calcareous zone

8/3/2019 Calcareous Zone

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Ooze Formation

Deep ocean sediment containing at least 30%biogenic material is called ooze

Oozes are named after the dominant remnant

organism constituting them

When these organisms die, their shells settle

slowly toward the bottom, mix with finegrained terrigenous silts and clays, andaccumulate as ooze.



Tend to accumulate at depths above theCarbonate Compensation Depth (CCD) and is

generally absent below.

Calcareous ooze forms mainly from shells ofamoeba-like foraminifera, small drifting mollusks

called ptereopods, and tiny algae known ascoccolithophores.

When conditions are ideal, these organismsgenerate massive volumes of sediment.



Rate of Formation

Oozes accumulate slowly

Rate: ~ 1-6 cm (1/2 to 2 ½ inches) perthousand years.

Accumulation of any ooze depends on… A delicate balance between the abundance

of organisms at the surface

The rate at which they dissolve once theyreach the bottom

The rate of accumulation of terrigenoussediment.



Only a small proportion of calcareous ooze isprecipitated inorganically.

For the most part, calcareous ooze comprisesthe fossil hard parts of planktic and benthicsingle-celled marine organisms whose calciumcarbonate skeletons are discarded upon death

or reproduction.Generally white to pinkish-white in color

Calcareous ooze is distinguished by its main

biogenic component into:foraminiferal ooze (Animal)

coccolithophore ooze (Plant)

pteropod ooze (Animal)



Foraminiferal Ooze

Contains foraminifera·Divided into planktic (floating) and

benthic (bottom) foraminifera·

Inhabit upper few hundred meters andbottom of the world oceans·

Low number of modern species·

Vast quantities produce a sedimentcover that occupies ~ 1/3 earth’s

surface·

Utilized to interpret marine sediments



Coccolithophore Ooze

Contains coccolithophoridsBelong to marine nanno-phytoplankton (algae)

whose cells are covered by calcite platelets

Live in all oceans. Species dominance varies bygeographical zonation

Once dead, coccolithophorids disintegrate intosingle coccoliths that lastly are preserved as c-

oozeSmall in size but occur huge in numbers in the

sediment



Coccolithophores surround themselves with a microscopicplating made of limestone (calcite).These scales, known as coccoliths, are shaped likehubcaps and are only three one-thousandths of a millimeter

in diameter.



White Cliffs of Dover

• The remains of countless coccolithphores have been

compressed and lithified (transformed into stone) to form theimpressive White Cliffs of Dover in SE England.

• Though formed at moderate ocean depth about 100 millionyears ago, tectonic forces have uplifted Dover's chalk cliffs totheir present prominent position.



Pteropod Ooze

Contains pteropods (marine gastropod mollusksadapted to pelagic life that have a foot with wing-shaped lobes used as swimming organs)

Most species seem to prefer the circum-global tropical

and subtropical regions.Distribution limited by water depth, temperature,

salinity, oxygen content, and nutrient supply.

They form very thin and fragile shells that hardly

preserve under biochemical (i.e. dissolution) orphysical (i.e. ingestion) attack.

For this reason, preservation is mostly restricted toshallow parts of the oceans (i.e., continental shelf,

slopes, ridges and rises)



Clione limacinaClio pyramidata



Deep Sea Sediment Distribution

Type CompositionAtlantic

%

Pacific

%

Indian

%

Global

%

Foram.

Ooze

Calcium

Carbonate65 36 54 47

Pteropod

Ooze

Calcium

Carbonate2 0.1 - 0.5

DiatomOoze

Silica 7 10 20 12

Radiolarian

OozeSilica - 5 0.5 3

Red Clay

Aluminum

Silicate 26 49 25 38

Worldwide distribution of recent shelf sediments by composition isstrongly related to latitude and climate.

Calcareous biogenic sediments dominate tropical shelves



Global Distribution

The blue indicates areas of calcareous ooze coverage. (~48% of Seafloor)



http://geology.uprm.edu/

http://www.atmos.albany.edu/geology/

http://www.marinebio.net/marinescience

calcareous zone

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