Sedimentary Rocks & Weathering
Sedimentary Rocks & Weathering 80203 - GEOL 1010-003
Popular in Physical Geology
Popular in Geology
This 14 page Class Notes was uploaded by Alex Casale on Sunday September 27, 2015. The Class Notes belongs to 80203 - GEOL 1010-003 at Clemson University taught by Mine Dogan in Summer 2015. Since its upload, it has received 94 views. For similar materials see Physical Geology in Geology at Clemson University.
Reviews for Sedimentary Rocks & Weathering
Yeah it helped me a lot.
copy of the powerpoint basically
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 09/27/15
Weathering amp Soil 92715 534 PM Weathering The physical breakdown and chemical alteration of rock at or near Earth s surface 0 Takes thousands of years 0 Temperature is extremely important Mechanical Weathering breaking rocks into smaller pieces 0 Frost Wedqinq Water will work its way into cracks of rocks the water will freeze and expand leading to the rocks fragmenting Sheeting exfoliation of igneous and metamorphic rocks 0 Confining pressure leads the rocks to crack 0 Cracks revealed through temperature changes 0 Never ending process until it consumes the entire material 0 Salt Crystal Growth sea spray or salty groundwater penetrates cervices and pore spaces in rocks 0 As the water evaporates salt crystals form and enlarge the crevices 0 Biological Activity disintegration resulting from plants and animals 0 Extremely fast compared others Chemical Weathering breaks down rock components and the internal structures of minerals Optimum environment is a combination of warm temperatures and abundant moisture Most important agent involved in chemical weathering is water responsible for transport of ions and molecules involved in chemical processes 0 1 Dissolvinq aided by small amount of acid in the water Soluble ions are retained in the underground water supply 0 2 Oxidizinq any chemical reaction in which a compound or radical loses electrons Important in decomposing ferromagnesian minerals Major Processes of Chemical Weathering Example how granite weathers o Chemically attacks by carbonic acid 0 Hydrogen ion attacks and replaces other positive ions 0 Most abundant product is clay minerals Weathering amp Characteristics that can Affect it Alterations caused by chemical weathering o Decomposition of unstable minerals 0 Generation or retention of materials that are stable 0 Physical changes such as the rounding of corners or edges spheroidal weathering Advanced mechanical weathering aids chemical weathering by increasing the surface area Other factors affecting weathering 0 Rock characterizes 0 Rock containing calcite marble and limestone readily dissolve in weakly acidic solutions 0 silicate minerals weather in the same order as their order of crystallization Rates of Weathering Climate Temperature and moisture are the most crucial factors Chemical weathering is most effective in areas of warm moist climates Differential Weathering m 2 Masses of rock do not weather uniformly because of regional and local factors Results in many unusual and spectacular rock formations and landforms One of the most indispensable resources A combination of mineral and organic water matter and air Regolith is rock and mineral fragments produced by weathering that supports the growth of plants Good Soil 0 25 air 0 25 water 0 45 mineral matter 0 5 organic matter Factors Controllinq Soil Formation o 1 Parent Material the source of the weathered mineral matter from which soils develop major influence new forming soil Residual soil parent material is the underlying bedrock Transported soil forms in place on parent material that has been carried rom elsewhere and deposted o 2 Time Important in all geologic processes Amount of time for soil formation varies for different soils depending on geologic and climate conditions The longer a soil has been forming the thicker it becomes and the less it resembles the parent material 0 3 Climate most influential control of soil formation key factors are temperature and precipitation Variations in temperature and precipitation determine whether chemical or mechanical weathering will predominate o 4 Plants and Animals Organisms influence the soil s physical and chemical properties Furnish organic matter to the soil 0 5 Topography Slopes steep slopes often have poorly developed soils optimum terrain is a flattoundulating upland surface Perfect soil is produced on smooth almost flat surfaces The Soil Profile Soil forming processes operate from the surface downward Vertical differences are called horizons which are zones or layers of soil 0 horizon organic matter A horizon organic and mineral matter E horizon little organic matter B horizon zone of accumulation C horizon partially altered parent material The O A E and B horizons together are called the solum or true soilquot 0 horizon Loose and partly decayed organic matter A horizon Mineral matter mixed with some humus E thl39IZOf Light celored 0 o O mineral particles Zone of eluvtation u v i 39 and leaching W i x b i w quot3 a V S 39 t v 39 Lo Bhonzon 39 39 39 39V 39 Accumulation of clay transported from above C lxm zon Partially altered parent material Unweathered parent material The impact of human activity on soils The agricultural productivity of soils can be improved through fertilization and irrigation Soils can be damaged or destroyed by careless activities Soil erosion is a natural process in the rock cycle Erosion rates are dependent on climate slope and type of vegetation Human activities such as deforestation and farming practices can enhance soil erosion Weathering and Ore