, are termed coquina. similar to limestone in general appearance, but reacts with acid only when powdered. Argillaceous Limestone These limestones are impure limestones containing clay as major constituent and are of Texture allochthonous origin. When the clay and calcium carbonates are present in almost equal proportions, the rock is Dolostone shows textures mostly similar to limestones. Some of its varieties are be coarsely known as marl. crystalline, finely crystalline or show interlocking crystals. Kankar It is a non-marine nodular or concretionary form of carbonate material formed by evaporation of sub-soil water, rich in calcium carbonate just near the soil surface. Oolite Recent carbonate muds can accumulate in the oceans in thick layers that are destined for limestone formation. A limestone variety caused by swift currents that rolled carbonate mud into small beads that (once solidified) look like tiny eggs is called an oolite and is used for ornamental applications. Calc-Sinter (calc-tuffa) It is white or light-colored calcareous rock (CaCO3) deposited from carbonate-rich springs. Travertine It is a type of limestone that forms in caves as a result of deposition of calcite from groundwater. Sedimentary Rocks Sedimentary Rocks Coals Coal - an organic sedimentary rock, is of biochemical origin. It is made up mostly Types of plant material and other organic matter, which accumulated in a swamp Peat It is porous mass of brownish plant fragments. Peat is the lowest grade coal that consists with stagnant, oxygen-deficient water. of slightly altered vegetable matter and may not be even considered as a coal. It has very low calorific value, high percentage of moisture and is rich in volatile matter. Composition It is a carbonate rock composed of the mineral dolomite, a calcium-magnesium carbonate Lignite It is also known as brown coal and forms the poorest grade of coal with calorific value [CaMg(CO3)2]. Ferrous iron is present in small proportions in some of its varieties. It is ranging between 6300–8300 BTU. It is compact and massive in structure with specific gravity similar to limestone in general appearance, but reacts with acid only when powdered. of 1.5 and hardness of 2.5. Some varieties of lignite may still show to a good extent the traces of original vegetable structure. It Uses is often crumbly, relatively moist and powdery. Coals form all-purpose fuels, some varieties being more suitable for specific industrial uses. Bituminous Coals These form a broad group of common coals having essential properties varying within wide limits. It is dull to shiny and black and is sooty. The fixed carbon ranges between 69–78% and the calorific value between 9,500 to 14,000 BTU. Their common character is that they contain enough volatile matter, which makes them quite soft on heating, and they start agglomerating. Some of bituminous coals may contain volatile matter to such a high extent as 30% of their bulk. Some such coals are typically banded in structure. Sedimentary Rocks Sedimentary Rocks Coal Iron Ores Types Composition Anthracite Coal It is considered the highest-grade coal with fixed carbon ranging between The iron ore beds occur interstratified in sedimentary rocks. Sedimentary iron deposits form 92–98%. It is actually considered to be metamorphosed bitumenous coal. Anthracite coal has from chemical reactions that combined iron and oxygen in marine and fresh waters, chiefly the highest calorific value in coals and as chemical precipitates in the form of oxides, carbonates and silicates, e.g. haematite burns almost without any smoke, as the volatile matter is negligible. It has a glassy luster, and (Fe2O3) and magnetite (Fe3O4). is blackish and denser, may have a slight golden shine as well; has low density and is not Uses sooty. It is largely used for heating domestically as it burns with little smoke. Most of the iron produced is used to make steel. Steel is used to make beams and columns