Catalog - Globigerina atlantica

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Globigerina atlantica

Citation: Globigerina atlantica Berggren 1972

Type specimens: Holotype: The holotype specimen (plate 2, fig. 8) is from sample 116A-8-CC (late Pliocene). The neotype and paraneotypes are from the same sample and are deposited in the collections of the European Micropaleontological Reference Centre, Krakow, Poland, and housed in Cabinet 7, drawer 23.

Type sample (& lithostrat): DSDP 116A-8-CC,

Type age (chronostrat): late Pliocene

Type repository: not stated - possibly USNM;

Diagnosis: A 4-5 chambered globigerinid characterized by a relatively coarse granular surface, large apertural viarability and, during the Pilocene, by pronounced sinistral coiling.
Description: The adult test is average sized to large for the genus, coiled in a tight low-trochospire with 4-5 chambers gradually increasing in size in the final whorl. The final chamber, usually the fifth, is often diminutive and caplike, extending in some instances down over the umbilicus. The test outline is broadly oval and the peripheral margin strongly lobulate. The intercameral sutures on the umbilical side are radial to slightly curved and distinctly incised. The primary aperture is a relatively low, narrow opening above the umbilicus but in some specimens it extends laterally towards, but not up to, the peripheral margin. An apertural lip is generally absent, the distal margin of the apertural region being developed as a thickened rim with spines being developed up to the edge; in rare instances a flanging lip is developed, particularly between the last two chambers. The calcareous wall is thick, and the test surface is densely covered with bluntly pointed spines giving the test a distinctly "granular" appearance. Within the umbilical region the spines are longer and sharper and somewhat less dense in their spacing. The species is consistently sinistrally coiled in the Pliocene, whereas pre-Pliocene forms exhibit a preference for dextral coiling.

from its abundant occurrence in the North Atlantic sediments cored on Leg 12.

Remarks: This species is the dominant globigerinid and, indeed, the dominant planktonic foraminifer in most Pliocene samples in the North Atlantic encountered on Leg 12. In some instances it constitutes over 90% of the total planktonic foraminiferal fauna. It exhibits a preference for dextral coiling in the late Miocene but exhibits a pronounced sinistral coiling pattern in the Pliocene (over 95%) up to its extinction at the Pliocene/ Pleistocene boundary.

This species is markedly similar to Globoquadrina dutertrei; it differs, however, in its consistently tighter coiling (and consequently narrower, smaller umbilicus), the greater variability of its aperture and in the "granular" test texture. This "granular" test texture is reminiscent of similar morphology developed in some forms of the genus Acarinina in the Paleogene. Indeed, the general test shape, outline and morphology of Globigerina atlantica is strongly similar to that developed in Acarinina mckannai and A. pentacamerata (=A. gravelli) during the late Paleocene and early Eocene. Globigerina atlantica also exhibits a general similarity to Globigerina pachyderma but can be distinguished by consistent size differences, in addition to discrete morphologic differences. G. pachyderma makes its initial appearance in all North Atlantic cores coincident with the first evidence of glaciation (ice-rafted detritus) and the two species are the dominant forms in upper Pliocene samples of the North Atlantic.

The present species may be related to the "Globorotalia" humerosa-Globoquadrina dutertrei group but at the present time it is not possible to discern definite kinship or Phylogenetic trends in this highly complex and variable group. It would appear that this species has been recorded in the late Neogene of the Mediterranean region by Italian workers, but a more thorough comparison of actual specimens from this region must be made before this can be confirmed. Globigerina atlantica has been recorded from sites 111, 112, 113, 114, 116 and 118 of Leg 12.

Stratigraphic Range: Globigerina atlantica has been observed from the late Miocene to late Pliocene (Zone N16-N21) in the North Atlantic. Sporadic and questionable occurrences in middle Miocene (Serravallian) samples-Zones N14-N15-have been observed.

Kaminski & Berggren 2021 designated and illustrated a Neotype specimen from the original type residue, since the holotype is missing.

References:

Berggren, W. A. (1972). Cenozoic biostratigraphy and paleobiogeography of the North Atlantic. Initial Reports of the Deep Sea Drilling Project. 12: 965-1001. gs V O

Kaminski, M. A. & Berggren, W. A. (2021). A Neotype for Neogloboquadrina atlantica (Berggren 1972). Micropaleontology. 67(1): 106-107. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerina atlantica Berggren 1972

Globigerina atlantica

References:

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