Final answer:
Sedimentary rocks are classified as clastic, formed from particles like sand, silt, and clay, chemical, formed from precipitates like rock salt, and biochemical, formed from organic material like calcium carbonate shells.
Step-by-step explanation:
The three classifications of sedimentary rocks are clastic, chemical, and biochemical. Clastic sedimentary rocks are formed from weathered fragments of other rocks, which are transported and deposited in layers, often with a predominant composition of quartz due to its stable nature and resistance to abrasion. Grain size, such as sand, silt, and clay, in clastic rocks indicates the mode of transportation and deposition of the sediment. Chemical sedimentary rocks are formed through the precipitation of minerals from water, examples include rock salt and gypsum. Finally, biochemical sedimentary rocks are formed from the accumulation of organic material and can include deposits from organisms like foraminifera, which leave behind calcium carbonate shells.
Understanding how sedimentary rocks form assists geologists in inferring past environments and climates. Recognition of sediment size within clastic rocks provides clues on sediment transport mechanisms, while the formation process of non-clastic rocks reveals insights about past water chemistry.