Recent Distribution, Origin, and Coiling Ratio Changes in Globorotalia pachyderma (Ehrenberg)

Abstract

Globorotalia pachyderma (Ehrenberg) is sinistrally coiled in polar and subpolar seas and dextrally coiled towards lower latitudes. In the New Zealand Upper Cenozoic, G. pachyderma possibly evolved from Globorotalia continuosa Blow, and there are ten alternating sinistral and dextral populations of G. pachyderma which have been interpreted as indicative of alternating cold and warmer marine conditions. Comparison is made with Upper Cenozoic G. pachyderma coiling ratios of New Zealand, Italy and California. Recent distribution, origin, and coiling ratio changes in Globorotalia pachyderma (Ehrenberg) D. GRAHAM JENKINS New Zealand Geological Survey Lower Hutt, New Zealand