Formation Of Sedimentary Rock PDF

SEDIMENTARY ROCKS There are 2 ways sedimentary rocks are formed 1. Clastic are made from sediments lithified 2. Non-clastic: not lithified together---include chemical & biochemical/organic SEDIMENTARY ROCKS WILL CONTAIN FOSSILS. SEDIMENTARY ROCKS FORM IN LAYERS...

SEDIMENTARY ROCKS There are 2 ways sedimentary rocks are formed 1. Clastic are made from sediments lithified 2. Non-clastic: not lithified together---include chemical & biochemical/organic SEDIMENTARY ROCKS WILL CONTAIN FOSSILS. SEDIMENTARY ROCKS FORM IN LAYERS CALLED STRATA Oldest rocks are on the bottom….youngest on top This is a good example of Stratification  THE 2 CLASSES OF SEDIMENTARY ROCKS 1. CLASTIC Sedimentary Rocks are made from sediments that come from pre-existing rocks that have been weathered (breaking down into smaller pieces) and eroded (transported away) then compacted together. The 2 types of weathering include physical (only size changes) and chemical (a new substance is formed).  Sediments range in size from tiny pieces of clay to sand, to pebbles, and to stuff as big as boulders Clastic rocks form in a process called lithificaton which means compaction and cementation are occurring Here’s How They Form: Layers of sediment are deposited at the bottom of oceans and lakes As the layers build one on top of another, the pressure on the bottom layers COMPACTS the sediments together In the empty spaces between sediments, natural glues, like calcite, CEMENT the sediments together Demo of Sedimentation Look at the processes that are occurring in this animation Clastic Process  Examples of clastic sedimentary rocks include CONGLOMERATE BRECCIA SHALE SANDSTONE  2. Non-Clastic contain 2 types: chemical and biochemical CHEMICAL Sedimentary Rocks are made from mineral crystals that formed from chemicals dissolved in water. Here’s How They Form: The water in the oceans, lakes, and underground are often full of dissolved minerals like halite and calcite. Water evaporates leaving the solids behind: rock salt are formed when salt is left after evaporation and limestone is formed when calcite is left behind Chemical Sedimentary Rocks are also formed in caves where mineral-rich water drips from the ceiling, creating stalactites and stalagmites made out of limestone Limestone Cave Examples of chemical sedimentary rocks include limestone and rock salt Rock Salt Limestone  Chemical Sedimentary Rocks  These rocks form as a result of chemical weathering, dissolving chemicals and transporting them in solution. When conditions are right, these dissolved chemicals change back into a solid through the processes of; 1) Precipitation 2) Evaporation. Chemical sedimentary rocks are crystalline, that is made of crystals interlocked with each other. Conceptually, that is the same texture we see in igneous and metamorphic rocks, but NOT in clastic sedimentary rocks.  Chemical Sedimentary Rocks  Precipitation: Process where a change in environmental conditions cause chemicals dissolved in solution, to fall out of solution and forms a solid material. Most common in shallow water environments.  Evaporation: Process where there is a change in state from a liquid to a gas. Chemicals dissolved in the liquid (water) are left behind as a solid material.  Note: Evaporation and Precipitation often work together. As water evaporates, chemicals in solution will precipitate. Example: Rock Salt (Halite)  Sedimentary rocks  Chemical sedimentary rocks (Precipitation) Precipitates  Chemicals dissolved in solution, fall out of solution and forms a solid rock.  Results from a change in environmental conditions, such as;  Temperature, Concentration, or Chemical changes. Sedimentary rocks can also be crystalline, such as the crystalline limestones precipitated directly from solution; the term is not generally applied to the clastic sediments, even though they are formed largely from the accumulation of crystalline materials. Limestone and Rock Gypsum are two additional examples of common crystalline rocks.  