Laboratory Manual for Introductory Geology 4e

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Using SedimentaryRocks to InterpretEarth History6The beds of Grand Canyon National Park in Arizona are one of the most extensive sequences ofsedimentary rocks in the world.143
LEARNINGOBJECTIVES■■Understand the processes bywhich sedimentary rocks form■■Understand how geologistsclassify sedimentary rocksbased on their origin■■Become familiar withsedimentary rock textures andmineral assemblages■■Use texture to identify theagent of erosion involved information of sedimentaryrocks■■Use sedimentary rock texturesand minerals to interpretancient geography andclimateMATERIALSNEEDED■■Set of sedimentary rocks■■Magnifying glass or hand lens,microscope, and thin sectionsof sedimentary rocks■■Mineral-testing supplies(streak plate, glass plate. etc.)■ ■ Glass beaker, concentratedCa(OH) 2(calcium hydroxide)solution, straws6.1 IntroductionLike igneous rocks, sedimentary rocks form from previously existing rocks—but byvery different processes. If you’ve ever seen shells on a beach, gravel along a riverbank,mud in a swamp, or sand in a desert, you’ve seen sediment. Sediment consistsof loose grains (clasts) that may be made of individual minerals or fragments ofpreviously existing rock containing several minerals. Sedimentary rock forms at ornear the Earth’s surface by the cementation and compaction of accumulated layersof these different kinds of sediment.Sedimentary rocks preserve a record of past environments and ancient life andthus record the story of Earth history—once you know how to read it. For example,the fact that a sedimentary rock called limestone occurs throughout North Americameans that in the past, a warm, shallow sea covered much of the continent. Geologistshave learned to read the record in the rocks by comparing features in sedimentaryrocks with those found today in environments where distinct types of sedimentform (remember, the present is the key to the past). In this chapter, you will developthe skills needed to read the history recorded in sedimentary rocks.6.2 Sediment Formation and Evolution6.2.1 The Origin of SedimentThe materials from which sedimentary rocks form ultimately come from weathering—the chemical and physical breakdown of pre-existing rock. Weathering producesboth loose pieces, called clasts, and dissolved ions, which are charged atoms in awater solution. Once formed, clasts may be transported by water, wind, or ice toanother location, where they are deposited and accumulate. Dissolved ions, meanwhile,enter streams and groundwater. Some of these ions precipitate from groundwaterin the spaces between clasts, forming a cement that holds the clasts together.Other ions get carried to lakes or seas, where organisms extract them to form shells.Finally, some dissolved ions precipitate directly from water to form layers of newsedimentary minerals. In some environments, sediment may also include organicmaterial, the carbon-containing compounds that remain when plants, animals, andmicroorganisms die.6.2.2 Weathering and Its Influenceon Sediment CompositionThe minerals in sediment depend both on the composition of the source rocks andon the nature of the weathering the source rocks were exposed to. Let’s look first atweathering processes and how they influence sediment composition.Physical weathering breaks rock into fragments called clasts, as does hitting arock with a hammer, but does not change the minerals that make up the rock. Initially,clasts are simply small rock pieces and may contain many mineral grains or crystalsthat retain their original sizes and shapes. But as physical weathering progresses,the clasts break into smaller pieces, each consisting of a single mineral grain. Whilemoving along in wind and water, clasts grind and crash against one another andbecome progressively smaller. As a result, the sizes and shapes of transported clastsdo not tell us whether the source rock itself was coarse- or fine-grained, or whethergrains in the source rock interlocked or were cemented together (FIG. 6.1). Butbecause physical weathering does not change the composition of clasts, we canget a sense of the composition of the source rock by looking at what minerals the144 CHAPTER 6 USING SEDIMENTARY ROCKS TO INTERPRET EARTH HISTORY
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LABORATORY MANUALFOR INTRODUCTORY G
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CONTENTSPreface viiCHAPTER 1Setting
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CHAPTER 8Studying the Earth’s Lan
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PREFACEThis laboratory manual is ba
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exercises interspersed throughout t
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Supplements(available for download
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ABOUT THE AUTHORSAllan Ludman is Pr
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LEARNINGOBJECTIVES■ Understand ch
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One way to obtain more data would b
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TABLE 1.1 Basic definitions●●
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EXERCISE 1.2Reservoirs in the Earth
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EXERCISE 1.4Sources of Heat for Geo
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1.3 Units for Geologic MeasurementB
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FIGURE 1.5 Measuring the volume of
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FIGURE 1.6 The white cliffs of Dove
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MileFIGURE 1.7 Methods for dealing
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FIGURE 1.8 An example of the princi
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EXERCISE 1.9Name:Course:How Long Do
