Sedimentary Rocks

1. Sedimentary Rocks • Chemical Sedimentary Rocks • Limestone • Chert – Silica • Evaporites • Organic Rocks • Coal • Oil and natural gas

2. Chemical Sedimentary Rocks Clastic Sedimentary Rocks Formed from clasts (bits and pieces of pre-existing rocks) transported, deposited,and lithified Chemical Sedimentary Rocks Formed from precipitation of minerals within the depositional basin. Includes biominerals, evaporites, coal, chert, etc.

3. Evaporites minerals precipitated from evaporating water Siliceous Rocks Silica and opalline silica precipitate either organically or inorganically Coal and Peat Carbon-rich deposits formed from build-up of plant material in swamps Carbonates Variety of limestones composed of calcite, aragonite, and dolomite precipitated either organically or inorganically http://csmres.jmu.edu/geollab/Fichter/SedRx/chembiokey.html

4. Corals and Snails • Common Minerals: • Calcite CaCO3 • Aragonite CaCO3 • Dolomite (CaMg)CO3 • Carbonates - Limestone • Biochemical (corals) • Bioclastic (chalk, coquina) • Inorganic – chemical precipitate • travertine • tufa • oolitic limestone

5. Limestone Unlike other chemical sedimentary rocks, limestone is usually formed from loose sediment similar to clastic sediment. These kind of limestone are sometimes called bioclastic. It is therefore relatively easy to mistake limestone for a clastic rock unless you perform an acid test. Carbonates will react with acid; clastic sediments will not. Calcite and aragonite react energetically with rather weak acid. Dolomite will react sluggishly, and usually needs to be ground up to see a reaction with weak acid. Snails

6. Some algae precipitate aragonite flakes and needles as skeletons. When they die, the skeletal bits become sand- and mud-sized carbonate sediment. http://www.turtles.org/

7. http://www.ndc.edu/stones/newpage16.htm http://www.geo.mtu.edu/FIELD_TRIPS/florida/ Lime mudstone - limestone with mud-sized carbonate grains. Comes in many different colors, and frequently contains fossils. http://seis.natsci.csulb.edu/bperry/Sedimentary%20Rocks%20Tour/biochemical_sedimentary_rocks.htm

8. Underwater dunes formed from carbonate sediment Fig. 06.22a

9. Stony corals precipitate sometimes massive aragonite skeletons, which break up to form boulder- to mud-sized carbonate sediment.

10. Fringing coral reef around a island. As the volcanic island sinks, the coral growth keeps up, eventually forming a coral atoll.

11. Chalk Limestone formed from the microscopic calcite skeletons of tiny animals. http://earthobservatory.nasa.gov/Library/Coccolithophores/

12. Shell Coquina Shells cemented together with little or no matrix http://www.dep.state.fl.us/geology/geologictopics/rocks/anastasia.htm

13. Inorganic Carbonates • Limestone precipitated from dissolved ions in water, including: • Seawater • Hot springs • Groundwater • Evaporating basins • Pore water

14. Dissolved Solids in Thermopolis Hot Spring Total Dissolved Solids 2373 Nitrate (NO3) 10 Hydrogen Sulfide (H2S) 4.5 Strontium 20 “Hardness” (CaCO3) 1274 Lithium 2 Thorium less than 0.6 Barium 2 Bicarbonate (HCO3) 755 Aluminum 1 Silica (SiO2) 82 Chromium trace Iron (Fe) 03 Calcium (Ca) Lead 0.004 Boron 0.56 Magnesium (Mg) 76 Manganese 0.02 Sodium (Na) 262 Titanium 60 Potassium (K) 49 Zinc 2 Sulfate (SO4) 760 Tungsten 0.01 Chloride (Cl) 328 Vanadium 0.1 Fluoride (F) 3.7 Copper trace http://www.thermopolis.com/

15. Siliceous Sedimentary Rocks Microcrystalline quartz and opal precipitated from dissolved ions in sedimentary environments. Can be precipitated organically or inorganically. Microcrystalline quartz can also precipitate in pore spaces to form cement. http://www.diskworks.com/octoberopals/opal1.html

16. Scanning Electron Micrograph (SEM) of tiny, siliceous skeletons of radiolarians, which are a source silica chert

17. Chert nodules common occurrence of chert in other sedimentary rocks (this is limestone) Fig. 06.23a

18. Bedded Chert Another common mode of occurrence in sedimentary deposits.

19. Evaporites Minerals (halite, gypsum, sylvite etc.)precipitated from dissolved ions in basins from which water is evaporating.

20. H2O H2O Evaporation H2O Evaporite Production 1000 ft Example: Minerals formed from dissolved ions as seawater evaporates

21. Cations Anions Total Ions: 34,387 ppm H2O: 965,613 ppm 35 o/oo normal marine salinity Na+ 10,556 Mg2+ 1,272 K+ 380 Ca2+ 400 Cl- 18,980 (SO4)2- 2,649 (HCO3)- 140 parts per million Other Mineral Salts KMgCl3•6H2O - Carnalite MgCO3 - Magnesite CaMg(CO3) - Dolomite CaSO4 - Anhydrite Ionic Composition of Seawater Na Cl Cl H2O SO4 K Ca Common Mineral Salts NaCl - Halite KCl - Sylvite CaSO4•H2O - Gypsum

22. H2O H2O Evaporation H2O Basin of Seawater As the water evaporates, the ions become more concentrated, and different minerals precipitate. 1000 ft Sylvite (KCl) and Mg-salts 2.6 ft. 11.8 ft. 15 ft Halite - NaCl Gypsum - CaSO4 0.5 ft.

23. Shores of the Great Salt Lake, Utah http://speclab.cr.usgs.gov/PAPERS.calibration.tutorial/

24. Coal Sedimentary rock formed from the remains of plant material • Coal comes in various grades, depending on the amount of post-depositional alteration: • Peat • Lignite • Bituminous coal • Anthracite (a metamorphic rock) http://geoinfo.nmt.edu/education/litegeology/images/coal.gif

25. Coal is formed from swamp deposits It is derived from woody plants The buried material is compressed and heated in the Earth, driving off the water, increasing the carbon content. Higher carbon content = higher grade fuel Coal almost always contains pollution-causing impurities. http://www.fmnh.org/

27. coal bed

28. Oil and Natural Gas Formed when microscopic organisms die and accumulate in an area of low oxygen, preserving organic matter. When sediments are compacted and heated, organic matter is transformed into hydrocarbons, producing oil and natural gas. http://www.sohoblues.com/GulfWarWeb/previewpages/previewpage5.htm