Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf
Author
Bergh, Eugene W.
0000-0002-0765-4141
Marine Research Institute and Department of Geological Sciences, University of Cape Town, Private Bag X 3, Rondebosch, 7701, South Africa. & Department of Environmental and Geographical Sciences, University of Cape Town, Private Bag X 3, Rondebosch, 7701, South Africa; & Invertebrate palaeontology and Geology, Iziko South African Museum, P. O. Box 61, Cape Town 8000, South Africa. john. compton @ uct. ac. za; https: // orcid. org / 0000 - 0002 - 0765 - 4141
john.compton@uct.ac.za
Author
Compton, John S.
Marine Research Institute and Department of Geological Sciences, University of Cape Town, Private Bag X 3, Rondebosch, 7701, South Africa.
text
Zootaxa
2022
2022-01-12
5091
1
1
55
journal article
2636
10.11646/zootaxa.5091.1.1
51b42715-ddb1-4b4a-aad4-8be0f600a287
1175-5326
5840434
ABC8AF70-F691-4D07-8F20-70934642C8BC
Globigerinoides subquadratus
Brönnimann, 1954
Pl. 7, figs. 11–12
Globigerinoides subquadratus
Brönnimann, 1954
, p. 680
, pl. 1, fig. 8;
Kennett & Srinivasan, 1983
, p. 74
, pl. 10, fig. 4; pl. 16, figs. 1–3.
Description
: The wall surface is macroperforate and cancellate-spinose. The test is trochospiral, sub-globular to sub-quadrate in shape and semi-circular in cross section. The chambers are sub-rounded to sub-quadrate in shape, with two basal chambers on the umbilical side, separated by a straight deep incised suture, which is overarched by a large chamber. The final chamber comprises approximately half the size of the test. The primary aperture is large and forms an arch symmetrically above the two basal chambers in apertural view. Two supplementary apertures form on the spiral side of the test along sutures of earlier chambers.
Remarks:
The relative abundances of
Gs. subquadratus
are major (<25%) in samples along the Mio-Pliocene contact of all three cores, increasing in abundance in the deeper cores. The tests of
Gs. subquadratus
are relatively small, measuring
0.3 mm
in diameter.
This species is very similar to
Globigerinoides ruber
,but are stratigraphically separate and can be morphologically differentiated.
Gs. subquadratus
is identified in the Miocene, whereas
Gs. ruber
is extant and occurs in younger strata. Morphologically, the shape and outline of the test and chambers of
Gs. subquadratus
is more quadrate in shape compared to
Gs. ruber
(
Bolli
et al.,
1985
)
.
Environmental preferences:
Gs. subquadratus
is associated with
Neogene
tropical environments (
Brönnimann
et al.,
1971
;
Wade
et al.,
2011
).
Global stratigraphic range
: This species occurs in Miocene strata from the Aquitanian to Tortonion (
Kennett & Srinivasan, 1983
;
Wade
et al.,
2011
).
Regional occurrence:
Gs. subquadratus
has been identified in middle Miocene strata from the
Congo
Basin (
Kender
et al.,
2008
) and the northern Namibian outer continental shelf, south of the Kunene River mouth (this study).