Sedimentary rocks  Chemical sedimentary rocks (Precipitation) 1) Limestone  10% of all sedimentary rocks (by volume)  most abundant chemical sedimentary rock  composed primarily of calcite (calcium carbonate CaCO3)  formed by marine organisms (corals, clams, algae)  some deposited directly out of ocean or other waters Most abundant chemical precipitate rock which forms in shallow marine waters. Often contain shell fossils. Coral reef limestone mountain  Sedimentary rocks  Chemical sedimentary rocks (Precipitation) 2) Dolomite (Dolostone)  CaMg(CO3)2, Calcium Magnesium Carbonate  Dolomite appears to form in many different types of environment  Dolomite is used as an ornamental stone and a concrete aggregate.  It is an important Petroleum reservoir rock  Sedimentary rocks  Chemical sedimentary rocks (Precipitation) 3) Travertine  limestone deposited by springs.  Groundwater traveling through limestone beds dissolves calcium carbonate and as this dissolved matter precipitates it builds up travertine deposits.  "Travertine" is sometimes used to mean cavestone, the calcium carbonate rock that makes up stalactites and other cave formations.  Sedimentary rocks  Chemical sedimentary rocks (Evaporation) Evaporites  water evaporates and dissolved items are deposited  mostly marine (ocean) rocks, but some lakes  Salt (Halite), Gypsum and Sylvite Salt flats, Utah Death valley, Calif.  Sedimentary rocks  Chemical sedimentary rocks (Evaporation) Evaporites  water evaporates and dissolved stuff is deposited  Chemical Sedimentary Rocks Examples of chemical sedimentary rocks include; 4) Rock Salt  Consist of the mineral Halite.  Forms by evaporation of shallow seas and lagoons that have high concentrations of halite in solution. The mineral precipitates out of solution as the water evaporates.  Common use is table salt and road salt.  Chemical Sedimentary Rocks Examples of chemical sedimentary rocks include; 5) Rock Gypsum  Consist of the mineral Gypsum.  Forms by evaporation of shallow seas and lagoons that have high concentrations of gypsum in solution. The mineral precipitates out of solution as the water evaporates.  Common use is plaster and gyproc (drywall). Chemical Sedimentary Rocks and Depositional Environments (Summary) Environment Rock types Shallow Marine - gypsum, halite (rock salt), sylvite, limestone, dolomite Deep Marine/ocean - limestone, dolostone, chert Cave - travertine (stalactites and stalagmites)  Sedimentary rocks  Chemical sedimentary rocks (Biochemical) Biochemical  Sedimentary rock created when organisms use materials dissolved in air or water to build their tissue.  Examples include; -- Coquina -- Chalk -- Chert -- Limestone (Coral) -- Coal  Sedimentary rocks  Chemical sedimentary rocks (Biochemical) 6) Coquina  Organic rock of biochemical origin  Rock of shell fragments  Sedimentary rocks  Chemical sedimentary rocks (Precipitation) Agate 7) Chert  very fine grained silica  also called flint, jasper, agate  most formed in ocean  occurs as layers (beds) & as irregular blobs in limestone  marine creatures remove silica from sea water, make shells  Sedimentary rocks  Chemical sedimentary rocks (Biochemical) 8) Limestone (Coral)  formed as a result of organisms creating limestone from their shells. 9) Chalk  formed as a result of the build-up, compaction, and cementation of microscopic marine organisms (ex. Foraminiferia). 10) Coal  the end product of large amounts of plant material that has been buried and chemically altered over millions of years.  Biochemical Sedimentary Rocks and Depositional Environments (Summary) Environment Rock types Swamp - coal Shallow Marine - coquina, limestone (coral) Beach - coquina Deep Marine - chalk, chert  BIOCHEMICAL OR ORGANIC Sedimentary Rocks are made from remains of once-living plants or animals (organic matter) will be found near areas of lots of biological activity this is the sedimentary rock type with the most fossils Biochemical sedimentary rocks include: coquina, chalk, coal and limestone CHALK Made from dead COAL COQUINA animals Made from Made from LIMESTONE dead plants shells with fossils in it