Popular in Geology
Popular in Geology
This 3 page Class Notes was uploaded by Ashley Barry on Tuesday January 26, 2016. The Class Notes belongs to 1610 at University of North Texas taught by Johnny Byers in Fall2014. Since its upload, it has received 10 views. For similar materials see Geology in Geology at University of North Texas.
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Date Created: 01/26/16
Geology notes -Sedimentary rocks Sedimentary-latin- sedimentum=settling study of sedimentary rocks ,processes by which they were formed,the description ,classiﬁcation,origin,and interpretation of sediments 75% of all rocks cropping are sedimentary by volume-5% of outer 10 miles of earths surface are sedimentary current erosion rates sedimentary rocks provide us with the clues we need to interpret our earths history to reconstruct ancient environments we have to look at lithology 2 diff ways spacial vs temporal spatial-times and conditions in one particular area temporal-how it evolved through time by comparing several outcrops three basic types detrital-sandstone,conglomerate,shale chemical-limestone,dolomite,travertine organic-coquina,chalk,lignite origin -transported (ice,wind,gravity,river)-environment where comes to rest(ocean=combination=small graination) (wind=desert)-lithiﬁcation lithiﬁcation: physical-compaction/consolidation-cementation-detrital sedimentary / igneous clastic sediments chemical-precipitation/cementation-chemical biological-organic origins-late cementation-biogenic or biochemical sedimentary -biogenic volcanoclastic- volcanoclastic sediments classify sediments: texture and composition Physical clastic rocks terrigenous deposits that consist of fragments of pre-existing rocks which were transported and deposited by physical processes identiﬁed by particle size/grain size lithiﬁcation-processes that compact ,consolidate,and cement the rocks together particle to grain size sand: 2mm-62 um silt:62 um-4 um clay-less than 4 um ﬁve common types of cements calcite caco3 silica si02 limonite feoh3nh2o hematite fe2o3 claystone or mudstone are called shale siltstone called shale sedimentary rocks created by evaporation (evaporites,playa lake,salt pan) chemical sedimentary rocks are named based on composition and texture allochthonous are sedimentary rocks that were formed from transported sediments autochthonous are formed in place inorganic sedimentary rocks halite gypsum calcite limestone dolomite elements in sea water: sodium and chloride are 2 dominant CA k nA cl s04 co2 o mg h common minerals remaining after seawater evaporate dolomite,scrape off to get powder potassium chloride sodium chloride gypsum calcite,limestone anhydrite biogenic,biogenous rocks organic rock produced directly by physiological activities or organisms ,either plant or animal biogenic rocks-limestone,chert,chalk,coal phytoplankton examples :diatoms,dinoﬂagellates (can be found in salt or fresh water) coal formation process peat(partially altered plant material) - burial compaction lignite(soft brown coal) -greater burial compaction bituminous (soft black coal) -metamorphism anthracite(hard black coal) tuff rock is volcanoclastic sedimentary rock Breccia and conglomerate are very similar rocks. They are both clastic sedimentary rocks composed of particles larger than two millimeters in diameter. The difference is in the shape of the large particles. In breccia the large particles are angular in shape but in conglomerate the particles are rounded. sedimentary rocks provide clues we need to interpret our earth history lithiﬁcation process:compaction or cementation chemical rocks process
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