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APPENDIX 1.1Metric-U.S. Customary C
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LEARNINGOBJECTIVES■■Become fami
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plate between two continents, conti
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FIGURE 2.4 The Earth’s major clim
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More clues soon came from seismolog
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FIGURE 2.8 Magnetic reversals of th
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FIGURE 2.11 Rates of motion of the
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EXERCISE 2.7A Tale of Two RidgesNam
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EXERCISE 2.8Continental Rifting: Sp
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Even without any earthquake informa
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EXERCISE 2.10Estimating the Amount
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2.5.5 Hot Spots and Hot-Spot Tracks
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EXERCISE 2.11Name:Course:Determinin
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EXERCISE 2.12Name:Course:Long-Term
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GEOTOURS EXERCISE 2Analyzing Plate
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LEARNINGOBJECTIVES■ Understand wh
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When a mineral grows without interf
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FIGURE 3.1 Specimens of the mineral
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3.4.5 HardnessThe hardness of a min
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FIGURE 3.4 Crystals of some common
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FIGURE 3.6 Cleavage in common miner
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3.4.9 MagnetismA few minerals are a
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EXERCISE 3.7Identifying MineralsNam
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The minerals and elements we most r
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EXERCISE 3.9Mineral Resources in Yo
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GEOTOURS EXERCISE 3Extracting Miner
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APPENDIX 3.1Mineral Identification
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APPENDIX 3.2Determinative Tables fo
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APPENDIX 3.2Determinative Tables fo
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APPENDIX 3.3Common Minerals and The
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MINERAL PROFILE DATA SHEET NameSamp
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LEARNINGOBJECTIVES■■Understand
Page 107 and 108: FIGURE 4.1 The rock cycle.Heating a
Page 109 and 110: FIGURE 4.3 Typical grain shapes.(a)
Page 111 and 112: EXERCISE 4.2Describing a Rock’s T
Page 113 and 114: EXERCISE 4.3Understanding the Origi
Page 115 and 116: EXERCISE 4.4Interpreting the Textur
Page 117 and 118: ■ Hardness: Use a steel safety pi
Page 119 and 120: FIGURE 4.6 Flowchart for determinin
Page 121 and 122: 4.8 The Economic Value of RocksMost
Page 123 and 124: FIGURE 4.7 Examples of igneous, sed
Page 125 and 126: GEOTOURS EXERCISE 4Deciphering Land
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Page 129 and 130: crystalline rocks. Those that are s
Page 131 and 132: EXERCISE 5.3Interpreting Igneous Co
Page 133 and 134: FIGURE 5.4 Volcanic glasscontains n
Page 135 and 136: EXERCISE 5.5Interpreting Fragmental
Page 137 and 138: Felsic igneous rocks (from feldspar
Page 139 and 140: minerals melt, and (3) how plate-te
Page 141 and 142: EXERCISE 5.8Insights from Melting a
Page 143 and 144: EXERCISE 5.9Explaining Features of
Page 145 and 146: extreme crustal stretching has expo
Page 147 and 148: EXERCISE 5.13Interpreting Plate-Tec
Page 149 and 150: FIGURE 5.12 Distribution of volcano
Page 151 and 152: FIGURE 5.14 Comparison of areas in
Page 153 and 154: EXERCISE 5.15Stratovolcano Disaster
Page 155 and 156: GEOTOURS EXERCISE 5Exploring the Na
Page 157: IGNEOUS ROCKS STUDY SHEET NameSampl
Page 161 and 162: FIGURE 6.2 Chemical weathering of f
Page 163 and 164: FIGURE 6.3 The five steps in clasti
Page 165 and 166: 6.3.2 Chemical Sedimentary RocksChe
Page 167 and 168: 6.3.3 Biochemical and Organic Sedim
Page 169 and 170: TABLE 6.2 Classification of common
Page 171 and 172: FIGURE 6.5 Flow chart for identifyi
Page 173 and 174: FIGURE 6.6 Sediment sorting.(a) Poo
Page 175 and 176: EXERCISE 6.7Recognizing Sediment De
Page 177 and 178: FIGURE 6.9 Sedimentary rock beds.(a
Page 179 and 180: FIGURE 6.12 Cross bedding, a type o
Page 181 and 182: FIGURE 6.15 Fossils reveal remarkab
Page 183 and 184: FIGURE 6.16 Examples of depositiona
Page 185 and 186: EXERCISE 6.10Interpreting Sedimenta
Page 187 and 188: SampleTexture(grain size, shape,sor
Page 189 and 190: LEARNINGOBJECTIVES■■Understand
Page 191 and 192: FIGURE 7.1 Examples of changes from
Page 193 and 194: FIGURE 7.2 Growth of metamorphic mi
Page 195 and 196: FIGURE 7.3 Types of stress.(a) Comp
Page 197 and 198: FIGURE 7.5 Photomicrographs of rock
Page 199 and 200: FIGURE 7.6 Varieties of gneiss form
Page 201 and 202: EXERCISE 7.2Identifying Metamorphic
Page 203 and 204: FIGURE 7.11 Settings of metamorphis
Page 205 and 206: EXERCISE 7.4Interpreting the Type o
Page 207 and 208: EXERCISE 7.5Name:Course:Index Miner
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Sample Minerals presentMETAMORPHIC
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Sample Minerals presentMETAMORPHIC
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LEARNINGOBJECTIVES■■Become fami
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EXERCISE 8.1Which Image Works Best?
