Marine sedimentation

Sediment can be consist of either mineral or fossil particles, and both types can be found in many places on the bottom of the sea.

Classification of marine sedimentation :-

The sedimentation can be subdivided on the basis of the size of the particles or on the basis of their mode of formation.

• The size of particles produced by the break down of rock ranges from enormous boulders to tiny grains of microscopic clay or even finer particles called colloids. From the largest to smallest particles common in sedimentation, there are gravel, sand, silt and clay. silt and clay particles are typically mixed together and form a deposits of mud. The most common sedimentary deposits in the ocean are mud and sand.

• Based on the formation , we can subdivided sediments into five categories –
  • Terrigenous sediments are fine and coarse grains that are produced by the weathering and erosion of rocks on land, typically sand and mud.
  • Biogenous sediments are fine and coarse grains that are derived from the hard parts of the organisms, such as shells and skeletal debris like lime and siliceous mud.
  • Hydrogenous sediment particles that are precipitated by chemical or biochemical reactions in seawater near the sea floor. Ex – manganese and phosphate nodules.
  • Volcanogenous sediment particles that are ejected from volcanoes like ash as an example.
  • Cosmogenous sediments are very tiny grains that originate from outer space and tend to be mixed into terrigenous and biogenic sediments.

Factors that controls sedimentation :-

Two of the most important factors that determines the nature of a sediment deposits are particle size distribution and energy conditions at the site of deposition.

Fine grained sediments denotes low-energy conditions while coarse sediments, high energy conditions.

• In most cases, a clear relationship exists between the average grain size and the strength or energy of bottom currents at the time that sediment is deposited. The average particle size of a deposit is proportional to the energy level present at the time of deposition.
• energy
  • Under high energy conditions, water swift and turbulent, keeping fine grains in suspension and resuspended to those particles that momentarily settled to the ocean floor. This constant agitation of the sea bottom separates small grains and transports them into quitter water, which typically is deeper than turbulent water. Thus a coarse sand is deposited under high energy conditions.
  • Under low energy conditions, water currents are weak and water is quiet, do not receive a supply of coarse grains. Because the weak currents can’t transport them to these sites here mud typically accumulates.