Three Types of Ocean Floor Sediments

Marine Sediment Classification

Ocean floor sediments fall into three main categories by origin:

1. Lithogenous (Terrigenous) Sediments

• Source: Weathered rock/minerals from land.
• Transport: Rivers, wind (dust), ice (glacial flour), gravity (turbidity currents).
• Types: Quartz sand, clay (smectite, illite), rock fragments.
• Dominant on: Continental margins, shelves, abyssal plains near continents.

2. Biogenous Sediments

• Source: Skeletal remains of marine organisms.
• Calcareous: Foraminifera, coccolithophores, pteropods (CaCO₃). Form calcareous ooze above CCD (carbonate compensation depth ~4,500 m).
• Siliceous: Diatoms, radiolarians (SiO₂). Form siliceous ooze in high-productivity zones (equatorial upwelling, Southern Ocean).
• Dominant in: Pelagic (open ocean) settings away from land input.

3. Hydrogenous (Authigenic) Sediments

• Source: Chemical precipitation from seawater.
• Types: Manganese nodules, Fe-Mn crusts, phosphorites, metal sulfides (hydrothermal), evaporites (halite, gypsum).
• Form where: Slow lithogenous/biogenous accumulation (nodules), hydrothermal vents, restricted basins.

Minor Category: Cosmogenous

Extraterrestrial dust (micrometeorites) – trace but ubiquitous.

Sediment type reveals paleoceanography, climate history, and resource potential (nodules, phosphorites).