Variation in Bolivinita quadrilatera (Foraminiferida, upper Neogene, New Zealand)

Abstract

Bolivinita quadrilatera is a long-ranging species of relatively stable morphology that intermittently inhabited the New Zealand region and developed locally abundant populations in the upper Miocene (Tongaporutuan Stage), lower Pliocene (Opoitian and Waipipian Stages), and about the Pliocene-Pleistocene boundary (Mangapanian and Nukumaruan Stages). Many of the occurrences are from deep-water (outer “shelf” to bathyal) biotopes, and bathymetry may have been a major control over its stratigraphic distribution. Populations previously distinguished as B. granttaylori are considered to be conspecific with B. quadrilatera. Although spiral profiles in B. quadrilatera are mainly quasi-rectangular, a few are rhomboidal as in B. cf. pohana. There is some evidence in support of a morphocline between these taxa, but population distributions in Tongaporutuan strata suggest that they were distinct, although occupying comparable biotopes. The localised distribution of B. quadrilatera, even in favourable, deep-water biotopes is a restriction on its use as a criterion for the base of Tongaporutuan Stage.

Keywords:

• Foraminiferida
• New Zealand
• Miocene
• Pliocene
• Recent
• Bolivinita quadrilatera
• biofacies
• shell morphology
• biometry
• biostratigraphy