Catalog - Globigerina clarkei

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Globigerina clarkei

Citation: Globigerina clarkei Rögl & Bolli 1973

Type age (chronostrat): Deep Sea Drilling Project, Leg 15, Site 147, Core 4, core-catcher (32.00 m). Type stratum: Late Pleistocene; Globorotalia truncatulinoides truncatulinoides Zone, Globigerina bermudezi Subzone; Zone Y after Ericson and Wollin.

Type locality: Cariaco Basin, Caribbean Sea: lat 10°42,48'N; long65°10,48'W.

Type repository: Basel, CH; Natural History Museum

Shape of test very low trochospiral, axially compressed; equatorial periphery subcircular — elongate, slightly lobulate; axial periphery rounded. Ten subglobular axially compressed, tightly arranged chambers, five in the last whorl, final chamber slightly radially elongate. Sutures distinct, fairly incised, radial. Umbilicus small, shallow. Aperture a narrow slit, umbilical - extraumbilical, with aperture flap. Wall very thick, almost smooth, only slightly transparent, with few but large and widely spaced pores, no spines visible.

Dimensions (holotype): maximum diameter 0.135 mm; minimum diameter 0.118 mm; height of test 0.062.mm. Dimensions (paratypes): Maximum diameter 0.103-0.132 mm; average 0.117 mm; minimum diameter 0.086-0.132 mm, average 0.099 mm. Number of chambers (paratypes): 9-13, average 11.31.

The shape of test is intermediate between Globigerina quinqueloba and Turborotalita humilis, somewhat elongate, only slightly lobulate and axially compressed. Nine to thirteen chambers in two to two and a half whorls. Final chamber radially elongate. Aperture narrow, usually with an apertural flap, extending towards the umbilicus. In specimens with very thick walls the apertural slit may become almost completely closed (Plate 4, Figure 15). The wall is very thick; in more delicate specimens it may be covered by fine, spine-like rugosities, similar to the bases of spines in Globigerina quinqueloba.

Remarks: Until the origin of the new species is established it is placed in Globigerina with some reservation.

Differential diagnosis: The new species appears to be closest to Globigerina quinqueloba from which it differs in the smaller size, thickness of chamber wall and the more umbilical-extraumbilical position of the aperture. With largest diameter varying between 0.11 to 0.25 mm with an average of 0.19 mm, and 11 to 18 chambers, average 13.3 chambers, Globigerina quinqueloba of Site 147, though small in size, is distinctly larger than the new species. According to Parker (1962, p. 225) G. quinqueloba reaches up to 0.27 mm in diameter. The test is also more compressed, the chambers less inflated and closer arranged in the new species, with shallower and less distinct intercameral sutures.
Turborotalita humilis which possesses a similarity compressed test of about equal size in Site 147 as Globigerina clarkei n.sp., always has six to seven chambers in the last whorl against five in the new species. Turborotalita humilis is further more circular in equatorial outline and the much narrower chambers are more closely attached. The last chamber is not bulla-like in Globigerina clarkei n. sp. as it is in T. humilis.
Occurrence: With some interruptions throughout Site 147, more frequent in the lower part of the section of Site 147. In Site 147, from Late Pleistocene to Holocene, Globorotalia truncatulinoides truncatulinoides Zone; after Brönnimann and Resig, 1971, from Middle Pliocene to Middle Pleistocene.
The species is named for Captain J.A. Clarke, master of the Glomar Challenger.

References:

Rögl, F. & Bolli, H. M. (1973). Holocene to Pleistocene planktonik foraminifera of LEG 15, site 147 (Cariaco Basin (Trench), Caribbean Sea) and their climatic interpretation. Initial Reports of the Deep Sea Drilling Project. 15: 553-579. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina clarkei Rögl & Bolli 1973

Globigerina clarkei

References:

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