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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 48 (1964)

Issue: 4. (April)

First Page: 516

Last Page: 517

Title: Distribution and Morphological Variations of Living Planktonic Foraminifers: ABSTRACT

Author(s): Allan W. H. BE, William H. Hamlin

Article Type: Meeting abstract


Surface (0-10m) and vertical (300-0m) plankton samples were collected at seventy stations (116 samples) in the North Atlantic during the summer of 1962. Three faunal provinces were recognized. The subarctic fauna consisted of Globigerina bulloides, G. quinqueloba, and G. pachyderma. The subtropical fauna was typified by Globigerinoides ruber and G. sacculifer. The subarctic-temperate boundary was crossed five times in the western half of the northern traverse from New York to Scotland. The temperate fauna was dominated by

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Globorotalia inflata (d'Orbigny) but also included subarctic or subtropical species. Highest foraminiferal concentrations were found in the temperate-subarctic zone, and the lowest in the central Sargasso Sea.

Bathythermograph temperatures ranged from 4.4°C. to 27.5°C. Temperature inversions occurred at nine stations SE. of Newfoundland. Within the BT range (0-274 m) temperatures fluctuated from 2.2°C. to 10.6°C. Surface salinities varied from 32.58 ^pmil in cold water to 37.59 ^pmil in warm water.

Morphological variations resulting from environmental influences were evident in some species. The maximum diameter of Globigerina bulloides was generally less than 0.4 mm above 14°C. Large specimens (0.6+mm) and specimens with the aperture over four chambers were abundant below 12°C. and when the salinity was less than 35.5 ^pmil. Deeper-water samples from stations having temperature inversions contained abundant forms with a reduced final chamber, similar to Globigerina quadrilata Galloway and Wissler. The terminal chamber in some specimens had a secondary aperture.

Globigerina cf. quinqueloba, common in waters below 15°C., graded into G. pachyderma with decreasing temperature. Typical G. pachyderma was not found in surface tows. Although encountered rarely, it did appear when water temperatures were below 10°C.

Globorotalia inflata was abundant between 13.5°C. and 18°C. Only deep-water tows with temperatures about 10°C. contained small forms with thick tests, a reduced final chamber, and an aberrant aperture.

The signal morphological variation was observed from the deepest tow taken (0-1150 m), and contained forms transitional between common Hastigerina pelagica and large, digitate Hastigerinella rhumbleri.

That depth and temperature greatly influence the distribution as well as the morphology of planktonic foraminifers is evident.

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