OCNG 251: Chapter 4 Part 2

What is the average depth of CCD?

*4500 m*; also depends on the chemistry of the ocean, so some parts are as deep as 6000 m or as shallow as 3500 m

What is foraminifera?

-heterotrophic -planktonic or benthic -found everywhere in the ocean -different water temperatures affect the chemistry of the shells

What is distribution of neritic and pelagic sediments controlled by?

-proximity to sources of lithogenous sediments -productivity of microscopic marine organisms -depth of water -sea floor features

What are some resources obtained from ocean sediments?

-sand & gravel -evaporative salts -energy resources -manganese nodules

Calcareous ooze

-warm, shallow ocean is saturated with calcium carbonate -however, cool, deep ocean is undersaturated with calcium carbonate

What 3 factors affect the distribution of biogenous ooze?

1. *productivity*: number of organisms present in the surface waters 2. *destruction*: dissolution 3. *dilution*: deposition of other sediments decreases relative %

Neritic sediments cover what fraction of the sea floor?

1/4 (25%)

Pelagic sediments cover what fraction of the sea floor?

3/4 (75%)

What is the average depth of lysocline?

4000 m

Modern calcareous oozes are rare below what depth?

5000 m; they can only exist below CCD if buried

Biogenic oozes can contain up to what percent non-biogenic components?

70%

Most biogenic sediments consist of tiny shells called microfossils that are made of what two substances?

CaCO3 & SiO2

The calcite compensation depth (CCD) is the depth in the ocean where ______ equals _____?

carbonate dissolution; carbonate supply

Where is biogenous ooze common?

deep sea floor because so little lithogenous sediment is deposited

Calcite compensation depth (CCD)

depth where CaCO3 accumulation=dissolution; below this depth, dissolution>accumulation

On the whole, what is the most important mechanism of transporting continental-margin lithogenous sediments?

flowing water

Calcareous ooze must contain at least 30% of what?

hard parts from calcareous organisms such as: coccolith ooze, formanifera ooze, Globigerina ooze, pteropod ooze, and ostracod ooze

What are coccolithophores?

single-celled planktonic algae, depends on photosynthesis -produce thin plates to produce a spherical test; when they die, plates disaggregate & accumulate on the seafloor as ooze -ooze lithifies to form chalk; EX: white cliffs of Dover

Lysocline

the depth at which CaCO3 begins to dissolve rapidly