Types of Marine Sediments

Marine sediments are critical components of Earth’s oceans, representing the accumulation of various materials over geological time. These sediments serve as essential archives of Earth’s history, revealing past climatic, oceanographic, and geologic conditions. Understanding the different types of marine sediments is vital for scientists and researchers to gain insights into past environmental changes and ongoing geological processes.

Terrigenous Sediments

Terrigenous sediments constitute the most extensive and diverse type of marine sediments. They originate from land-based sources and are transported to the ocean by various means, such as rivers, wind, and glaciers. The composition of terrigenous sediments varies widely depending on the geology of the source area. Common components include clay, silt, sand, and organic matter.

Examples:

• The Amazon River discharges vast amounts of terrigenous sediments into the Atlantic Ocean, forming the world’s largest submarine fan.
• The Mississippi River contributes substantial terrigenous sediment loads to the Gulf of Mexico.

Biogenic (Organic) Sediments

Biogenic sediments are primarily composed of the remains of marine organisms. These sediments form due to the accumulation of shells, skeletons, and other hard parts of marine organisms. The calcium carbonate shells of foraminifera, coccolithophores, and mollusks, as well as the silica-based skeletons of diatoms, are common constituents of biogenic sediments.

Examples:

• The White Cliffs of Dover in the UK are composed of biogenic sediments formed by the accumulation of coccolithophores over millions of years.
• Diatomaceous earth, composed of fossilized diatoms, is used in various industrial applications.

Hydrogenous (Chemical) Sediments

Hydrogenous sediments are formed through chemical processes in the water column or at the seafloor. These sediments result from the precipitation of minerals directly from seawater or the alteration of pre-existing minerals by chemical reactions. Common hydrogenous sediments include manganese nodules, evaporites, and phosphorites.

Examples:

• Manganese nodules, rich in manganese, iron, and other metals, are found in deep-sea areas like the Pacific Ocean’s abyssal plains.
• Evaporites, such as gypsum and halite, form in shallow marine environments with high evaporation rates, like the Persian Gulf.

Cosmogenous Sediments

Cosmogenous sediments originate from extraterrestrial sources, primarily meteoroids and cosmic dust. These sediments are relatively rare in comparison to other types and are mostly found in oceanic areas far from the continents. They provide insights into the history of extraterrestrial impacts on Earth.

Examples:

• Microtektites, tiny glassy particles formed from the intense heat of meteoroid impacts, are found in deep-sea sediments globally.
• Iridium anomalies in sediments, linked to the asteroid impact that caused the Cretaceous-Paleogene mass extinction, offer crucial evidence for understanding this significant event.

Volcanogenic Sediments

Volcanogenic sediments result from volcanic activities both on the seafloor and adjacent land areas. Volcanic eruptions release lava, ash, and other volcanic debris, which eventually settle in the ocean. Volcanic islands and seamounts contribute substantial amounts of these sediments.

Examples:

• The Hawaiian Islands contribute volcanic ash and debris, forming distinct layers in the surrounding marine sediments.
• The eruption of Mount St. Helens in 1980 led to the deposition of volcanic sediment in nearby marine environments, impacting local marine life.

The following table represents key data for Major Types of Marine Sediments

The study of marine sediments provides valuable insights into Earth’s history, climate changes, and geological processes. Each type of marine sediment plays a unique role in shaping our understanding of the planet’s past and present.