Sedimentary Rock Origins and Classification Our Core Principle Minerals and Rocks (and everything else) Are Stable Only Under the Conditions At Which They Form Change the Conditions and They Must Change Also Selected Igneous Rock Locations of the United States http://www.homepage.montana.edu/~ueswl/images/theilinpike.gif Our Core Principle Our Core Principle With weathering the two major sources of energy are: Tectonic Initial molten state + Radioactive heat + its counter force, gravity Heat causes things to expand which causes them to move Solar Heat from the sun Heat warms the air and water, setting up different pressures which causes them to move. Chemical Inorganic reactions, of which there are many, many, many – some of which we need to understand Biological Organic chemistry, plus biological modifications of environments The Simple Ideal Model of Sedimentary Rock Evolution Fractionation Processes At the Earth’s Surface The Simple Ideal Model for the Evolution of Sedimentary Rocks Average Continental Igneous Rock P 128 Granodiorite Quartz Sand Complete Weathering 3 Mixed Weathering Products Calcite Qtz Dissol. Clay Sand Calcite Separation During Transportation Kaolinite The Simple Ideal Model for the Evolution of Sedimentary Rocks The Simple Ideal Model for the Evolution of Sedimentary Rocks http://www.nku.edu/~biosci/CostaRica2003/Punta%20Marenco/Day3/CR%20SanJose%20to%20PM.htm The Simple Ideal Model for the Evolution of Sedimentary Rocks http://www.nps.gov/olym/elwha/photos/elwhamouth.htm The Simple Ideal Model for the Evolution of Sedimentary Rocks http://www.serf.tamus.edu/ResearchProjects/TexasInletsOnline/BrazosRiverMouth/Brazos%20River%20Main.htm The Simple Ideal Model for the Evolution of Sedimentary Rocks Qtz Clay Calcite Sand Separation During Transportation Beach Near Shelf Far Shelf Qtz. Sandstone Shale Limestone The Simple Ideal Model for the Evolution of Sedimentary Rocks Muav Limestone Bright Angle Shale Tapeats Qtz ss http://www.serf.tamus.edu/ResearchProjects/TexasInletsOnline/BrazosRiverMouth/Brazos%20River%20Main.htm Middle Cambrian - 510 Begin first major sea level rise http://jan.ucc.nau.edu/~rcb7/nam.html Late Cambrian - 500 http://jan.ucc.nau.edu/~rcb7/nam.html Early Ordovician - 485 Transcontinental Arch Antietam http://jan.ucc.nau.edu/~rcb7/nam.html Weathering Processes Mechanical Weathering • Making little pieces out of big ones. • Composition of original rocks does not change. • Result: lithic fragments Chemical Weathering • Original minerals chemically break down. • Result: formation of new minerals stable at Earth-surface conditions. Mechanical Weathering Frost Wedging via Freeze and Thaw http:faculty.uaeu.ac.ae~afarragphysical%20geologyw Mechanical Weathering Frost Wedging via Freeze and Thaw http://www.utexas.edu/depts/grg/hudson/grg301c/hudson_grg_301c/schedule/4_water_geomorph_images/10_weathering/2.htm Mechanical Weathering Frost Wedging via Freeze and Thaw http://www.gly.fsu.edu/%7Esalters/GLY1000/10Weathering_Erosion/Slide27.jpg Mechanical Weathering Plant Wedging http://www3.famille.ne.jp/~kazuo/SR-044.jpg Mechanical Weathering Exfoliation http://www.calstatela.edu/faculty/acolvil/weathering.html http:www.gly.fsu.edu~saltersGLY100010Weathering_Erosio Chemical Weathering • Original minerals chemically break down. • Result: formation of new minerals stable at Earth-surface conditions. Chemical Weathering Dissolution Carbonic Acid CO2 + H2O H2CO3 + H2CO3 H + HCO3 + ++ - CaCO3 +H Ca + 2 HCO3 Calcite/Limestone Dissolved Bicarbonate Calcium Ion Chemical Weathering Dissolution of Limestone http:edutel.musenet.org:8042gravenetimagesclose Chemical Weathering Dissolution of Limestone http:web.mala.bc.cageoscapeKarst.htm Chemical Weathering Dissolution of Limestone http:www.the-spa.comhanauergalleryLurayc Chemical Weathering Dissolution of Limestone http:firupe.free.frGreecePhoto27g27The_Kar Chemical Weathering Dissolution of Limestone http:www.people.auckland.ac.nzFrancesClassical%20ArtClassical%20Architect.%20Sc Chemical Weathering Dissolution of Limestone http:www.calvin.eduacademicclaspathwaysdelphida http:www.people.auckland.ac.nzFrancesClassical%20ArtClassical%20Architect.%20SculptureErechtheionKaryatids.JPG Chemical Weathering Oxidation 4 FeSiO3 + O2 + 8 H2O Pyroxene . 