2/3/20141Sediments and Sedimentary RocksSolidified Weathering ProductsSan Juan River, UTSan Juan River, UTSize Sorting•The different minerals that form as weathering products have different characteristic grain sizes.•Un-weathered material has largest grain size.•Quartz sand is 0.1 to 2 mm.•Clays are less than 0.001 mm (1μm).•Ca+2, Na+1, CO3-2, SO4-2, and Cl-are dissolved.Particle Sizes2/3/20142Size-Sorting Gives Different Sedimentary Rocks•Breccias have moved very little.•Conglomerates are near-source continental.•Sandstones are continental.–Eolian sandstones are desert deposits.–Fluvial sandstones are river deposits.•Shales are shallow marine (salt water).•Limestones are tropical shallow marine (reefs).•Evaporites result from evaporation of seawater.Depositional EnvironmentsBreccias, Conglomerates SandstonesShalesLimestones (tropical)2/3/20143Granite Weathering•Quartz: Sand•Feldspar: Clay•Mica: ClayConglomerates and Breccias•Breccias are composed of coarse, angular fragments. –Breccia fragments have not traveled far.•Conglomerates are composed of coarse, rounded fragments–Conglomerate fragments have traveled further•Conglomerates and Breccias are typical of continental alluvial fansConglomerate - Breccia Breccias, ConglomeratesBreccias, ConglomeratesSandstones•Arkose contains feldspar and is near-source–Fountain Formation (Flatirons) is made of arkose and conglomerates•Eolian sandstones are desert (wind) deposits–Commonly show cross-bedding•Fluvial sandstones are stream deposits–Commonly have asymmetric ripples and channels.2/3/20144Eolian Sandstone:Cross-beddingEolian Sandstone:Cross-beddingEolian Sand DunesSandstone MicrographQuartz grainsAsymmetric ripples(looking upstream)RipplemarksFluvial(River)Sandstone2/3/20145SandstonesOrganic Sediments•Swamp and bog deposits rich in organic matter lithify to form coal.–Peat is the first stage.–Lignite is peat that has begun to lithify.–Bituminous coal is an abundant energy source.–Anthracite is metamorphosed coal.–Petroleum and natural gas are also derived from organic sediments.Organic SedimentsOrganic Sediments•This carbon is taken from the atmosphere as CO2and reduced by photosynthesis to carbon and hydrocarbons plus oxygen.•The oxygen goes to the atmosphere.•The reduced carbon is buried.•When the carbon is burned the CO2goes to atmosphere.•The energy comes from where?Shales and Mudstones•Clay and silt can only be deposited in standing water.•Clays are layer-silicates (like mica) and grains align so layers are parallel•Shale breaks along the layers and is said to be fissile.•Mudstones and siltstones are massive (don’t break along layers).Shales and Mudstones2/3/20146•The most abundant mineral in shale is clay.•Shale breaks along the layers and is said to be fissile.•Shales were deposited in standing water.MudcracksShalesLimestone•Limestone is made of calcite (CaCO3).•Most Phanerozoic limestones are biogenic (formed by critters).•Seawater is saturated in calcium carbonate.•Calcite is more soluble in cold water than warm.•Limestone is tropical marine.•Dolomite is calcium-magnesium carbonate CaMg(CO3)2.Most limestone is biogenicMost limestone is biogenic2/3/20147Most limestone is biogenicLimestone (calcite) is soluble in water.Caverns form in limestone.Caverns form in limestone.Limestones (tropical)Dolomite and Limestone OutcropDolomites, ItalyCalcium Carbonate Saturation in Little Colorado River2/3/20148Calcium Carbonateis saturated in warm seawaterEvaporites•Evaporites are rocks deposited from evaporating seawater.•As seawater evaporates, the sequence of minerals deposited is: –1) calcite (CaCO3)–2) gypsum (CaSO4·2H2O)–3) halite (salt) (NaCl)–4) sylvite (KCl)Evaporites: Solution mining of sylvite (KCl) at Potash, UTSan Juan River, UT: coastal sediment sequenceLimestone-shale-sandstoneSize-Sorting Gives Different Sedimentary Rocks•Conglomerates are near-source continental•Sandstones are continental–Eolian sandstones are desert deposits–Fluvial sandstones are river deposits•Shales are shallow marine (salt water).•Limestones are also shallow marine.•Evaporites result from evaporation of seawater.Depositional Environments2/3/20149Sedimentary Terms•Boulder (>256mm)•Cobble (64-256mm)•Pebble(2-64mm)•Sand (.06-2 mm)•Silt (4 – 60 μm)•Clay (<4 μm)•Conglomerate•Breccia•Arkose•Sandstone•Siltstone•Shale•Limestone•Evaporite•Reef•Lithification•Cross bedding•Ripple marks•Alluvial•Fluvial•EolianSedimentary Short Essays• 6. How do the weathering rates of the different minerals in granite give rise to different grain sizes of the weathering products?•• 7. How does the transport of sediments (weathering products) by wind and water result in the different sedimentary rocks having different compositions?•••Short Essays• 1. What is a mineral and how does it differ from a rock?•• 2. What are protons, neutrons, electrons, isotopes and elements and how are they formed?•• 3. What is igneous fractionation and how does it account for the differences between mantle, oceanic crust and continental crust?Short Essays4. What is the scientific method and how is it used to draw conclusions about the origin and age of the Earth?•• 5. What are the two major energy sources that drive Earth processes and which processes does each primarily control?••Clicker Question•What is the most likely geologic setting in which limestone was deposited?–A. Continental alluvial fans–B. Continental deserts and beaches –C. Shallow-water marine–D. Deep-water marine –E. Reefs(Tropical Shallow Marine)2/3/201410Clicker Question•What is the most likely geologic setting in which limestone was deposited?–A. Continental alluvial fans–B. Continental deserts and beaches –C. Shallow-water marine–D. Deep-water marine –E. Reefs (Tropical Shallow Marine)Clicker Question•What is the most likely geologic setting in which conglomerate was deposited?–A. Continental alluvial fans–B. Continental deserts and beaches –C. Shallow-water marine–D. Deep-water marine –E. ReefsClicker Question•What is the most likely geologic setting in which conglomerate was deposited?–A. Continental alluvial fans–B. Continental deserts and beaches –C. Shallow-water marine–D. Deep-water marine –E. ReefsClicker
View Full Document
Unlocking...