Catalog - Globigerina ouachitaensis gnaucki

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Globigerina ouachitaensis gnaucki

Citation: Globigerina ouachitaensis gnaucki Blow & Banner 1962

Type specimens: Plate IX L-N; P44509

Type sample (& lithostrat): sample FCRMI965,

Type age (chronostrat): Upper Eocene, or Oligocene

Type locality: Lindi area, Tanzania

The fairly small test consists of about three whorls of subglobular to slightly ovoid, inflated chambers arranged four to four and a half in each whorl in a moderately high trochospire. The rate of enlargement of the chambers increases during ontogeny; in dorsal aspect the early chambers are of semi-circular outline, being distinctly longer circumferentially than they are broad radially, but in the last whorl the chambers broaden more rapidly than they lengthen and become slightly ovoid in axial profile. The sutures are distinctly and broadly depressed; the dorsal intercameral sutures are initially curved but become nearly radial. The spiral suture and the equatorial periphery are strongly lobulate. The axial periphery is broadly rounded. The umbilicus is fairly broad, open and deep and even in four-chambered forms loses the square outline typical of Globigerina ouachitaensis ouachitaensis. The apertural face is less flattened than in G. ouachitaensis ouachitaensis and consequently the umbilicus is less clearly delimited from the rest of the ventral surface. The intraumbilical aperture is a fairly low arch, highest at its anterior end, bordered by a distinct rim. Relict apertures of the last two or three chambers are visible within the umbilicus. The wall is fairly thin, uniformly and finely perforate; its surface is cancellate and hispid. The hispidity is strongest on the earlier parts of the test, being reduced on the last chamber where the apertural face is smooth.

Maximum diameter of holotype: 0·36 nm1;

This subspecies is named for F. R. Gnauck, Palynologist, The British Petroleum Co. Ltd, in recognition of his help with the photographs (Plates XVI and XVII).

Remarks; This form differs from Globigerina ouachitaensis ouachitaensis in its loss of a quadrate umbilicus and symmetrical aperture, and in its acquisition of a changed growth rate and a distinctly more hispid test. It differs from G. ouachitaensis ciperoensis in having a higher-spired test with fewer chambers per whorl, a more strongly developed apertural rim, more rapidly enlarging chambers and a more hispid test. It differs from G. praebulloides praebulloides in having more, less rapidly enlarging chambers per whorl, a smaller aperture, and a more hispid test.

Stratigraphical range: Globigerina ouachitaensis gnaucki ranges from the G. turritilina turritilina Zone, Upper Eocene, to the G. oligocaenica Zone, Oligocene, in the Lindi area. It has not been seen in any Aquitanian sediments either in Europe or the Caribbean region.

References:

Blow, W. H. & Banner, F. T. (1962). The mid-Tertiary (Upper Eocene to Aquitanian) Globigerinaceae. In, Eames, F. E., Banner, F. T., Blow, W. H. & Clarke, W. J. (eds) Fundamentals of mid-Tertiary Stratigraphical Correlation. Cambridge University Press, Cambridge 61-151. gs

Blow, W. H. (1969). Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In, Bronnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967. E J Brill, Leiden 380-381. gs

Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (2006a). Taxonomy, biostratigraphy, and phylogeny of Eocene Globigerina, Globoturborotalita, Subbotina, and Turborotalita. In, Pearson, P. N., Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 41(Chap 6): 111-168. gs V O

Pearson, P. N. & Wade, B. S. (2015). Systematic taxonomy of exceptionally well-preserved planktonic foraminifera from the Eocene/Oligocene boundary of Tanzania. Cushman Foundation for Foraminiferal Research, Special Publication. 45: 1-85. gs V O

Spezzaferri, S., Olsson, R. K., Hemleben, C., Wade, B. S. & Coxall, H. K. (2018d). Taxonomy, biostratigraphy, and phylogeny of Oligocene and Lower Miocene Globoturborotalita. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 46(Chap 8): 231-268. gs V O

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina ouachitaensis gnaucki Blow & Banner 1962

Globigerina ouachitaensis gnaucki

References:

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