A brief overview about marine sediments

• Marine sediments contains clues/records of earth's history from origin.

• Marine sediments provides a variety of important resources.

• Marine sediments have a variety of origin.

What are marine sediments?

• They are eroded rock particles and fragments.
• They are transported to the ocean.
• Deposits by settling through water column.
• Oceanographers decipher earth history through studying sediments.

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Paleoceanography and marine sediments

Paleoceanography: The study of how ocean atmosphere, and land interactions have produced changes in ocean chemistry, circulation, biology and climate.
• Marine sediments provides clues to the past changes.

Marine sediments classification

They are classified based on origin:

• Lithogenous: derived from land.

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• Biogenous: derived from organisms.

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• Hydrogenous or Authigenic: derived from water.

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Due to ocean water precipitation or ion exchange between ocean water and sediments, hydrogenous sediment forms. Examples include metal sulfides, evaporites.

• Cosmogenous: derived from outer space.

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For today's post we will focus on lithigenous sediments. While other sediments will be explained further.

Lithogenous sediments:

• Eroded rock fragments from the land.
• Also called terrigenous.
• Reflect composition of rock from which its derived.
• Produced by Weathering ( breaking of rocks into smaller pieces).
• Small particles are eroded and transported.
• Carried to the ocean, stream, wind, glaciers, gravity.
• Greatest quantity around continental margins.

Lithogenous sediments transport:
Water, wind.
Lithogenous sediments;
• it shows the composition of rocks of which it was derived from.
• Coarser sediments closer to shore.
• Finer sediments farther from shore.
• Mainly minerals- Quartz(si02)

        **Grain size**

The grain size is proportional to energy of transportation and deposition.

Sediment texture:

• Grain size sorting: indicator of selectivity of transportation and deposition processes.

• Textural matural
increases maturity if
• clay content decreases
• sorting increases
• non-quartz minerals decreases
• Grains are more rounded (abraded)

Sediment Distribution

Neritic:
• Shallow-water deposits.
• Close to land.
• Dominantly deposited quickly.

Pelagic:
• Deeper-water deposits.
• Finer-grained sediments.
• Deposited slowly.

Neritic Lithogenous sediments

• Beach deposits:
Mainly wave-deposited quartz rich sand.

• Continental shelf deposits:
Relict sediments.

• Turbidite deposits:
Graded bedding.

• Glacial deposits:

• High latitude continental shelf.
• Currently forming ice rafting.

Pelagic deposits

• They are fine grained marine sediments, accumulated slowly on the deep ocean floor.
• Pelagic Lithogenous sediments are from:

• Volcanic ash (volcanic eruptions).
• Wind-blown dust.
• Fine grained material transported NY ocean currents.
  • Abyssal clay:
• At least 70% clay sized particles from continent.
• Red from oxidized iron (Fe).
• Abundant if other sediments are absent.

References

• Link

• Oxford geology dictionary