Sedimentary Rock Classification Dana Desonie, Ph.D. Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required) To access a customizable version of this book, as well as other interactive content, visit www.ck12.org CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based collaborative model termed the FlexBook®, CK-12 intends to pioneer the generation and distribution of high-quality educational content that will serve both as core text as well as provide an adaptive environment for learning, powered through the FlexBook Platform®. Copyright © 2013 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws. Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution/NonCommercial/Share Alike 3.0 Unported (CC BY-NC-SA) License (http://creativecommons.org/licenses/by-nc-sa/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated herein by this reference. Complete terms can be found at http://www.ck12.org/terms. Printed: August 20, 2013 AUTHOR Dana Desonie, Ph.D. www.ck12.org C ONCEPT Concept 1. Sedimentary Rock Classification 1 Sedimentary Rock Classification • Describe how sedimentary rocks are classified. How do you know that this is a sedimentary rock? If you look closely at the rock you will see that it is made of sand-sized particles that have been lithified to create sandstone. The rock is eroding into very unique shapes, but these shapes are more likely to form from a rock made of small cemented together grains than from an igneous or metamorphic rock. Types of Sedimentary Rocks TABLE 1.1: Sedimentary rock sizes and features. Rock Conglomerate Breccia Sandstone Siltstone Shale Sediment Size Large Large Sand-sized Silt-sized, smaller than sand Clay-sized, smallest Other Features Rounded Angular When sediments settle out of calmer water, they form horizontal layers. One layer is deposited first, and another layer is deposited on top of it. So each layer is younger than the layer beneath it. When the sediments harden, the layers are preserved. Sedimentary rocks formed by the crystallization of chemical precipitates are called chemical sedimentary rocks. As discussed in the "Minerals" lessons, dissolved ions in fluids precipitate out of the fluid and settle out, just like the halite in Figure 1.1. 1 www.ck12.org FIGURE 1.1 The evaporite, halite, on a cobble from the Dead Sea, Israel. Biochemical sedimentary rocks form in the ocean or a salt lake. Living creatures remove ions, such as calcium, magnesium, and potassium, from the water to make shells or soft tissue. When the organism dies, it sinks to the ocean floor to become a biochemical sediment, which may then become compacted and cemented into solid rock (Figure 1.2). FIGURE 1.2 Fossils in a biochemical rock, limestone, in the Carmel Formation in Utah. Table 1.2 shows some common types of sedimentary rocks. 2 www.ck12.org Concept 1. Sedimentary Rock Classification TABLE 1.2: Common Sedimentary Rocks Picture Rock Name Conglomerate Type of Sedimentary Rock Clastic (fragments of non-organic sediments) Breccia Clastic Sandstone Clastic Siltstone Clastic Shale Clastic Rock Salt Chemical precipitate 3 www.ck12.org TABLE 1.2: (continued) Picture Rock Name Rock Gypsum Type of Sedimentary Rock Chemical precipitate Dolostone Chemical precipitate Limestone Bioclastic (sediments from organic materials, or plant or animal remains) Coal Organic Summary • Sediments settle out of water in horizontal layers. • Sedimentary rocks are classified based on how they form and on the size of the sediments, if they are clastic. • Clastic sedimentary rocks are formed from rock fragments, or clasts; chemical sedimentary rocks precipitate from fluids; and biochemical sedimentary rocks form as precipitation from living organisms. Practice Use this resource to answer the questions that follow. 4 www.ck12.org Concept 1. Sedimentary Rock Classification MEDIA Click image to the left for more content. 1. List the three types of sedimentary rocks. 2. List the characteristics of clastic rocks. 3. How do clastic rocks form? 4. Contrast conglomerates and breccia rocks. 5. What can be found in clastic rocks? 6. Explain the difference between layers and bands. 7. What can we learn from sedimentary rocks? 8. How do chemical rocks form? 9. What are bioclastic rocks? 10. List the two types of biocalstic rocks. Review 1. How does an organism become a sedimentary rock? 2. How do chemical sedimentary rocks differ from clastic sedimentary rocks? 3. What are the different sedimentary rock types based on grain size, from small to large? References 1. Mark A. Wilson (Wilson44691). . Public Domain 2. Mark A. Wilson (Wilson44691). Fossils in a biochemical rock, limestone, in the Carmel Formation in Utah. Public Domain 5
© Copyright 2024