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Methods and materials

Fifty one samples were analyzed for palynology between 91.1 and 181.5 mcd. Samples were processed as described in Crouch et al. (2010) and Prebble et al. (2013) at the GNS Science Palynology Laboratory, Lower Hutt, New Zealand. This laboratory has positive filtered air pressure to minimize contamination during processing. Samples of 5 cm3 were oven dried at 50°C for 24 h and then weighed. A Lycopodium tablet (batch Number 938934) was added to obtain absolute abundance counts (e.g., Mertens et al., 2009). Cold 10% HCl was added to the dried sample to remove carbonates, followed by 24 h in cold 52% HF and a second 10% HCl wash. Samples were placed in an ultrasonic bath for up to 1 min, sieved through 6 µm mesh to remove small particulate material, and then mounted on glass slides in glycerine jelly. All slides and residues are held in the paleontology collections at GNS Science.

All counts were completed on a light microscope at 500× magnification. For most samples two entire slides were examined. For dinoflagellate cysts, taxonomy and nomenclature followed Zonneveld (1997), Rochon et al. (1999), Marret and Zonneveld (2003), Radi et al. (2013), and references therein, with identification to species level where possible. Broken cysts were counted per 0.25 of a specimen. For pollen and spores, identification was mostly to a generic level and followed Pocknall (1981a, 1981b, 1981c), Large and Braggins (1991), and Moar (1993). Some taxa, including the frost-intolerant Ascarina lucida, were grouped into an “undifferentiated angiosperms” category. Division within the podocarps followed Heusser and Van der Geer (1994), with Dacrydium cupressinum, Dacrycarpus dacrydioides, Halocarpus sp., and Phyllocladus spp. differentiated, whereas Prumnopitys spp. and Podocarpus spp. were grouped. Fuscospora fusca pollen, Lophozonia menzeisii, and Trisyngyne brassii were separated. Cyathea spp. and other trilete and monolete spores were counted outside of the dry land sum. Notwithstanding the exceptions outlined above, nomenclature followed Moar et al. (2011).