4 FeO(OH) nH2O + 4 SiO4 Limonite Goethite Chemical Weathering Oxidation Chemical Weathering Hydrolysis KAlSi3O8 + H2CO3 + 12 H2O Orthoclase Dissolved Silica + - 4 2K + 2HCO3 + 5H4SiO + + Al2Si2O5(OH) Kaolinite Clay KAl3Si3O10(OH) Chemical Weathering Hydrolysis http://faculty.uaeu.ac.ae/~afarrag/physical%20geology/physical5.htm Chemical Weathering Hydrolysis View of the Salisbury Crags sill from the Radical Road. Looking northeast. Spheroidal weathering is best seen in the centre of the image. The field of view is approximately 4 m. http://www.earthsci.gla.ac.uk/Holyrood7/Images/glacial/spweath.jpg Chemical Weathering Hydrolysis http://epswww.unm.edu/facstaff/gmeyer/eps481/images/corestones.jpg Chemical Weathering Hydrolysis http://www.calstatela.edu/faculty/acolvil/weathering/spheroidal2.jpg Mobility of Weathering Products Very Ca>Na>Mg>K>Si>Fe>Al Immobile Mobile This provides the differences needed for fractionation and evolution to take place. Fast Weathering Slow Weathering No Weathering Mobility of Weathering Products A Chemical Fractionation Process Very Ca>Na>Mg>K>Si>Fe>Al Immobile Mobile Bauxite Laterite Soil P 131 Basic Question: compared to the igneous rocks they started as, is the composition of a clastic sedimentary rock higher on the reaction series, lower on the reaction series, or at the same place? Soluble Soluble The sea is salty Soluble The sea is salty Clastic Rocks Carbonate Rocks Basic Question: compared to the igneous rocks they started as, is the composition of a clastic sedimentary rocks higher on the reaction series, lower on the reaction series, or at the same place? Clastic sedimentary rocks (sandstones and shales) evolve. Fates of Weathering Products The Simple Ideal Model for the Evolution of Sedimentary Rocks Average Continental Igneous Rock Granodiorite Quartz Sand Complete Weathering Mixed Weathering Products Calcite Qtz Clay Calcite Sand Separation During Transportation Beach Clay Near Shelf Far Shelf Sandstone Shale Limestone Weathering of Igneous Rocks Weathering Sedimentary Rock Mineral Cation Produce Outcome Olivine Fe Hematite/ Stains Mg Limonite (yellow, brown, red) Gabbro Pyroxene CaCO3 Limestone Ca plagioclase Ca calcite CaSO4 gypsum Gypsum Fe Hematite/ Stains Amphibole Mg Limonite (yellow, brown, red) Diroite Na plagioclase Na NACl halite Rock Salt Orthoclase K Kaolinite Clay/ Alkali Shale granite Quartz Quartz Quartz Sand grains Classifying Sedimentary Rocks with Ternary Diagrams The Simple Ideal Model for sedimentary rocks results in three end members: quartz sand, clay, and calcite in solution. Things show up in threes a lot when we look at the Earth, and many classifications are based on threes – that is a triangular (or ternary) diagram. Reading Ternary Diagrams Scale line Adds to 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Base line = 0% Reading Ternary Diagrams 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 100% 90% 80% 70% 60% 50% 40% Reading Ternary Diagrams Ternary Reading 30% 20% 10% 80% 80% 60% 60% 50% 50% 30% 30% 10% 10% 70% 70% 40% 40% 20% 20% 100% 100% 90% 90% Reading Ternary Diagrams P 131 Reading Ternary Diagrams A SS 50% SH 20% LS 30% A Reading Ternary Diagrams A SS 50% D SH 20% SS 20% LS 30% SH 40% LS 40% C B SS 10% SH 70% LS 20% A C SS 80% SH 20% LS 00% D B Naming Sedimentary Rocks A SS 50% SandstoneShaley-limey Sandstone SH 20% LS 30% B SS 10% SH 70% Sandy-limey Shale LS 20% C SS 80% SH 20% Shaley Sandstone LS 00% D SS 20% Sandy-shaley Limestone SH 38%40% LS 40%42% Sedimentary Rock Classification Clastics Carbonates Evolution of Clastic Sediments on a Ternary Diagram Sediment Evolution on a Ternary Diagram 11The Q, FL, and M Axes Quartz Ca Plagioclase Na Plagioclase Orthoclase Clay (matrix) Feldspar (shale) Lithics Sediment Evolution on a Ternary Diagram 22Igneous Rock Composition Quartz Plagiogranite Q = 30% F = 65% L = 05% Granite Gabbro & Clay (matrix) Syenite Feldspar/ (shale) Lithics Q = 00% Q = 00% Gabbro F = 45% Syenite F = 80% L = 55% L = 20% 30% Q 70% clay Clay (matrix) Sedimentary Rocks (shale) Quartz Weathering s k oc weathering R s Feldspar/lithics to clay Sediment Evolution on a Ternary Diagram ou e n g I 33 Granite Lithics Feldspar/ 30% Q 70% F & L Sediment Evolution on a Ternary Diagram 44Sorting Quartz Sand goes to top Stays on beach 30% Q 30% Q Granite sorting 70% F & L 70% clay Clay goes to bottom Near shore shelf Clay (matrix) Feldspar/ (shale) Lithics Sediment Evolution on a Ternary Diagram 55Step by Step Weathering Quartz 30% Q 70% F & L CLAY Completed Weathering 10 clay 20 30 40 50 60 60 FL 50 40 30 20 10 30% Q 30% Q Granite 70% F & L 70% Clay Clay (matrix) Feldspar/ (shale) Lithics Sediment Evolution on a Ternary Diagram 66Step by Step Weathering Quartz 10 % line for F & L 25 % line for F & L 60 Q 10 clay 20 30 40 40 FL 30 FL 20 10 30 Completed Weathering 10 clay 20 30 40 50 60 60 FL 50 40 30 20 10 30% Q Granite 70% Clay Clay (matrix) Feldspar/ (shale) Lithics The last sliver has mostly quartz, or clay, or mixed quartz and clay. Clay (matrix) (shale) Quartz Quartz ss Quartz wacke Shale 10% line SubS-ufebl-dfespldaspthaicthoicr wsuabc-kliethic 25% line Naming the Rocks This area is approaching the end wacke of weathering; F & L are down Feldspathic(arkosic) to between 10 and 25%. Sediment Evolution on a Ternary Diagram or, Lithic e.g. a lithic