Deposits Weathering creates deposits by concentrating metals into economically valuable concentrations secondary enrichment Bauxite principal ore of aluminum 0 Forms in rainy tropical climates from chemical weathering and the removal of undesirable elements by leaching o Other deposits 0 Weathering processes concentrate metals that are deposited through lowgrade primary ore Copper and silver Sedimentary Rocks 92715 534 PM Sedimentary Rocks record the history of Earth s surface Allows us to learn about past processes such as Climates Ecosystems dinosaurs fossils Catastrophes earthquakes tsunamis 0 Earth Systems hydrology erosion geotechnical It starts with weathering The formation of sediment processes that breakup and dissolve rock MechanicalPhysical break and crack 0 Chemical dissolve transform corrode oxidize Types of Sedimentary Rocks 0 1 Detrital clastic cemented together fragments and grains of preexisting rock Clast from klastos 2 Chemical nonclastic Minerals that precipitate directly from solution 0 3 Bio chemical made from shells of organisms 4 Organic Carbon rich relicts of plants 1 Detrital Clastic Sedimentary Rocks 0 Cemented together fragments and grains of preexisting rock Clast from klastos 0 Starts with mechanical aka physical weathering Breaks rocks into smaller grains or chunks Detritus and Clasts the weathered pieces gt2mm Gravel Coarse 1162mm Sand medium 0 1256116mm Silt mud fine lt1256mm Clay mud fine 0 COARSE MEDIUM FINE are key terms to be familiar with 0 Measure the millimeters of the rocks with seeds Particle sizes for detrital rocks Parti 1e Size Classification for Detrital Rocks Size Range millimeters Particle Name Common Sediment Name Detrital Rock gt256 Boulder 64 256 Cobble Gravel Conglomerate or breccia 4 64 Pebble 2 4 Granule 1 16 2 Sand Sand Sandstone 1 256 1 16 Silt Mud Shale mudstone or siltstone lt1 256 Clay 10 20 30 40 50 60 WW Copyright 2009 Pearson Prentice Hall Inc 0 How do they form 0 Weathering breaks down solid rock into smaller pieces 0 Erosion removes clasts from source and transports them 0 Deposition occurs when the rock can no longer be carried and are therefore left behind deposited o Steep narrow slopes and fast flowing water from the top of the mountain to the bottom is needed to transfer large materials 0 iCIicker Question The Clasts in this stream are all gravel size or larger Why The stream has carried away all the smaller particles high energy The source of these rocks must be near by short transport distance Clastic Sedimentary Rocks Grain Size 0 00000 Depositional energy of the environmental will determine grain size Fast pace due to steep slope high energy Coarse large grained Moderate pace due to moderate slope medium grained Slow pace hardly any slope low energy fine grained Course grains fall out faster than fine grains Slope steepness influences speed of transport Transport seed influences grain size Steep grade 9 fast water 9 deposits only large grains Gentle grade 9 slow water 9 deposits fine grain size 0 Clastic Sedimentary Rocks Sorting O O O Reflecting transport processes 9 well sorted materials more likely for long transport distances Well sorted sand all grain sizes are mostly equal Deltas stream into water body Beach faces wave action Wind blown sediments Poorly Sorted Sand obvious different grain sizes Sharp change in stream gradient Rock falls talus slopes Glaciers Clastic Sedimentary Rocks Grain Shape O 0 Short Distance from original source rugged shape large Moderate Distance from original source smoother shape but still rough medium size Long Distance from original source perfectly round and smooth small Know how grain size shape and sorting varies with maturity distance of transport Very poorly sorted 9 poorly sorted 9 moderately sorted 9 well sorted 9 very well sorted Angular rugged 9 subangular rugged by somewhat smoothed out 9 subrounded between smooth and angular 9 rounded completely smooth Clastic Sedimentary Rocks Digenesis o Recrystallization development of more stable minerals from less stable ones 0 Lithification unconsolidated sediments are transformed CompactionDewatering completely underwater n More grains on top of each other Cementation by calcite silica and iron oxide The cement fills spaces between grains See individual grains a Question How is this different with igneous rocks the crystals of igneous rocks grow into each other You cannot see the individual grains 0 Clastic Sedimentary Rocks Examples o SHALE Silt and claysized particles Form from the gradual settling of sediments in quiet nonturbulent environments Sediments form in thing layers that are called laminae Has fissility meaning the rock can be split into thing layers Crumbles easily and tends to form gentle slopes Most abundant sedimentary rock 0 SAN DSTON E Sandsized particles Forms in a variety of environments Second most abundant sedimentary rock Quartz is the most abundant mineral Quartz sandstone in predominately composed of quartz Arkose sandstone contains appreciable quantities of edspar Greywacke contains rock fragments and matrix in attrition to quartz and sandstone o CONGLOMERATE and BRECCIA Conglomerate consists of rounded gravelsized sediments Breccia consist of angular Sedimentary Rock Recap Sediments and sedimentary rocks cover approximately 75 of the earth They comprise about 5 by volume of Earth s outer 10 miles Contain evidence of past environments Sedimentary rocks are an important resource 0 Coal oil and other fossil fuels 0 Groundwater resources Sedimentary rocks are products of mechanical and chemical weathering Sediments and soluble constituents are typically transported