Review of Kapitean stratotype and boundary with Opoitian Stage (upper Neogene, New Zealand)

Publisher Website
Google Scholar
Abstract
Criteria for the Kapitean-Opoitian boundary require revision because the systematics of planktic foraminifera cited originally have been refined and usage no longer adheres to the definition. Globorotalia inflata, originally cited, is currently restricted to forms resembling the modem morphotype which first became common in upper Opoitian. From a review of the Kapitean stratotype, 2 options for recognition of the upper boundary are evaluated and submitted for assessment by local biostratigraphers. 1. First appearance of Globorotalia puncticulata sphericomiozea. This datum is easily discriminated as it marks the onset of rapid change in shell morphology. It is located close to the highest occurrence of Kapitean molluscs, possibly preserves original usage at the stratotype, and corresponds with the position of the Miocene-Pliocene boundary. 2. Lowest joint occurrence of G. puncticulata puncticulata and G. crassaformis (typical form). Both taxa are difficult to separate from their forerunners, reducing stratigraphic precision. They usually appear in close proximity, but their order is variable. The datum does not coincide with molluscan or floral events. However, many modem foraminiferal determinations of the boundary are in the vicinity of this datum and it would conserve usage.