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Geosciences LibreTexts

3.1: Sources and types of marine sediment

There are four kinds of marine sediments, Lithogenous, biogenous, hydrogenous and cosmogenous. Lithogenous are from the land, they form through the weathering process and are composed of small particles from weathered rock and volcanic activity. And within Lithogenous sediments there are two sub categories: Terrigenous and red clay. Terrigenous sediments are produced when the weathering process occurs above water. Wind and other natural sources then carry these particles to the ocean where they sink. Red clay, also known as abyssal clay however, is mostly located in the ocean and is formed from a combination of terrigenous material and volcanic ash. In terms of size, terrigenous particles are generally larger than abyssal clay particles so they sink faster.

 Biogenous sediments are formed from the remnants of organisms that refused to be dissolved. Good examples of these organisms include shellfish, clams, anything that has a shell. Other things that could avoid being dissolved include bones and teeth and other appendages. In deeper waters, shells of plankton and other microscopic organisms form these kinds of sediments. Hydrogenous sediments are sediments solidified out of ocean water. As such, chemical reactions create these kinds of sediments. The precipitation of dissolved chemicals from seawater. These kinds of sediments are found commonly near hydrothermal vents. Cosmogenous sediments are probably the most interesting of all four kinds of sediment because they are alien in nature. These kinds of sediments are carried to earth on meteorites or asteroids. They are usually a conglomeration of different kinds of metals and due to their nature, are not easy to find. 




Sedimentary rocks are made of sediments. In general, sediments occurred when the organic or inorganic material are broken down by processes of watering and erosion. There are four types of sediment: cosmogenous (from outer space), volcanogenous (ash from volcanic eruptions), terrigenous (continents erosion and river runoff), and biogenous (skeletons of marine creatures). Sediments are classified according to their size. In order to define them from the smallest size to the largest size: clay, silt, sand, pebble, cobble, and boulder. According to the video that I found online, named "Sediments: Definition, Type & Feature" by Dr Rebecca Gillaspy, delves deeper into the three types of sediments: clastic, biogenic, and chemical that forms sedimentary rocks. Sediment rocks, generally formed from the compaction and cementation of sediments are known as the rock capable of containing fossils. clastic sedimentary rocks are the compacted sediments and are composed of silicate minerals, for example, shale and sandstone. Biochemical sedimentary rocks are the products of organisms who used materials dissolved in water to build their tissue, for example, corals, radiolaria, and diatoms. Chemical sedimentary rocks are form when mineral constituents in solution become supersaturated and inorganically precipitate, for example, oolitic limestone, barite, and gypsum. As we mention earlier, sedimentary rocks are the only type of rocks that may contain fossils. In the other words, they contains the evidence of past life.