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More sophisticated grid systems are
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EXERCISE 8.2The Latitude/Longitude
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EXERCISE 8.3Locating Points with th
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EXERCISE 8.4Locating Points with th
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But which north is north? No, this
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e300FIGURE 8.10 An area in eastern
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8.4 Vertical Exaggeration:A Matter
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GEOTOURS EXERCISE 8Locating Places
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LEARNINGOBJECTIVES■ Understand ho
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this information on the most recent
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FIGURE 9.5 Digital elevation model(
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250300300FIGURE 9.7 Hachured contou
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9.3.4 Rules and Applications of Con
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EXERCISE 9.6Name:Course:Survival of
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FIGURE 9.8 Map of the microwave tow
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FIGURE 9.11 The effect of vertical
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GEOTOURS EXERCISE 9Working with Top
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APPENDIX 9.1Topographic Map Symbols
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Interpreting GeologicStructures on
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of structures on the ground (the ma
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EXERCISE 10.2The Basic Types of Con
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EXERCISE 10.3Determining Strike and
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FIGURE 10.4 Block diagrams.Map view
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FIGURE 10.6 Block diagrams showing
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FIGURE 10.7 Hanging wall, footwall,
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is not the same as that of the beds
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EXERCISE 10.9Name:Course:Interpreti
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FIGURE 10.9 Geologic maps (continue
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EXERCISE 10.11Name:Course:Using Sym
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EXERCISE 10.12Name:Course:Construct
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EXERCISE 10.13Interpreting Simple G
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FIGURE 10.13 Structural control of
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10.6 Reading Real Geologic MapsYou
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FIGURE 10.14 (continued).Geologic M
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EXERCISE 10.18Making a Geologic Map
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GEOTOURS EXERCISE 10Name:Course:Und
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LEARNINGOBJECTIVES■■Understand
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S-waves (FIG. 11.2b) are seismic wa
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FIGURE 11.4 Worldwide distribution
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FIGURE 11.5 Travel-time curves show
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EXERCISE 11.4Name:Course:Locating a
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EXERCISE 11.4Locating an Earthquake
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EXERCISE 11.4Name:Course:Locating a
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EXERCISE 11.5Name:Course:Determinin
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11.5 Predicting EarthquakeHazards:
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EXERCISE 11.7Locating Liquefaction
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After watching dramatic images of t
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APPENDIX 11.1Seismic Analysis Works
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LEARNINGOBJECTIVES■■Determine t
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EXERCISE 12.2Relative Ages in Cross
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EXERCISE 12.3Applying the Principle
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EXERCISE 12.4Name:Course:Using Sedi
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FIGURE 12.6 How the three kinds of
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EXERCISE 12.5Name:Course:Decipherin
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becoming extinct. When we find an i
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EXERCISE 12.6Name:Course:Dating Roc
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FIGURE 12.9 Changing parent:daughte
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EXERCISE 12.7Putting It All Togethe
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EXERCISE 12.8What Numerical Ages Ca
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EXERCISE 12.9Correlation (continued
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EXERCISE 12.10Cretaceous Paleogeogr
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Landscapes Formed13by StreamsStream
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EXERCISE 13.1Differences between St
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EXERCISE 13.2Why Some Streams Meand
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RFIGURE 13.5 The Genesee River sout
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EXERCISE 13.2Why Some Streams Meand
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FIGURE 13.8 A floodplain and its as
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ST. FRANCIS CO4070797064UNION PACIF
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1000Big900900B I G H I L LARKANSAS9
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FIGURE 13.13 Major drainage basins
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anchWTJ54MurphyNew BloomfieldTown65
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EXERCISE 13.6Recognizing Stages of
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MT T L E62446267DogRock757266170634
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13.7 When Streams Don’t Seemto Fo
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EXERCISE 13.7Deducing the History o
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13.8 When There’s Too Much Water:
