Revision of hutchinsonian, awamoan and altonian stages (lower miocene, new zealand) — 2

Abstract

Foraminifera suitable as criteria for subdivision of the stratigraphie interval between the Otaian and Clifdenian Stages are evaluated. Globorotalia scitula praescitula Blow, G. zealandica zealandica Hornibrook, and Globigerinoides trilobus trilobus (Reuss) are distinctive and widespread but all appear close to· the present Otaian/Hutchinson- ian boundary. Globorotalia miozea miozea Finlay appears higher in the interval but seldom occurs in strata deposited in shallow marine environments. The Altonian Stage is emended to embrace the stratigraphic interval between the top of the Otaian Stage and the base of the Clifdenian Stage. The Hutchinsonian and Awamoan Stages are synonymised with the emended Altonian Stage. Inception of uniserial chamber arrangement in a specified subset of individuals in the Haeuslerella pukeuriensis Parr lineage is the primary criterion for the base of Altonian; the appearances of Globorotalia scitula praescitula and Globigerinoides trilobus trilobus indicate superior proximity to the base. The appearances of Globorotalia zealandica zealandica, Globoro-talia miozea miozea and Rectobolivina maoria Finlay are cited as successive, intra-stage criteria. The appearance of Praeorbulina Olsson defines the Altonian/Clifdenian boundary. The Pareora Series is emended to include the Otaian and Altonian Stages. © 1972 Taylor & Francis Group, LLC.