Oceanography Chapter 4

saliceous ooze covers

14% of the ocean floor

Two significant sources of calcium carbonate biogenous ooze are

1: Foraminifers 2: Coccolithophores aka (Nannoplankton)

Conditions below the CCD

1: Lower Temperature 2: Higher Pressure 3: High CO2 4: Low PH

The distribution of biogenous sediment on the ocean floor depends on 3 fundamental processes:

1: Productivity 2: Destruction 3: Dilution

Stromatolites

1: are lobate structures consisting of fine layers of carbonate that form in specific warm shallow water environments such as the high salinity tidal pools in Shark Bay Australia. 2: Cyanobacteria produce these deposits by trapping fine sediment in mucous mats.

Biogenous ooze

1: biogenous ooze must contain at least 30% biogenous material by weight. often the other 70% is composed of lithogenous clay. 2: Chief contributors to biogenous sediment are algea and protozoans. Mostly found in Pelagic areas, rarely neritic. Distribution dependent on: 1) productivity 2) Dilution 3) Destruction

Destruction:

1: occurs when skeletal remains dissolve in seawater at depth. 2: In some cases biogenous sediment dissolves before ever reaching the sea floor.

Dilution

1: occurs when the deposition of other sediments decreases the percentage of the biogenous test material below the 30% necessary to classify it as ooze. 2: Occurs most often because of the abundance of corse grained material in neurotic environments. 3: so biogenous oozes are uncommon along the continental margins.

Radiolarians

1: single celled protozoans. Most are planktonic. 2: " Living snowflakes of the sea " 3: Also contribute to siliceous ooze

Diatoms

1: unicellular algae that have a unique glass-like wall ( greenhouse) made of silica. 2: Because they photosynthesize they need strong sunlight and are found only within the upper sunlit surface waters of the ocean. 3: Primarily free floating or PLANKTONIC (Wandering)

Ancient Marine Carbonate deposits constitute:

2% of earths crust and 25% of all sedimentary rocks on earth.

Cakcareous ooze contains at least

30% of the hard remains of calcareous secreting organisms.

CCD

Calcite Compensation Depth Calcium Carbonate Compensation Depth Carbonate Compensation Depth

When diatoms lithify ( harden) on the ocean floor it becomes

Diatomaceous Earth

Areas of high productivity

Many silica tests sinking Silica tests accumulate a siliceous ooze above abyssal clay.

Hydrated form of silica is (SiO2) and is called

Opal

Microscopic Organisms

Produce tiny shells called tests (Testa=shell) These begin to sink after they die and continually rain down in great numbers onto the deep ocean floor. This Creates deposits called (OOZE) similar to toothpaste consistency.

Biogenous Sediment

Rare in marine environment especially in the deep water where fewer organisms live.

Calcium Carbonate dissolves more readily in cold water as opposed to warm water. It also dissolves at higher pressure. In warmers shallower parts of the ocean seawater is generally saturated with calcium carbonate so calcite does not dissolve. In the deep ocean pressure is greater and the water is colder and contains more carbon dioxide which forms carbonic acid. These 3 things speed the dissolution of calcium carbonate.

The depth where calcium carbonate readily dissolves is cal the lyso (to break, Loosening) cline ( Slope) *LYSOCLINE*

Biogenous Sediment Composition

Two most common chemical compounds: Calcium carbonate (CaCO3) and Silica (SiO2) Hydrated form of silica is (SiO2)

Foraminifers (Forams)

are single celled protozoans many of which are planktonic. The DO NOT photosynthesizes they must Ingest other organisms for food. They produce hard calcium carbonate shells in which the organism lives.

Pelagic Deposits

common on the deep floor because there is so little lithogenous sediment deposited at great distances from the continents that could dilute the biogenous material.

Carbonate minerals:

contain CO3 in their chemical formula. such as Calcium Carbonate CaCO3. Calcium carbonate is primarily limestone.

Imestone

contain fossil marine shells suggesting biogenous origin while others appear to have formed directly from seawater without the help of any marine organism.

Siliceous Ooze

contains at least 30% of the hard remains of silica secreting organisms.

Biogenous Sediment

derived from the remains of hard parts of once-living organisms.

Areas of low productivity

few silica tests sinking, silica tests dissolved before making ooze

Calcareous ooze

is comprised of mainly shells of foraminifers, coccoliths, and other calcareous secreting organisms.

Microscopic sediment

is more abundant

Biogenous sediment

is one of the most common types of pelagic deposits

Productivity

is the number of organisms present in the surface water above the ocean floor. Surface waters with high biologic productivity contain many living and reproducing organisms which are conditions likely to produce biogenous sediments. Surface waters with low biologic productivity contain too few organisms to produce biogenous oozes on the ocean floor.

Calcite

only accumulates near tops of tall peaks that rise off the sea floor and extend above the CCD but dissolve at deeper depths associated with the base of peaks. Creates marine equivalent of a " Snow Line"

Diatoms

produce oxygen

When diatoms die

their tests (shells) contain droplets of oil that accumulate on the sea floor and are the beginning of petroleum deposits.

When coccolithophores die

they accumulate on the ocean floor and it forms white deposits called CHALK.