Marine Sediments Review

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Microscopic algea= coccolithophores

-When calcareous ooze lithifies= chalk

Other minor component= corlas, snails, sea urchins, starfish, other algae

c) Hydrogenous sediments

-Derived from chemical retains in seawater or from interations between and ocean sediments.

• Examples:

- Manganese nodules

Manganese oxide ( MnO2) and iron Oxided

-whery low rate of accumulation ,

origin unknown

• Evaporites

-Mineral precipitation after seawaterevaporates

- Near edgeds of the ocean

- Phosphates, Carbonates, Metal sulfides

d) Cosmogenous sediments

-In significant portion of overall ocean sediments

Found in deep ocean where other sediments accurate very slowly.

Origin from farce = extraterrestrial fragments,-

III) Classified by location

Neritic deposits

Located on continental margin and around iskabd

-Determined by terrigeneous material

-Rarely composed of biogeneous sediments

• Examples of neritic terrigenous sediments:

-Beach sane= quart rich

-Glacial deposits

-Turbidity deposities

----> graded bedding; coarser material at the base and smaller parcels at the top

• Examples of neritic biogenous sediments:

-Modern carbonate deposits (limestone): in shallow, warm oceans and around tropical islands= coral reefs, ovoid shoals.

Pelagic deposits

• Pelagic lithogenic sediments:

- Pelagic biogenous sediments:

- Siliceous ooze:

- Calcareous ooze

2) Controls on sediment accumulation

• Example: biogenous sediment

• Accumulation and distribution depends on:

Studies of sediment deposition use Sediment Traps.

A Few Study Questions:

• What are the major mechanisms that bring terrigenous materials to the ocean?

• What is a turbidite deposit? How does it form? What is graded bedding?

• Are abyssal clays, diatomaceous earth, glacial deposits, volcanogenic particles, rock and gravel ALL terrigenous sediment types?

• What are the different kinds of biogenous sediments?

• Some cyanobacteria can form massive calcium carbonate structures that were very abundant in the past (between 1 and 3 billion years ago). Presently, these deposits are found in hypersaline, mid-latitude environments. What are these structures called?

• Where are manganese nodules found in the ocean floor?

• How are hydrogenous sediments formed?

• Why are siliceous deposits most abundant under regions of upwelling?

• Are neritic deposits rich in biogenous sediments? Why?

• Define the calcite compensation depth (CCD).

• What physico-chemical conditions affect the dissolution of CaCO3 in the deep ocean?

• What mechanisms help in increasing the sediment rate of particles?