Catalog - Globotruncana lugeoni angulata

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.

Globotruncana lugeoni angulata

Citation: Globotruncana lugeoni var. angulata Tilev 1951

Type locality: Cuttings from depth of 1304 meters in the Ramandag well no. 6, Ramandag, southeatstern Turkey.

Type repository: Lausanne - Musee Geologique de l'Universite de Lausanne, Switzerland

Translated from French.
Test: slightly convex or flat dorsally, very strongly convex ventrally. Chambers very rounded in the lower part of the test. On the dorsal side, the chambers of the internal whorls are semicircular in shape, but become roughly trapezoidal in the last whorl. The test displays a circular outline, the chamber sutures of the last whorl meeting the periphery at a well-marked angle.
Profile: Slightly concave or flat dorsally, strongly convex ventrally.
Keel: On the dorsal side the test is bordered by a beaded keel at the beginning of the external whorl, becoming plain in the younger chambers. The beaded ornamentation is stronger along the spiral sutures. The first spiral suture is not clearly perceptible, the central part of the dorsal side being filled with pustules bigger in size than the beads. The keel appears to be broader on the dorsal side than in profile view, its axial projection being a continuous slightly undulated line.
Chambers: 1) The shape of the chambers of the internal whorls quite differs from the shape of the chambers of the external whorl. In the penultimate whorl, the shape is rather semicircular becoming trapezoidal, with a large convex base and an opposite concave base. This particular shape is not always conspicuous in each peripheral chamber; nevertheless, some display it quite well. The outline of the dorsal side is circular not lobate.
2) Shape of the chambers of the last whorl on the ventral side: roughly elliptical in shape, being separated by radial sutures or convex in a frontward direction, shaping grooves between the convex chambers. The inflated surface of these chambers is covered with small pustules lined up along the sutures or around the edge of the umbilicus. The last chamber and the one before are often devoid of this ornamentation. 3) Shape of the chambers in profile view: In profile view, the shape of the chambers is totally similar to that of the Globotruncana lugeoni type; their lower part having the shape of an acorn, their dorsal part being flat and bordered by a keel. The axial projection of the keel is a continuous, slightly undulated line.
Umbilicus: Broad, hexagonal in shape, the convex sides being directed toward the center. The edge of the umbilicus is produced by a periumbilical thickening of the test. This umbilical edge is bounded by pustules on one side and by this epigenetic filling on the other side. The umbilicus is deep, his depth being equal to the height of the shell. Its diameter is more or less half the size of the test diameter.
Axial section: The axial section displays the exact shape of the profile of the test (dorsal side flat, ventral side more convex than a half-circle), the thickness of the test - which is rather reduced - and its internal structure. The chambers become more and more elongate along an axial, inside-outside direction. The chambers of the internal whorls are single-keeled.

Number of whorls: three (the initial whorl being less noticeable). Number of chambers in the last whorls: six to seven.

Variabilité: Cette forme étant très rare dans le matériel que nous avans étudié, nous ne pouvons juger de l'étendue de ses variations.

Répartition stratigraphique: Nous avons rencontré cette variété avec les Gl stuarti, dans la série maestrichtienne, ayant l'apparition en assez grande abondance des Gl. lugeoni type.

Rapports et diffèrences: Cette variété intermédiaire de Globotruncana lugeoni var. angulata ressemble:
1) à Globotruncana stuarti de Lapp.
2) à Globotruncana lugeoni type.
1) Elle diffère de Gl. stuarti par la forme du profil de son test et la forme de gland des loges périphériques, munies de petites perles alignées le long de la ligne de suture, du côté ventral,
2 - Globotruncana lugeoni var. angulata se rapproche beaucoup de Gl. lugeonl type, par la forme de son test (courbure). Elle en diffère par la forme de ses loges (ligne de suture) à la face dorsale. Chez Gl. lugeoni var. angulata, la face dorsale des loges du dernier tour présente un angle d'environ 90 degré avec le contour périphérique du côté dorsal du test. Le contour est continu, non lobé, chez Gl. lugeoni var. angulata, légèrement lobé chez Gl. lugeoni type. Les loges ont tendance à s'allonger dans le dernier tour et s'accroissent rapidement chez Gl. lugeoni type, tandis que dans la var. angulata elles restent plus ou moins parailles à elles-mêmes. En plus, les Gl. lugeoni type possèdent des pustules au milieu des loges, à la face dorsale (1 pustule par loge). Les perles sont généralement plus abondantes à la partie inférieure du test, couvrant parfois même toute la surface, chez Gl. lugeoni type. (voir Pl. I, fig, 5)

References:

Tilev, N. (1951). Tilev, N. (1951). Etude des Rosalines maestrichtiennes (genre Globotruncana) du Sud-Est de la Turquie (Sondage de Ramandaǧ). Maden Tetkik ve Arcana Enstitusu Yayinharindam (Mining Research and Exploration, Institute of Turkey Publ.). Ser. B. Ser. B 16: 1-101. Maden Tetkik ve Arcana Enstitusu Yayinharindam (Mining Research and Exploration, Institute of Turkey Publ.).. 16: 1-101. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globotruncana lugeoni var. angulata Tilev 1951

Globotruncana lugeoni angulata

References:

Add Comment

Comments