DOMINANT SEDIMENTS TYPE IN ROCK Loose fragments of rocks or minerals broken off of bedrock Mineral crystals that precipitate directly out of water

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1 LAST NAME (ALL IN CAPS): FIRST NAME: 7. SEDIMENTARY PROCESSES, ROCKS, AND ENVIRONMENTS Instructions: Refer to Laboratory 6 in your Lab Book on pages to answer the questions in this work sheet. Your work will be graded on the basis of its accuracy, completion, clarity, neatness, legibility, and correct spelling of scientific terms. If you want to test a mineral for effervescence and want to apply HCl, you must first ask permission from your instructor (remember HCl is an acid and is hazardous to health). Some rocks and minerals that you would be working with may have sharp edges and corners, therefore, be careful when working with them! When you are done with your lab work, please clean the desk and leave all materials you worked with in the same way you found them! INTRODUCTION Sedimentary Rock: form when sediments are compressed and cemented together. Sediments are loose grains and chemical residues of Earth materials, including rock fragments, mineral grains, and parts of plants or animals like seashells and twigs. DOMINANT SEDIMENTS TYPE IN ROCK Loose fragments of rocks or minerals broken off of bedrock Mineral crystals that precipitate directly out of water Shells (fossils) SEDIMENTARY ROCK CLASS Detrital Chemical Biochemical WENTWORTH SIZE SCALE OF DETRITAL SEDIMENTS Gravel: > 2 mm (2 mm = 0.2 cm) { 1cm = 10mm} Sand: 1/16 to 2 mm (feels gritty) {1/16 = } Mud: < 1/16 mm {silt and clay} DESCRIPTION OF DETRITAL SEDIMENT SIZE TERMS Sand This is the size range of grains in a sandbox. The grains are visible and feel gritty when rubbed between your fingers. Silt: Grains too small to see but you can feel them as very tiny gritty grains when you rub them between your fingers or teeth. Clay: Grains too small to see, feel like chalk dust when rubbed between your fingers or teeth. DEFINITION SORTING: Refers to the degree of similarity of sediment size. If sediments have nearly same size, they are said to be well sorted; if they are mixtures of different sizes, they are poorly sorted. ENVIRONMENTS IN WHICH SEDIMENTS & SEDIMENTARY ROCKS ARE FORMED (FIG 6.10 IN LAB MANUAL) Sediments are deposited in many different environments. Each environment has characteristic sediments, sedimentary structures, and organisms that can become fossils. The information gained from grain characteristics, sedimentary structures, and fossils can be used to infer ancient environments (paleo-environments). Important: Most sedimentary rocks are cemented by the mineral calcite. Applying hydrochloric acid (HCl) on many sedimentary rocks can show fizzing due to the presence of some calcite in the rock. So, fizzing of a sedimentary rock doesn t necessarily make that rock a limestone! Page 1 of 5

2 PALEOENVIRONMENTS OF SOME SEDIMENTARY ROCKS SEDIMENTARY ROCK DETRITAL ROCKS Conglomerate Breccia Sandstone Mudstone CHEMICAL ROCKS Limestone Chert Travertine Rock salt, gypsum, dolomite BIOCHEMICAL ROCKS Fossiliferous limestone Lignite, Coal ENVIRONMENT OF FORMATION (PALEOENVIRONMENT) Glacial, Stream (land) Glacial, Stream (land) Stream, Sand dunes, Beach (land); Base of continental slope (sea) Marsh, Floodplain (land) Deep sea Deep sea Evaporating (hot) springs (land) Evaporating playa lake/lagoon (land) Continental shelf (sea) Peat bog (land) tropical climate QUESTIONS Q1. (I) What specific type of biochemical limestone is shown in Fig. 6.6B (Lab Manual)? Refer to Figure 6.9 (Lab Manual) for names and descriptions of sedimentary rocks. Type of biochemical limestone: (II) Explain how you determined this name. Q2. (I) What is the roundness of the clasts in the figure given on page 176 (Lab Manual)? Roundness: (II) Explain how and in what environment the shell clasts could have attained their roundness. Refer to Figure 6.10 for a diagram showing the environments in which various types of sediments may be formed and later modified. Q3. Analyze the sedimentary rocks given on page 171 (Lab Manual). For each picture, describe the rock s composition (what it is made of), and texture (the size, shape, and arrangement of its parts). ROCK # ROCK S COMPOSITION & TEXTURE Page 2 of 5

3 Q4. Refer to images of volcanic rocks and sediments from around Mount Rainier, WA, on page 172 (Lab Manual). Mount Rainier is a volcano that belongs to the Cascade Range on the West Coast! Note how the sediment changes from A to D. Image A was taken from near the top of the volcano Image B was taken near the middle of the volcano s slope Image C was taken in a River that drains away from the base of the volcano Image D was taken 30 km downstream, at a delta (i) What is the Wentworth size class of each grain of the sediment at each location? (ii) What is the grain roundness at each of the following locations? (iii) In general, would you classify the sediments in each image as detrital, biochemical, or chemical? (iv) Name the kind of rock that the sediment in each image would form if it became lithified (Fig. 6.9, step 3) (v) Based (i) and (ii) above, describe what happens to detrital sediment with distance from its source. Q5. SEDIMENT ANALYSIS, CLASSIFICATION, AND INTERPRETATION. SAMPLE A (vi) Describe how and in what environment (Figure 6.10) this sediment may have formed. Page 3 of 5

4 SAMPLE B (vi) Describe how and in what environment (Figure 6.10) this sediment may have formed. Hint: the sediments are all quartz SAMPLE C (vi) Describe how and in what environment (Figure 6.10) this sediment may have formed. Page 4 of 5

5 Q6 Obtain six sedimentary rock samples from your instructor. Analyze them and for each sample complete a line on the given Sedimentary Rocks Worksheet using the steps to classify a sedimentary rock given in Figure 6.9 (page 164, Lab Manual). SEDIMENTARY ROCKS WORKSHEET SAMPLE # COMPOSITION (Fig. 6.2, 6.9): (DETRITAL, BIOCHEMICAL, CHEMICAL) TEXTURAL & OTHER DISTINCTIVE PROPERTIES (Figs. 6.3, 6.9): (ANGULAR/ROUNDED; GRAVEL/SAND/MUD; LAYERED; EFFERVESCES, ETC.) ROCK NAME (Fig.6.9) S-1 S-7 S-9 (Example) S-11 S-12 S-14 Page 5 of 5