- \r\n \t
- Explain the differences between the four kinds of sedimentary rocks: clastic, chemical, biochemical, and organic.<\/li>\r\n \t
- Describe some of the specific kinds of rocks in each of the four categories, and the depositional environments in which they form.<\/li>\r\n \t
- Describe the various terrestrial and marine sedimentary depositional environments, and explain how the formation of sedimentary basins is related to plate tectonic processes.<\/li>\r\n \t
- Apply your understanding of the features of sedimentary rocks, including grain characteristics, sedimentary structures, and fossils, to the interpretation of past depositional environments and climates.<\/li>\r\n \t
- Explain what groups, formations, and members are in sedimentary rocks, and why such terminology is used.<\/li>\r\n<\/ul>\r\n
Earth's Storybook<\/h1>\r\nAll three kinds of rocks\u2014igneous, metamorphic, and sedimentary\u2014can tell us parts of Earth\u2019s story. It is sedimentary rocks, however, that are most akin to a geological storybook. They form one layer at a time, capturing information about conditions at Earth\u2019s surface within each layer. The layers stack one on top of another, forming a chronological sequence like pages in a book.\r\n
Sedimentary Rocks Form From the Products of Weathering and Erosion<\/h1>\r\nWeathering and erosion (Chapter 8) are the first two steps in the transformation of pre-existing rocks into sedimentary rocks. The remaining steps in the formation of sedimentary rocks are transportation, deposition, burial, and lithification. These steps are shown on the right-hand side of the rock cycle diagram below (Figure 9.2).\r\n\r\n[caption id=\"attachment_300\" align=\"aligncenter\" width=\"583\"]
![\"\"](\"https:\/\/opentextbc.ca\/kzlab\/wp-content\/uploads\/sites\/360\/2021\/08\/The-rock-cycle.png\")
Figure 9.2<\/strong> The rock cycle. Processes related to sedimentary rocks are shown on the right-hand side. Source: Steven Earle (2015), CC BY 4.0. Image source.<\/a>[\/caption]\r\n\r\nTransportation<\/strong> is the movement of sediments or dissolved ions from the site of erosion to a site of deposition. This can be by wind, flowing water, glacial ice, or mass movement down a slope. Deposition<\/strong> takes place where the conditions change enough so that the sediments can no longer be transported. This could happen if the current slows down.\r\n\r\nBurial<\/strong> occurs when sediments are deposited upon existing sediments, covering and compacting them. Lithification<\/strong> is what happens\u00a0when those compacted sediments become cemented together to form solid sedimentary rock. Lithification occurs at depths of hundreds to thousands of metres within Earth.\r\nFour Types of Sedimentary Rocks<\/h1>\r\nSedimentary rocks can be divided into four main types: clastic<\/strong>, chemical<\/strong>, biochemical<\/strong>, and organic<\/strong>. Clastic<\/strong> sedimentary rocks are composed mainly of material that is transported as solid fragments (called clasts), and then cemented together by minerals that precipitated from solution. Chemical sedimentary rocks are composed mainly of material that is transported as ions in solution. Biochemical<\/strong> sedimentary rocks also form from ions in solution, but organisms play an important role in converting those ions into calcium carbonate or silica body parts. Organic<\/strong> sedimentary rocks contain large amounts of organic matter, such as from plant leaves and tree bark.\r\n
\r\n\r\nConcept Check: Sedimentary Rock Types<\/strong>\r\n\r\n[h5p id=\"99\"]\r\n\r\n<\/div>","rendered":"![\"\"](\"https:\/\/opentextbc.ca\/kzlab\/wp-content\/uploads\/sites\/360\/2018\/08\/Drumheller-roadside-1024x768.jpg\")
Figure 9.1<\/strong> Cretaceous sedimentary rocks exposed along a road near Drumheller, Alberta, Canada. Sedimentary rocks form in layers called beds, and the planar boundaries that separate each bed are called contacts. Each bed tells a story about the conditions in which it formed. In this picture the beds are indicating that sea level repeatedly rose and fell. The black layer about halfway up the picture is a coal seam. It tells us that the environment at that time was swampy. Source: Karla Panchuk (2008), CC BY 4.0.<\/figcaption><\/figure>\n Chapter Goals<\/h1>\n
Complete this chapter so you can:<\/p>\n
- \n
- Explain the differences between the four kinds of sedimentary rocks: clastic, chemical, biochemical, and organic.<\/li>\n
- Describe some of the specific kinds of rocks in each of the four categories, and the depositional environments in which they form.<\/li>\n
- Describe the various terrestrial and marine sedimentary depositional environments, and explain how the formation of sedimentary basins is related to plate tectonic processes.<\/li>\n
- Apply your understanding of the features of sedimentary rocks, including grain characteristics, sedimentary structures, and fossils, to the interpretation of past depositional environments and climates.<\/li>\n
- Explain what groups, formations, and members are in sedimentary rocks, and why such terminology is used.<\/li>\n<\/ul>\n
Earth’s Storybook<\/h1>\n
All three kinds of rocks\u2014igneous, metamorphic, and sedimentary\u2014can tell us parts of Earth\u2019s story. It is sedimentary rocks, however, that are most akin to a geological storybook. They form one layer at a time, capturing information about conditions at Earth\u2019s surface within each layer. The layers stack one on top of another, forming a chronological sequence like pages in a book.<\/p>\n
Sedimentary Rocks Form From the Products of Weathering and Erosion<\/h1>\n
Weathering and erosion (Chapter 8) are the first two steps in the transformation of pre-existing rocks into sedimentary rocks. The remaining steps in the formation of sedimentary rocks are transportation, deposition, burial, and lithification. These steps are shown on the right-hand side of the rock cycle diagram below (Figure 9.2).<\/p>\n
Figure 9.2<\/strong> The rock cycle. Processes related to sedimentary rocks are shown on the right-hand side. Source: Steven Earle (2015), CC BY 4.0. Image source.<\/a><\/figcaption><\/figure>\n Transportation<\/strong> is the movement of sediments or dissolved ions from the site of erosion to a site of deposition. This can be by wind, flowing water, glacial ice, or mass movement down a slope. Deposition<\/strong> takes place where the conditions change enough so that the sediments can no longer be transported. This could happen if the current slows down.<\/p>\n
Burial<\/strong> occurs when sediments are deposited upon existing sediments, covering and compacting them. Lithification<\/strong> is what happens\u00a0when those compacted sediments become cemented together to form solid sedimentary rock. Lithification occurs at depths of hundreds to thousands of metres within Earth.<\/p>\n
Four Types of Sedimentary Rocks<\/h1>\n
Sedimentary rocks can be divided into four main types: clastic<\/strong>, chemical<\/strong>, biochemical<\/strong>, and organic<\/strong>. Clastic<\/strong> sedimentary rocks are composed mainly of material that is transported as solid fragments (called clasts), and then cemented together by minerals that precipitated from solution. Chemical sedimentary rocks are composed mainly of material that is transported as ions in solution. Biochemical<\/strong> sedimentary rocks also form from ions in solution, but organisms play an important role in converting those ions into calcium carbonate or silica body parts. Organic<\/strong> sedimentary rocks contain large amounts of organic matter, such as from plant leaves and tree bark.<\/p>\n
\nConcept Check: Sedimentary Rock Types<\/strong><\/p>\n
\n
![\"\"](\"https:\/\/opentextbc.ca\/geology\/wp-content\/uploads\/sites\/110\/2015\/06\/The-rock-cycle.png\")