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(Galloway and Wissler, 1927)

Trochospiral, non-spinose, with 4-5 chambers in last whorl, rather open umbilicus and usually calcite crust. Spiral side flat, apertural side lower than in Globorotalia truncatulinoides (more conical in latter). Aperture extraumbilical, no lip. Periphery rounded and only slightly keeled on last and penultimate chamber in adult specimens. Resembles Globorotalia inflata, but with more angular outline.

Ref.: Parker (1962), Parker and Berger (1971), Lidz (1972), Rögl (1974), Zougary-Jaadi and Pujol (1987).

Distribution: Tropical to subtropical, normally not present south of 30°S (Van Leeuwen, 1989). Although only a minor constituent of typical deep-living planktic foraminifers, it has an interesting habitat. It shows frequency maxima at the eastern edge of the Angola-Benguela Front (17°10 S, 8°54 E), and at the Equator, both areas of high productivity (Berger and Herguera, 1992). As previously reported by Jones (1967), its greatest abundance is observed in the equatorial oxygen minimum zone between 100 and 300 m (abundance of species 6 , Globorotalia crassaformis 4 ). Van Leeuwen (1989) noted a peak in sediments off the Zaire River, where there is a pronounced oxygen minimum layer at depths of 300-400 m (Van Bennekom et al., 1978). Optimum conditions for Globorotalia crassaformis include a shallow thermocline, high productivity in surface waters, and a distinct subsurface oxygen minimum where sinking organic matter is oxidized. Thus, enhanced numbers of Globorotalia crassaformis in the sediments may indicate this type of oceanographic setting. In the western South Atlantic this species is not found along the Brazilian coast between 8°N and 32°S (Bénier, 1985), and has never been recorded farther south.

Remark: = Globorotalia punctulata

Globorotalia crassaformis