Marine Geology Marine Sediments errigenous and Pelagic The two main classifications of marine sediments are terrigenous and pelagic Terrigenous sediments are derived from land and found near shore Normally, the go from rivers to costal regions Pelagic sediments settle slowly out of the water column and are deposited all over the ocean Pelagic sediments are mostly associated with deep sea areas The further away from land the smaller the sediment size Terrigenous Terrigenous sediments are usually classified by their size Sediment grain size depends on the energy of the depositional environment, with more energy leading to larger grain sizes A steep mountain stream, where water flows quickly downhill, might have very large grain sizes, from gravel to pebbles A river bed, where currents are slower, might be filled with sand Beaches, where waves crash against the shore and the surf runs in and out, often have sandsized particles as well Farther offshore, where the water is less active, terrigenous materials will be smaller or clay size particles Pelagic Pelagic sediments are classified by composition, not size The size of pelagic sediments is uniformly pretty small There are four main compositional groups for marine sediment which are Lithogenous, Biogenous, Hydrogenous, and Cosmogenous Lithogenous - This is sediment that is derived from rocks Biogenous - This is sediment that is derived from living organisms Hydrogenous - This sediment is derived from the ions in seawater Cosmogenous -The Earth is continually being bombarded from space by meteors and cosmic dust