Sedimentology - Sedimentary Rock Types

Sedimentary Rock Types

There are four primary types of sedimentary rocks: clastics, carbonates, evaporites, and chemical.

• Clastic rocks are composed of particles derived from the weathering and erosion of precursor rocks and consist primarily of fragmental material. Clastic rocks are classified according to their predominant grain size and their composition. In the past, the term "Clastic Sedimentary Rocks" were used to describe silica-rich clastic sedimentary rocks, however there have been cases of clastic carbonate rocks. The more appropriate term is siliciclastic sedimentary rocks.
  • Organic sedimentary rocks are important deposits formed from the accumulation of biological detritus, and form coal and oil shale deposits, and are typically found within basins of clastic sedimentary rocks
• Carbonates are composed of various carbonate minerals (most often calcium carbonate (CaCO₃)) precipitated by a variety of organic and inorganic processes. Typically, the majority of carbonate rocks are composed of reef material.
• Evaporites are formed through the evaporation of water at the Earth's surface and most commonly include halite or gypsum.
• Chemical sedimentary rocks, including some carbonates, are deposited by precipitation of minerals from aqueous solution. These include jaspilite and chert.