downslope by gravity The sediments are then deposited and subsequently buried As deposition continues the sediments are lithified into sedimentary rocks There are 4 different types of Sedimentary Rocks 0 Detrital 0 Chemical 0 Biochemical 0 Organic Clastic Sedimentary Rock Recap Clastic detrital sedimentary rocks form from sediments that have been weathered and transported The chief constituents of detrital rocks include clay minerals quartz feldspars and micas Particle size is used to distinguish among the various rock types Sedimentary Rocks Continued 92715 534 PM 2 Chemical nonclastic Sedimentary Rocks 0 Form from precipitated material that was once in solution Precipitation of material occurs by 0 Inorganic processes such as evaporation 0 Organic processed from waterdwelling organisms form biochemical sedimentary rocks 0 Chemical Sedimentary Rocks Examples 0 LIMESTONE Most abundant chemical sedimentary rock Mainly composed of the mineral calcite Can form from inorganic and biochemical origins Inorganic limestone forms when chemical changes increase the calcium carbonate content of the water until it precipitates n Travertine is a type of limestone found in caves It s precipitated when the water in the cave loses carbon calcium n Ooitic limestone is composed of small spherical grains called ooids DOLOSTONE DOLOMITE Similar to limestone but contains magnesium Origin of dolostone is unclear Significant quantities of dolostone o CHERT Composed of microcrystalline quartz Forms when dissolved silica precipitates Flint jasper and agate are varieties of Chert o EVAPORITES 0 Form when restricted seaways become oversaturated and salt deposition starts 0 Rock salt and rock gypsum are two common evaporites o Occasionally evaporites 3 Biochemical 0 Biochemical limestone originates from the shells of marine organisms 0 Large quantities of marine limestone are formed from corals o Corals secrete a calcium carbonate skeleton and create reefs o Australia s Great Barrier Reef is the largest coral reef on Earth 0 Coquina a type of limestone is composed of cemented fragments of shell material 0 Chalk a type of limestoneO is composed of the hard parts of microscopic marine organisms 4 Organic Sedimentary Rocks Coal 0 Organic sedimentary rocks form from the carbonrich remains of organisms Occasionally plant structures leaves bark and wood identifiable in coal 0 Stages of Coal Formation o 1 Accumulation of plant remains o 2 Formation of peat o 3 Formation of lignite and bituminous coal 0 Formation of anthracite coal Diagenesis and Lithification 0 Many changes occur to sediment after it is deposited o Diagenesis chemical physical and biological changes that take place after sediments are deposited and buried Occurs within the upper few kilometers of earth s crust Examples recrystallization of more stable minerals from less stable ones for example aragonite to calcite o Compaction as sediments are buried the weight of the overlying material compresses the deeper o Cementation involves Sedimentary Rocks Continued 92715 534 PM Past Environments an environment of deposition or a sedimentary environment is a geographic setting where sediment is accumulating 0 determines the nature of the sediment that is accumulating 3 broad categories of sedimentary environments 0 continental 0 marine o transitional Continental Environments Dominated by stream erosion and deposition 0 at the top of the stream large sediment with jagged edges 0 bottom of the stream smaller sizes with more rounded edges fine sand clay slit Glacial o deposits typically unsorted mixtures of sediments that range from clay to boulder size 0 Wind eolian o well sorted 0 Example swamp o standing water low energy fine materials 0 lots of organic matter 0 find coal here 0 Example salt flats 0 has cracks o halite Marine Environments shallow 200m 0 boarders of worlds continents 0 receives huge quantities of terrestrial sediments o warm seas with minimal terrestrial sediments have carbonaterich muds turbidity current drop off from shelf to deep sea 0 you see bigger chunks here because its a drastic drop off Everywhere else you see fine grain in the deep sea 0 deep marine o primarily fine sediments that accumulate on the ocean floor o turbidity currents are the exception transitional environments 0 transition zone between marine and continental examples shoreline beaches tidal flats lagoons deltas o deltas low energy like swamp very well sorted Sedimentary Facies o the volume of sediment is all the same 0 different sediments often accumulate in adjacent environments 0 each facies possesses a distinctive set of characteristics reflecting the conditions of a particular environment 0 transitions between types are typically gradual Sedimentary Structures 0 provide info useful in interpretation of earth s history 0 Stratabeds the single most common and characteristic feature of sedimentary rocks Every stratum is unique 0 Types 0 Bedding planes what separates the strata 0 Cross Bedding A structure in which relatively thin layers are inclined at an angle to the main bedding Formed by currents of wind or water 0 Graded Beds The particles within a single sedimentary later gradually change from coarse at the bottom to fine at the top Rapid deposition from water containing sediment of varying sizes 0 Ripple Marks small waves of sand that develop on the surface of a sediment layer through the action of moving water or air 0 Mud Cracks indicate that the sediment in which they were formed was alternately wet and dry 0 Fossils the remains or traces of prehistoric life
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'