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READING QUESTIONS: Sedimentary Rocks NAME________________________ GEOL 131 Winter 2017 DUE: Tuesday, January 31st 44 pts All answers should be in your own words. The Importance of Sedimentary Rocks (p. 68) 1. What sedimentary rock is used as an energy source? ______________ Origins of Sedimentary Rock (p. 69-70) 2. What is the first step in the formation of sedimentary rock? ______________________ 3. Give two examples of Earth surface features that transport sediment. (2 pts) a. __________________________ b. __________________________ 4. Which of the following is not a sediment deposit? (Circle one answer.) a. Mud suspended in a river current b. A river delta c. A sand dune d. A pile of gravel at the front of a glacier 5. For each description below, give the name of the sedimentary rock category that matches it. (3 pts) a. Carbon-rich remains of organisms: ____________________ b. Solid sediment (e.g. sand, mud): __________________ c. Sediment formed when ions precipitate from a solution: __________________ Detrital Sedimentary Rocks (p. 70-74) 6. What two minerals are the main components of detrital rocks? ____________________________ (2 pts) 7. If a body of the igneous rock granite were weathered into sediment, and the feldspar crystals from the granite were preserved in the resulting sedimentary rock, what would this indicate about the speed of erosion and deposition of the sediment, and why? (3 pts) _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 8. Detrital rocks are mainly distinguished on what basis? ___________________________________ 9. Describe the relationship between sediment particle size in detrital rocks and the amount of energy needed to transport the particles. (2 pts) _______________________________________________ _______________________________________________________________________________ 10. What is the difference between the detrital rocks conglomerate and breccia? __________________ _______________________________________________________________________________ 11. Why does the detrital rock shale often form barriers to the movement of groundwater? __________ ________________________________________________________________________________ 12. Match each type of sandstone with the correct description: (3 pts) a. graywacke made mostly or entirely of quartz grains _____ b. quartz sandstone contains significant feldspar _____ c. arkose contains significant rock fragments and clay matrix _____ 13. Which detrital rock, conglomerate or breccia, has sediment that likely underwent less transport, and how can you tell? (2 pts) _____________________________________________________________ __________________________________________________________________________________ Chemical Sedimentary Rocks (p. 74-78) 14. What is the difference between how inorganic and biochemical rocks form? (2 pts) _______________ __________________________________________________________________________________ __________________________________________________________________________________ 15. Match each chemical sedimentary rock to the correct description: (2 pts) a. Travertine biochemical; formed of shell fragments _____ b. Oolitic limestone biochemical; formed of microscopic plankton _____ c. Coquina inorganic; precipitated in caves _____ d. Chalk inorganic; forms around “seed particles” in shallow oceans _____ 16. EXTRA CREDIT: Oolitic limestone and sandstone can look very similar. What is one easy test you could perform to tell them apart? (1 pt) ______________________ 17. The chemical rock chert often forms in the same way as chalk, by compaction of millions of plankton skeletons on the ocean bottom. But their physical properties are very different. Name one important difference in their physical properties, and explain the cause of this difference. (2 pts) __________________________________________________________________________________ __________________________________________________________________________________ Coal: An Organic Sedimentary Rock (p. 78-79) 18. What has to accumulate in large quantities in order for coal to eventually form? __________________ 19. What special condition is required for the accumulation referred to in the last question to occur? __________________________________________________________________________________ Turning Sediment into Sedimentary Rock: Diagenesis and Lithification (p. 80-81) 20. Fill in the blanks in the following sentences using words from the list below. Not all words will be used. During ________________, new ___________________ crystals form between existing sediment grains. These crystals precipitate from ions dissolved in __________________, and fill in the ___________ spaces between grains. (2 pts) GROUNDWATER, SEDIMENT, ACIDIC, PORE, CEMENTATION, MINERAL Classification of Sedimentary Rocks (p. 81-82) 21. Sediment particle size is the main basis for classifying detrital rocks. What two characteristics are used to classify chemical rocks? (1 pt) a. _____________________________________ b. _____________________________________ 22. A chemical sedimentary rock consisting of fine-crystalline quartz and having a dark color would be called _________________. Sedimentary Rocks Represent Past Environments (p. 82-88) 23. Define sedimentary environment. (2 pts) _________________________________________________ __________________________________________________________________________________ 24. For each rock listed below, name one sedimentary environment in which it could have formed. (2 pts) Well-sorted sandstone: __________________________________ Fossil-rich limestone: __________________________________ Shale: __________________________________ Coquina: __________________________________ 25. Match each sedimentary structure to the correct description. (3 pts) a. Ripple marks Any trace of past life preserved in rock ______ b. Graded bed Inclined layers of sediment associated with sand dunes ______ c. Cross-bedding Formed when fine-grained sediment dries out ______ d. Strata Ridges formed at right angles to direction of current flow ______ e. Mud cracks Layers of sediment or sedimentary rock ______ f. Fossils Grain size decreases upward within a single layer ______ 26. The figure below shows a cross-section of a ripple mark. In which direction was the current flowing that created this structure (left or right)? (1 pt)