PHYS-106A+Lab+7+Sedimentary+Rocks+2022 2

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Saginaw Valley State University *

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106A

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Geology

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Dec 6, 2023

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docx

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4

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Laboratory Exercise 7: Sedimentary Rocks PHYS-106A, Physical Geology Student Name: ___________ Student Learning Outcomes : - Identify observable properties of sedimentary rocks - Demonstrate knowledge of sedimentary rock properties by identifying sedimentary rocks from short videos Introduction Chapter 7 of Exploring Geology, 6 th Edition , states that sedimentary rocks form by lithification of loose sediments or precipitation of crystals from solution. We can generally identify sedimentary rocks by their clasts/grain sizes and texture. Clasts and grains can be used interchangeably to describe the pieces that make up clastic sedimentary rocks. Part 1: Definitions Using Chapter 7, write definitions of the following terms in the space provided. Term Definition Clastic sedimentary rock Chemical/Nonclasti c sedimentary rock Facies Sedimentary environment Clasts Sorting Transgression Chemical precipitation 1
Part 2: Sedimentary Rock Identification Use the basic physical properties of sedimentary rocks from Chapter 7 in the textbook and the attached sedimentary rock classification chart to identify the rock in each video linked in the Canvas assignment page. Some properties are hard to see in the videos or can help you ID unknowns, so I’ve filled them in for you. Remember, carbonate rocks like limestone or those with lots of calcite shell fragments effervesce with HCl. Sample ID (Video #) Clastic or Chemical/Nonclastic ? Texture Composition Sorting (Poorly = lots of grain size variation. Well = grains are mostly the same size) Additional information Rock Name (Very coarse, coarse, medium, fine, very fine, or microcrystalline for some chemical sedimentary rocks) List mineral(s) present like calcite, quartz, clay minerals; also if fossils present (use Classification Chart below) Very poorly, poorly, moderately, well, or very well, for clastic only 1 -- 2 Effervesces with HCl acid 3 Effervesces with HCl acid 4 -- 5 -- 6 Contains sulfate 7 -- 8 Effervesces with HCl acid 2
9 -- 10 -- 11 Effervesces with HCl acid 12 -- Sedimentary Rock Classification Chart All the sedimentary rocks we use in this lab are in this table; use it to identify the samples in the videos. Since these are all the rocks you will see in lab, it’s smart to look them up online to view their properties and see more examples of them! Classification Composition Color (specific to the rock samples in this lab) Texture Sorting (variation in grain sizes) Rock Name Clastic Calcite, quartz + mostly angular shell fragments Tan/brown/white Coarse to Very Coarse Moderately to Poorly Coquina Quartz, calcite Many colors possible due to variety of grains Coarse to Very Coarse Moderately to Poorly Conglomerate Clay minerals (flattened appearance) Dark gray to black Fine Well to Very Well Shale Clay minerals, quartz silt, can have fossils Gray to dark gray Fine Well to Very Well Mudstone Quartz Tan to brown Fine to medium Moderately to Well Sandstone Chemical/Nonclastic Halite Clear Microcrystalline Does Not Apply Halite Iron oxide - Hematite Dark reddish Fine Hematite Calcite – large shell Tan to Gray, lighter shell fragments Fine to Coarse (shell fragments are Fossiliferous limestone 3
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fragments in calcite matrix coarse) Calcite Tan to Gray Fine Limestone Calcite, banded with calcite + mud Reddish-tan with white bands of calcite Fine Travertine Gypsum (calcium sulfate) Mostly White with a few reddish/gray inclusions Fine Gypsum Dolomite, dark mud sediment Very dark gray to black, some white areas. Fine to medium Dolostone Part 3: Closing Questions If your classification of rocks 8, 1, and 5 is incorrect in Part 2, I will grade this section based on the classification of the rock you named for each of those rock samples. 1. What is the likely environment of formation of sedimentary rock 8 , and why did you conclude this? 2. What is the likely environment of formation of sedimentary rock 1 , and why did you conclude this? 3. How did sedimentary rock 5 form, and in what sedimentary environment might we find it? 4