Which type of sediment is formed from chemical reactions in seawater?

Hydrogenous sediments are formed from chemical reactions that take place in seawater. These sediments consist of materials precipitated directly from seawater, often as a result of processes such as evaporation or changes in temperature and pressure. For example, minerals like manganese nodules or evaporites can form when elements in seawater become supersaturated and precipitate out.

This distinguishes hydrogenous sediments from other types. Terrigenous sediments originate from land erosion and are transported to the ocean. Biogenic sediments are derived from the accumulation of biological materials, often from organisms such as foraminifera or diatoms. Pelagic sediments refers to sediments that settle in the open ocean, consisting of both biogenic and hydrogenous materials but not specifically tied to chemical processes alone. Thus, the categorization of hydrogenous sediments highlights their unique formation through direct chemical reactions in the seawater.