Strong CP. 2019. Uppermost Teurian to lowermost Bortonian foraminiferal biostratigraphy of the Mead Stream section, Clarence River valley, Kaikoura district, New Zealand. Lower Hutt (NZ): GNS Science. 32 p. (GNS Science report; 2019/250. doi:10.21420/E2T1-HC11.
This report reviews and revises foraminiferal samples collected over some 3 decades from c. 245 m of the medial Amuri Limestone at Mead Stream, including all the Lower Marl and Upper Limestone, together with adjacent strata of the Lower Limestone and Upper Marl. These strata range from in age from Late Paleocene to Middle Eocene, however, most of the samples are Early Eocene in age. One-hundred and two samples were previously studied, 35 are new records, and an additional 6 new samples were determined to be non-fossiliferous. A consistent taxonomy was applied to all faunas. All data presented here pre-date the 2017 Kaikoura Earthquake, which may have adversely affected exposures of the section described here. However, this remains to be determined. With few exceptions, foraminiferal faunas indicate that the entire succession was deposited at lower middle bathyal to lower bathyal depths, beneath an oceanic to perhaps sub-oceanic water mass. There was apparently significant variation, over time, in mixed layer and thermocline relationships, and oceanicity appears to be more variable in the lower Mangaorapan and Waipawan. Integration of foraminiferal, magnetostratigraphic and carbon-isotope excursion results potentially provide more accurate absolute ages for the Bortonian and Mangaorapan stage boundaries, as well as other events. The well-constrained Waipawan-Mangaorapan stage boundary may be a strong candidate for the currently undefined Mangaorapan boundary stratotype. (auth)