Catalog - Globorotalia africana

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Globorotalia africana

Citation: Globorotalia africana El Naggar 1966

Type sample (& lithostrat): upper Owaina Shale.

Type age (chronostrat): Upper Paleocene, Globorotalia aequa/Globorotalia esnaensis Subzone of the Globorotalia velascoensis Zone

Type locality: From approximately 156.5 meters above the base of the Gebel Owaina section (ca. 27°45' N., 32°45.75' E.), about 12 km. north of the Nile at El Mahamid, Esna-Idfu region , Upper Egypt.

"Diagnosis.- A Globorotalia with small, concavo-convex, compressed test, spinose surface; small, globular, raised early chambers and compressed lenticular later ones; very large test chamber; acute axial periphery and partially developed pseudo-keel. "Description.- Test small, compressed and coiled in a low trochospire; dorsal side gently convex with the early chambers slightly raised above the circumambient last whorl; ventral side gently concave although the chambers are inflated; equatorial periphery ovoid, elongate, distinctly lobate and spinose; axial periphery acute with a partially developed pseudo-keel on the last chamber; on the dorsal side the chambers are 16, arranged in 3 dextrally coiled whorls; the initial chambers increase slowly in size, are extremely small, globular, inflated, almost indistinct, and are followed by relatively larger, globular, inflated chambers which increase moderately in size; the last whorl is composed of 6 relatively large chambers which are globular in the early part, becoming gradually more compressed towards the last chamber, which is roughly lenticular, slightly inflated, and compressed; sutures on the dorsal side short, very gently curved to almost straight, depressed; on the ventral side they are relatively long, straight, radial and strongly incised; umbilicus small, shallow and open; aperture interiomarginal, extraumbilical-umbilical, a low arch with a small, delicate lip; wall calcareous, perforate; surface delicately spinose especially along the periphery.

Maximum diameter 0.30 mm.; minimum diameter 0.20 mm.; thickness of last chamber 0.14 mm.

Remarks. - Globorotalia africana El-Naggar is distinguished from the closely related G. sibaiya El-Naggar by its concavo-convex test, numerous chambers, acute axial periphery, partially developed pseudo-keel, raised, globular early chambers and compressed lenticular later ones.
The only known Paleocene Globorotalia species with a gently curved plane of coiling along which the test grows in such a way as to produce a shallow concavo-convex form, is Globorotalia kilabiyaensis El-Naggar from the underlying Danian rocks. This species may represent the ancestral stock from which G. africana evolved, although G. kilabiyaensis was not recorded from rocks younger than Upper Danian, while G. africana was only recorded from the uppermost Paleocene."

References:

El-Naggar, Z. R. (1966). El-Naggar, Z. R. (1966). Stratigraphy and planktonic foraminifera of the Upper Cretaceous-Lower Tertiary succession in the Esna-Idfu region, Nile Valley, Egypt, U. A. R. Bulletin of the British Museum (Natural History) Geology. supplement 2: 1-291. Bulletin of the British Museum (Natural History). supplement 2: 1-291. gs

Guasti, E. & Speijer, R. P. (2008). Guasti, E. & Speijer, R. P. (2008). Acarinina multicamerata n. sp. (Foraminifera): a new marker for the Paleocene-Eocene thermal maximum. Journal of Micropalaeontology. 27: 5-12. Journal of Micropalaeontology. 27: 5-12. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia africana El Naggar 1966

Globorotalia africana

References:

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