3Sedimentary rocksSedimentary rocks are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. OrSedimentary rocks are formed by the lithification of inorganic and/or organic sediments, or as chemical precipitates.
4CLASSIFICATION OF SEDIMENTARY ROCKS There are two types of sedimentary rocks:1. Clastic2. Chemical
5Clastic sedimentary rocks Clastic sedimentary rocks form when existing parent rock material is weathered, fragmented, transported, and deposited in layers that compact, cement, and lithify to form sedimentary rocks.
6Chemical sedimentary rocks Chemical sedimentary rocks are formed by a variety of processes and are divided into sub-categories including inorganic, and biochemical or organic chemical sedimentary rocks.
7Clastic sedimentary rocks Few examples of clastic sedimentary rocks areLimestoneBrecciaChertSandstoneShaleMudstoneConglomerate
8Chemical sedimentary rocks Few examples of chemical sedimentary rocks areFlintChertJasperDolomiteMagnesiteRock saltGypsum
11Classification of Clastic sedimentary rocks S.NOTYPEGRAIN SIZEROCK1.GRAVELSBoulders>256mmConglomerateCobbles16-256mmPebbles2-16mm2.SANDSCoarse½ -2 mmQuartz sandstoneMedium¼ - ½ mmFine1/16 – ¼ mm3.SILTS1/256-1/16 mmShale, Siltstone4.CLAYS< 1/256mmMudstone
12CLASSIFICATION OF CHEMICAL SEDIMENTARY ROCKS S.NOTYPESUB-TYPECHARACTERISTICS1.CHEMICALLY FORMED ROCKSSiliceous(Flint, chert, jasper)Silica is chief constituentCarbonate(Dolomite , magnesite)Precipitated from carbonate rich watersFerruginousOxides and hydroxides are common examplesPhosphaticForm from sea water rich in phosphoric acidEvaporites(Rock salt, gypsum)Formed from evaporation
13S.NOTYPESUB-TYPECHARACTERISTICS2.ORGANIC DEPOITSCarbonateFormed by gradual accumulation of shells and skeletal bones of sea organismCarbonaceous(Coal)They are rich in carbon its main source is plantsPhosphatic Deposits-GuanoAccumulation of excreta of some birdsFerruginousDepositsMostly iron carbonate deposits , from fresh water lakes
15Chert Chert is composed of silicon dioxide (SiO2). It occurs as nodules, concretionary masses and as layered deposits.Chert is a very hard material that produces a spark when it is struckagainst steel. The heat fromthis spark can be used tostart fires
16LimestoneLimestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear,warm,shallow marine waters. Limestone can also form through evaporation. Stalactites, stalagmites and other cave formations (often called "speleothems") are examples of limestone that formed through evaporation.
17BrecciaBreccia are composed of large angular fragments (over two millimeters in diameter). The spaces between the large angular fragments can be filled with a matrix of smaller particles or a mineral cement that binds the rock together. Breccia forms where broken,angular fragments of rock ormineral debris accumulate.Possible location for breccia formationis at the base of an outcrop where mechanical weathering debris accumulates or alluvial fan. Some breccias form as debris flow deposits.
18ConglomerateConglomerate is a rock consisting of individual clasts within a finer-grained matrix that have becomecemented together.Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts. Both conglomerates and breccias are characterized by clasts larger than sand (>2 mm)