Chapter 9 Summary & Key Term Check
Chapter 9 Main Ideas
9.1 Clastic Sedimentary Rocks
Clastic sedimentary rocks are formed from rock and mineral particles that are cemented together. The naming system for these rocks depends on grain size, sorting, composition, and shape. Five common types of clastic sedimentary rocks are conglomerate, breccia, sandstone, shale, and mudstone. Sandstones are further organized according to the abundance of fine particles they contain, and the composition of their sand-sized grains.
9.2 Chemical and Biochemical Sedimentary Rocks
Chemical and biochemical sedimentary rocks form from ions that were transported in solution, and then converted into minerals by chemical and/or biological processes. The most common biochemical rock, limestone, typically forms in shallow tropical marine environments, where biological activity is a very important factor. Chert and banded iron formations can be from deep-ocean environments. Evaporites form where the waters of lakes and inland seas become supersaturated due to evaporation.
Extra! Compare & Contrast
Do you know your clastic, chemical, and biochemical rocks well enough to be able to tell them apart? How would you distinguish each of the following rocks from each other?
Start by thinking about which general sedimentary rock type they are. When you have it figured out, click each link to check your answer.
9.3 Organic Sedimentary Rocks
Organic sedimentary rocks contain abundant organic carbon molecules (molecules with carbon-hydrogen bonds). An example is coal, which forms when dead plant material is preserved in stagnant swamp water, and later compressed and heated.
9.4 Depositional Environments and Sedimentary Basins
There is a wide range of depositional environments, both on land (including glaciers, lakes, and rivers) and in the ocean (including deltas, reefs, shelves, and the deep-ocean floor). In order to be preserved, sediments must accumulate in sedimentary basins, many of which form through plate-tectonic processes.
9.5 Sedimentary Structures and Fossils
Sedimentary rocks can have distinctive structures that are important in determining their depositional environments. Fossils are useful for determining the age of a rock, the depositional environment, and the climate at the time of deposition.
9.6 Groups, Formations, and Members
Sedimentary sequences are classified into formations so that they can be mapped easily and without confusion. Formations can be combined into groups, or broken down into members for more detail.
Key Term Check
What key term from Chapter 9 is each card describing? Turn the card to check your answer.