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

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. Chemical Sedimentary Rocks

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

Corals and Snails Common Minerals: Calcite Calcite CaCO 3 Aragonite Aragonite CaCO 3 Dolomite Dolomite (CaMg)CO 3 Carbonates - Limestone Biochemical (corals) Bioclastic (chalk, coquina) Inorganic – chemical precipitate travertine tufa oolitic limestone

Limestone bioclastic Unlike other chemical sedimentary rocks, limestone is usually formed from loose sediment similar to clastic sediment. These kind of limestone are sometimes called bioclastic. acid test. 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. Calcitearagonite Dolomite 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

Some algae precipitate aragonite flakes and needles as skeletons. When they die, the skeletal bits become sand- and mud-sized carbonate sediment.

Lime mudstone Lime mudstone - limestone with mud-sized carbonate grains. Comes in many different colors, and frequently contains fossils.

Fig a Underwater dunes formed from carbonate sediment

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

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

Chalk Limestone formed from the microscopic calcite skeletons of tiny animals.

Shell Coquina Shells cemented together with little or no matrix

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

Dissolved Solids in Thermopolis Hot Spring Total Dissolved Solids 2373Nitrate (NO 3 ) 10 Hydrogen Sulfide (H 2 S) 4.5 Strontium 20 “Hardness” (CaCO 3 ) 1274Lithium 2 Thorium less than 0.6Barium 2 Bicarbonate (HCO 3 ) 755Aluminum 1 Silica (SiO 2 ) 82Chromium trace Iron (Fe) 03Calcium (Ca) Lead Boron 0.56 Magnesium (Mg) 76Manganese 0.02 Sodium (Na) 262Titanium 60 Potassium (K) 49Zinc 2 Sulfate (SO 4 ) 760Tungsten 0.01 Chloride (Cl) 328 Vanadium 0.1 Fluoride (F) 3.7 Copper trace

Siliceous Sedimentary Rocks Microcrystalline quartzopal 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.

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

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

Bedded Chert Another common mode of occurrence in sedimentary deposits.

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

Evaporite Production 1000 ft EvaporationEvaporation H2OH2O H2OH2O H2OH2O Example Example: Minerals formed from dissolved ions as seawater evaporates

Ionic Composition of Seawater Cl - 18,980 (SO 4 ) 2- 2,649 (HCO 3 ) Anions Na + 10,556 Mg 2+ 1,272 K Ca Cations parts per million Ions: 34,387 ppm H 2 O: 965,613 ppm 35 o/oo normal marine salinity Total NaCl Common Mineral Salts KMgCl 36H 2 O - Carnalite MgCO 3 - Magnesite CaMg(CO 3 ) - Dolomite CaSO 4 - Anhydrite KMgCl 36H 2 O - Carnalite MgCO 3 - Magnesite CaMg(CO 3 ) - Dolomite CaSO 4 - Anhydrite Other Mineral Salts Na Cl - Halite CaSO 4H 2 O K Cl KCl- Sylvite Ca SO 4 H2OH2O - Gypsum

Basin of Seawater 15 ft Gypsum - CaSO ft. Sylvite (KCl) and Mg-salts Halite - NaCl 11.8 ft ft Evaporation H2OH2O H2OH2O H2OH2O 2.6 ft. As the water evaporates, the ions become more concentrated, and different minerals precipitate.

Shores of the Great Salt Lake, Utah

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)

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. 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.

coal bed

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.