Where is the boundary between New Zealand’s western and eastern provinces? A case study in describing terrane relationships using cladistic methods.

Abstract

ABSTRACTA cladistic analysis of 21 geological characters taken from the literature is used to determine the relationship between the Drumduan Terrane, Takaka Terrane (Western Province), and Brook Street Terrane (Eastern Province) of Nelson, New Zealand. We present the analysis as a case study to illustrate the utility of a cladistic approach to describing terrane relationships. The results of the analysis support the placement of the Drumduan Terrane as the eastern boundary of the Western Province providing the Pepin Group and Echinus Granite are the basement of the overlying Marybank Formation sediments rather than being tectonically juxtaposed. The importance of establishing whether the Drumduan Terrane and its proposed correlatives in Fiordland and Stewart Island are part of the Western or Eastern Province is that natural groupings can be identified and tectonic reconstructions can be free of artifice.