An analysis of phytolith assemblages for the quantitative reconstruction of late quaternary environments of the lower taieri plain, otago, South Island, New Zealand II. Paleoenvironmental reconstruction

Fossil phytolith assemblages from a 154.5 m longdrill core from the Lower Taieri Plain, Otago, New Zealand are presented. Transfer functions, based on modern phytolith assemblages from sites within the same region, were applied to the fossil phytolith data set, and validated using Modern Analogue Technique (MAT) assemblage matching. Analogues for much of the Holocene and some of the Last Interglacial (provisionally Oxygen Isotope Stage 5c) were obtained. Late Glacial/Holocene precipitation and pH estimates are consistent with other paleoclimate records from the Otago region. The phytolith-based precipitation and pH estimates may act as a combined proxy for soil weathering. The precipitation estimates may also act as a useful index of Effective Precipitation (EP). Temperature estimates derived have limited use for paleoclimate interpretation. Estimates produced for the mid-Holocene indicate a wetter environment than the present (50-100 mm greater EP) with increased soil weathering (high precipitation/low pH). Soil conductivity estimates were below estuarine levels during a diatom inferred marine transgression. This lack of phytolith response to conductivity changes is put down to a probable delayed development of suitable habitats for saltmarsh plant species during the rapid transgression. The Last Interglacial estimates indicate conditions somewhat drier (200 mm less EP) than the Holocene. Consistently low log conductivity (below 0.7 μS cm) estimates from the Last Interglacial contrast with the estuarine environments of the Holocene, indicating freshwater conditions in the Plain during at least part of the Last Interglaciation.