Curatorial Reference Pages

THROUGH THE CCD

The sequence of photomicrographs of smear slides below show a transect demonstrating typical sediments above, near and below the calcite compensation depth (CCD). Because calcite, aragonite and calcium carbonate are dissolved under conditions of high pressure and cold water, water depth is a major factor in determining the level of the CCD. Click on the photomicrographs to view larger images.

Above the CCD
SOUTH CENTRAL ATLANTIC
Water depth: 1959m
PPL
10ºS, 15ºW
Sample Ref: INMD-110BX
Courtesy: Paula Worstell, SIO

Foraminiferal ooze with pteropods
Description:
Abundant whole foraminifer tests (some opaque due to size and presence of air bubbles within test chambers), foraminifer fragments from larger foraminifera and pteropods comprised of calcium carbonate and aragonite indicate a sample from well above the CCD. Benthic foraminifera and sponge spicules are also present. The foraminifera are in the size range 0.05-0.10 mm.

Partway down to CCD
EASTERN NORTH PACIFIC
Water depth: 2845m
PPL
10ºN, 109ºW
Sample Ref: BNFC-44P, 1cm
Courtesy: Paula Worstell, SIO

Calcareous ooze
Description:
At deeper water depths the calcareous ooze consists mainly of fragmented foraminifera tests; complete foraminifera tests are rare. The sediment is still highly calcareous and larger fragments are in the size range 0.05-0.10 mm.

Apporaching the CCD
EASTERN NORTH PACIFIC
Water depth: 3891m
PPL
12ºN, 110ºW
Sample Ref: BNFC-53P, 6cm
Courtesy: Paula Worstell, SIO

Clayey calcareous ooze
Description:
At water depths approaching the CCD, foraminifers are mostly dissolved; only very small calcareous fragments remain. Siliceous microfossils are not dissolved. Fragments of siliceous radiolarians are present. The larger clumps are of the order of 0.05 mm in size.

Below the CCD
NORTH PACIFIC, EAST OF HAWAII
Water depth: 5365m
PPL
27ºN, 147ºW
Sample Ref: ZETES-38G, 64cm
Courtesy: Paula Worstell

Deep sea red clay
Description:
Below the CCD calcium carbonate is dissolved. Although calcareous microfossils may be living in the water column, their tests are not preserved in sediments on the sea floor. Seen here is a barren, fine-grained clay. Reddish-brown grains and irregular flecks of iron oxides are present together with clay- and very fine silt- grade mineral particles. Individual grains are under 4 µm (0.004 mm) in size.

Below the CCD
NORTH CENTRAL PACIFIC
Water depth: 5530m
PPL
33ºN, 174ºW
Sample Ref: JYN-4G, 27cm
Courtesy: Paula Worstell, SIO

Deep sea red clay
Description:
Deposited below the CCD, this fine-grained deep-sea clay contains some diatoms and siliceous spicules. Because the calcareous components are dissolved, siliceous microfossils are often concentrated in sediments deposited below the CCD. Diatoms are in the size range 10-100 µm (0.01-0.1 mm) and individual clay grains are under 4 µm (0.004 mm) in size.

Rapid burial, below CCD
SW PACIFIC, SAMOAN PASSAGE
Water depth: 5763m
PPL
17ºs, 168ºW
Sample Ref: CATO-29PG, 25cm
Courtesy: Paula Worstell, SIO

Foraminifer nannofossil ooze
Description:
An unusual occurrence of a foraminifer nannofossil ooze recovered from well below the CCD. A turbidity current transported these calcareous sediments from a nearby topographic high. Rapid burial protected the calcareous microfossils from dissolution. The small planktonic foraminifers are in the size range of 0.05-0.10mm. Fragments of larger foraminifera are also present.

Comparison of the CCD in the Altantic and Pacific oceans
CENTRAL PACIFIC
Water depth: 5060m
PPL
23ºN, 153ºW
Sample Ref: HILO-7G, 5cm
Courtesy: Paula Worstell, SIO

Deep Sea Red Clay
Description:
The CCD in the Pacific Ocean lies between 4200-4500 meters. This barren fine-grained red clay was recovered at a water depth of 5060m, well below the CCD in the central Pacific. Reddish-brown grains and irregular flecks of iron oxides are present, together with clay- and very fine to fine silt-grade mineral particles. Large grains are about, or under, 0.01 mm in size.

NORTH ATLANTIC
Water depth: 5386m
PPL
11ºN, 34ºW
Sample Ref: INMD-BX, Top
Courtesy: Paula Worstell, SIO

Image available soon

Image available soon
Description:
The CCD in the Atlantic Ocean lies at or deeper than 5000 meters water depth. This calcareous foraminifer nannofossil ooze, recovered from a water depth of 5386m provides evidence of a more shallow CCD in the North Atlantic.

Other curatorial reference pages:

Accumulation rates

 Sediment classification
Pacific transect Grain identification
Atlas of sedimentary structures Miscellany

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