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EXERCISE 13.9Estimating Potential F
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13.9 Streams, Society, and the Envi
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Groundwater as aLandscape Formerand
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EXERCISE 14.1Factors Affecting Infi
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EXERCISE 14.1Name:Course:Factors Af
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FIGURE 14.2 Groundwater landscape e
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60075000750600FIGURE 14.4 Karst top
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FIGURE 14.5 The water table separat
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EXERCISE 14.4Effects of a Changing
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100100100FIGURE 14.9 Karst topograp
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4400B a l d r i d g e C a n y o n42
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EXERCISE 14.7Name:Course:Environmen
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EXERCISE 14.8Name:Course:Environmen
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Glacial Landscapes15These jagged mo
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FIGURE 15.2 Mountain and continenta
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EXERCISE 15.1Comparison of Glaciers
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EXERCISE 15.3Erosional Features of
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15.3.2 Depositional LandscapesLands
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EXERCISE 15.4Landforms at the Termi
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900900800BOWEN1000700C R E E K900RO
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450400LEMON400ROADSLAYTON4504503Spo
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15.4 Landscapes Producedby Mountain
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The base level for a tributary stre
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3700380036003900Northwest BasinLake
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FIGURE 15.17 Atmospheric temperatur
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GEOTOURS EXERCISE 15Flowing Ice as
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GRID: 10/inch = 39,4/10cm
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Processes and Landforms16in Arid En
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FIGURE 16.2 Types of arid regions.(
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16.2 Processes in Arid RegionsNow l
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16.3 Progressive Evolution of Arid
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EXERCISE 16.3Interpreting Arid Land
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EXERCISE 16.3Interpreting Arid Land
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RiverGila85WatermanWashR A I N B O
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85130011001000FIGURE 16.8 Topograph
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FIGURE 16.10 Characteristics and ev
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400040004000L o w e V a l l e y4100
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FIGURE 16.13 Vulnerability to deser
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Shoreline Landscapes17Coastlines co
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FIGURE 17.1 Types of shorelines.(a)
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EXERCISE 17.1Erodibility and Stabil
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17.2.5 Emergent and Submergent Shor
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1382427FIGURE 17.5 Maine coastline
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EXERCISE 17.5Measuring Sea-Level (a
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FIGURE 17.7 Area just south of Lake
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17.3.2 Coastal Erosion and Depositi
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FIGURE 17.11 Erosional features of
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EXERCISE 17.7Erosional Processes an
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17.3.5 Depositional FeaturesPromine
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EXERCISE 17.9Depositional Processes
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FIGURE 17.18 The shoreline of theno
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FIGURE 17.21 Aerial view showing ho
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EXERCISE 17.10Name:Course:Unintende
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FIGURE 17.24 Counterclockwise wind
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EXERCISE 17.11Name:Course:Effects o
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FIGURE 17.27 Flooding caused by hur
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EXERCISE 17.12Effects of Storm Path
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GEOTOURS EXERCISE 17Understanding T
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LEARNINGOBJECTIVES■ Explain why p
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EXERCISE 18.1Humans and Earth Syste
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EXERCISE 18.2Short-Term Changes in
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Weather describes atmospheric condi
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FIGURE 18.5 The greenhouse effect.G
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EXERCISE 18.3Name:Course:Assessing
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FIGURE 18.8 Movement of water from
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FIGURE 18.10 Projected sea-level sc
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EXERCISE 18.4Effects of Sea-Level R
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FIGURE 18.13 Estimated human popula
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FIGURE 18.14 Two bird species hunte
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EXERCISE 18.6Name:Course:How Quickl
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GEOTOURS EXERCISE 18Inducing Change
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Courtesy of Allan Ludman; p. 162 (t
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270 280260240 250290 300Clay310 320
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Align with northern latitude tick m
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Laboratory Manual for Introductory Geology 4e

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