Ocean Deposits

Q.Describe the characteristics of different types of pelagic deposits (10/15 ). Q.Write short note on oceanic deposits (10/15). Q.Write short note: pelagic deposits ( 20/04) Q.Discuss the different bases for classifying the ocean deposits and give a detailed    account of pelagic deposits of the ocean.(60/07)

It refers to unconsolidated sediments derived from various sources deposited at the seafloor.

TYPES(Based on sources)

1.Terrigenous Materials

1. Gravel
2. Sand  
3. Silt  
4. Clay  
5. Mud: Murray divided it into 3 based on color
1. Blue Mud:Includes the materials derived from the disintegration of Rock rich in iron sulphide and organic matter. Predominantly present in Atlantic Ocean, Mediterranean sea and Arctic sea.
2. Red mud:Includes material derived from rocks rich in iron oxides;confined mostly to yellow sea, brazilian coast and floors of the Atlantic Ocean.
3. Green mud: It is formed from the Blue mud due to chemical weathering upon reaction of seawater .Contains green silicates of potassium and glauconite Found along the Atlantic and Pacific coast of North America of the coast of Japan

2. volcanic Materials

3. Organic Materials

1. Neritic matter:Includes skeletons of marine organisms and plant remains.Deposited mostly on the continental shelf and are generally covered by terrigenous materials.
2. Pelagic matter : It consists of matter derived from algae and are mostly in the form of liquid mud known as ooze.
1. Calcareous oozes:Contains lime content in abundance;rarely found at greater because because of their high degree of solubility.
1. Pteropod oozes:derived from floating pteropod called molluscs;contain 90% of calcium carbonate;found over Island features of the bottom, ridges, abyssal Hills, guyot,etc
2. Globigerina oozes:Derived from germ called globigerina;contains 20% calcium carbonate; temperate and tropical zones of atlantic ocean;Dominant in the reasons of mixing zone of cold and warm current mostly;.

2. Siliceous oozes:Silica content in abundance. Found at greater depth due to less solubility.
1. Radiolarian oozes: Derived from shells of radiolaria and foraminifera;covers largest area of pacific ocean;Concentration greatest along the equator.
2. Diatom oozes:Derived from shells of very microscopic plants;around antarctica and belt between alaska to japan.

4.Inorganic Materials:Basically precipitates which fall down from above also transported from the land by various agencies .

1. Red Clay:

• Previously, considered to be of organic origin
• Important member of pelagic deposits
• Silicates of  alumina and oxides of iron ore are  chief constituents.
• Red colour is due to ferrous oxide
• accounts for 36% of total Ocean deposits
• widely distributed at the greatest depth in all the oceans Covering trenches and ancient beds of the ocean
• they contain mostly ancient deposits

2. Meteoric Dust

CLASSIFICATION

(1) On the basis of location,

(2) On the basis of depth,

(3) On the basis of the origin of sediments etc

(1) On the basis of location(Sir John Murray)

(A) Pelagic deposits:(Deep ocean Floor)

(1) Red clay,
(2) Radiolarian ooze,
(3) Diatom ooze,
(4) Globigerina ooze, and
(5) Pteropod ooze.

(B) Terrigenous deposits:(continental shelf and slope)
(1) Blue mud,
(2) Red mud,
(3) Green mud,
(4) Coral mud,
(5) Volcanic mud,

(6) Gravel, and
(7) Sand.

2. On the Basis of Depth(Jenkins Classification)

(A) Deep sea deposits (Below 100 fathoms):

(a) Pelagic Deposits:

(1) Red clay,

(2) Radiolarian ooze,

(3) Diatom ooze,

(4) Globigerina ooze, and

(5) Pteropod ooze.

(b) Terrigenous Deposits:

(1) Blue mud,

(2) Red mud,

(3) Green mud,

(4) Coral mud, and

(5) Volcanic mud.

(B) Shallow sea deposits (between low tide water and 100 fathoms):

(1) Gravels,

(2) Sands, and

(3) Mud.

(C) Littoral deposits (Between high and low tide water):

(1) Gravels,

(2) Sands,

(3) Mud.

3. Classification on the Basis of Origin of Sediments:

(1) Littoral deposits (derived from land)):

(i) Shore deposits.

(ii) Shelf deposits.

(2) Hemipelagic deposits (Partly from land and partly from marine origin):

(i) Green mud.

(ii) Volcanic mud.

(iii) Coral mud.

(3) Eupelagic deposits (Of marine and cosmic origin):

(i) Red clay.

(ii) Radiolarian ooze.

(iii) Globigerina ooze.

(iv) Pteropod ooze.