Integrated micropaleontology of the Waihapa-1 and Toko-1 wells, onshore Taranaki, New Zealand

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Morgans, H.E.G.; Waghorn, D.B. 1999 Integrated micropaleontology of the Waihapa-1 and Toko-1 wells, onshore Taranaki, New Zealand. Lower Hutt: Institute of Geological & Nuclear Sciences. Institute of Geological & Nuclear Sciences science report 99/18 63 p.

Abstract: Calcareous nannofossil distributions are combined with existing planktonic and benthic foraminiferal data to produce an integrated biostratigraphy for the marine interval of the Toko-1 and Waihapa-1 wells. This data is summarised and presented in two time-depth plots which show correlation of the lithostratigraphy with the New Zealand Stages and the International Time Scale, paleoenvironments, deposition rates and the interpreted position of unconformities or condensed sections. Integration of microfossil groups improves biostratigraphic resolution by providing more datums (biostratigraphic events such as the top or base of a fossil range) for correlation with the New Zealand Stage and International Chronostratigraphic Schemes. New calcareous nannofossil data are presented which improve resolution for the Oligocene interval. Although Miocene nannofossil assemblages are not particularly diverse several taxa occur which provide correlation with the International time scale of Berggren et al (1995). Foraminiferal, especially planktonic foraminiferal, biostratigraphy is much better understood although nannofossils can improve the interpretation of foraminiferal assemblages by constraining distributions and allowing reworking and downhole caving to be more readily identified. Integrated results show that the top of the Tikorangi Formation is isochronous between the Toko-1 and Waihapa-1 wells and that the mid-Oligocene or Marshall Paraconformity can be correlated with the boundary between the Matapo Greensand and overlying Otaraoa Formation, at the base of the marine section investigated in this report. (auth)