Lithification is the process by which sediments are turned into solid rock. It occurs entirely within the early stage of diagenesis, which is the physical and chemical changes that affect sediments after their deposition. Other words that overlap with lithification are induration, consolidation, and petrifaction. Lithification is most closely related to rock formation because it involves the transformation of loose grains of sediment into coherent and hard rock.
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How Does Lithification Work?
Lithification works by reducing the pore space between sediment particles and replacing it with solid mineral material. The main processes involved in lithification are compaction and cementation.
Compaction
Compaction involves squeezing the sediment into a smaller volume by packing the sediment particles more closely, by removing water from the pore space (desiccation) or by pressure solution at the points where sediment grains contact each other. Compaction reduces the porosity and permeability of the sediment, making it more dense and rigid.
Cementation
Cementation involves filling pore space with solid minerals (usually calcite or quartz) that are deposited from solution or that enable existing sediment grains to grow into the pores. Cementation binds the sediment particles together, making them more cohesive and strong.
What Types of Rocks are Formed by Lithification?
Lithification can produce different types of rocks depending on the nature and composition of the original sediment. The most common types of rocks formed by lithification are sedimentary rocks, such as sandstone, shale, limestone, and conglomerate. Sedimentary rocks are classified based on the size, shape, and sorting of their sediment particles, as well as their mineralogy and texture.
Some examples of sedimentary rocks formed by lithification are:
- Sandstone: a clastic rock composed of sand-sized grains cemented by quartz or calcite.
- Shale: a clastic rock composed of clay-sized grains compacted into thin layers.
- Limestone: a chemical or biochemical rock composed of calcite derived from shells, corals, or other organic sources.
- Conglomerate: a clastic rock composed of rounded pebbles or cobbles cemented by quartz or calcite.
Why is Lithification Important?
Lithification is important because it preserves the history and characteristics of the original sediment in the form of rock. Lithified rocks can provide valuable information about the environment and conditions in which they were deposited, such as climate, water depth, current direction, biological activity, and tectonic activity. Lithified rocks can also serve as reservoirs for natural resources such as oil, gas, water, and minerals.
According to Britannica, lithification is a complex process whereby freshly deposited loose grains of sediment are converted into rock. Lithification may occur at the time a sediment is deposited or later. According to Dictionary.com, lithification is most closely related to rock formation because it involves the transformation of loose grains of sediment into coherent and hard rock.
