Globorotalia truncatulinoides Datum Plane: Evidence for a Gauss (Pliocene) Age in Subantarctic Cores

Abstract

IN the past, the first appearance of the planktonic foraminifer Globorotalia truncatulinoides (d'Orbigny) was one of the most reliable Neogene foraminiferal datum planes. It was widely accepted as marking the onset of the Pleistocene at about 1.8 m.y. BP during the Matuyama Magnetic Epoch1, but this datum must now be restricted in the southern hemisphere to areas north of about 36° S. A concurrent analysis of radiolarians and planktonic foraminifers in 18 deep-sea cores (12 of which were dated palaeomagnetically) from south of Australia and the Tasman Basin (Table 1; ref. 2) demonstrates that, in that area, G. truncatulinoides appeared during the Gauss Epoch. This predates its appearance in lower latitudes by 1–1.5 m.y.