A widespread ca. 1.1 Ma TVZ silicic tephra preserved near Wellington, New Zealand; implications for regional reconstruction of mid-Pleistocene vegetation

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doi: 10.1016/j.quaint.2007.04.006
Author(s): Mildenhall, Dallas C.; Alloway, Brent V.
Author Affiliation(s): Primary:
Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand
U. S. Geological Survey, Earth Surface Processes Team, United States
California State University at Fullerton, United States
University of Waikato, New Zealand
Volume Title: Global tephra studies; John Westgate and Andrei Sarna-Wojcicki commemorative volume
Volume Author(s): Froese, Duane G., editor; Slate, Janet L.; Knott, Jeffrey R.; Lowe, David J.
Source: Global tephra studies; John Westgate and Andrei Sarna-Wojcicki commemorative volume, edited by Duane G. Froese, Janet L. Slate, Jeffrey R. Knott and David J. Lowe. Quaternary International, Vol.178, p.167-182. Publisher: Elsevier, Oxford, United Kingdom. ISSN: 1040-6182
Note: In English. 68 refs.; illus., incl. strat. col., 3 tables, sketch maps
Summary: A sequence of terrestrial pollen-bearing sediments exposed in Transmission Gully (TG), near Wellington, New Zealand contains a prominent ca. 20-cm-thick silicic tephra bed dated at 1.09±0.12 Ma based on ITPFT dating of glass shards. Such occurrences are rare in the Wellington region. The associated palynology, overlying TG tephra, represents vegetation totally different from any modern assemblage with both warm climate taxa, e.g. Lygodium articulatum, Toronia toru, and cool climate taxa, e.g. Acaena, Apiaceae, Epilobium, Gentiana, Lycopodium australianum, Taraxacum, and Wahlenbergia, occurring together. A pollen assemblage 0.4 m above the base of TG tephra comes from a southern beech forest existing under warm temperate conditions, with both Fuscospora and Nothofagus menziesii beeches, and an abundance of ferns and lycopods represented. Beeches rapidly disappeared from around the site of deposition until at 0.6 m above the base of TG tephra beech pollen were rare and the pollen assemblages were dominated by grass. Ferns and lycopods were still well represented but the dramatic increase in grass pollen suggests that the environment outside the immediate depositional site had become much drier. A ca. 0.64-m-thick gravel layer was then deposited which impeded drainage. Associated pollen assemblages were then dominated by sedges and grasses in approximately equal percentages, although conditions may have still been relatively dry. Overall, the pollen assemblages are indicative of a sedge swamp surrounded by grassland with distant beech forest. Since the glass ITPFT-age range (±1 SD) for TG tephra extends over Oxygen Isotope Stages (OIS) 37 to 26, the fossiliferous sequence overlying the tephra should be any of the five periods of relative warmth, in spite of the lack of tree pollen and dominance in the profile of herbaceous taxa. However, geochemical comparison of TG tephra with those preserved in ODP site 1124, and two equivalent-age sequences in Auckland region (Patiki Core Site, Okariha) suggest a correlation with OIS 35. On this basis, the presence of Beaupreaidites diversiformis 0.4m above the base of TG tephra provides a date for the final extinction of the modern New Caledonian genus Beauprea in New Zealand. Pollen from Toronia toru occurs throughout the sequence, far further south than in any other Pleistocene sequence so far analysed.
Year of Publication: 2008
Research Program: ODP Ocean Drilling Program
Key Words: 03 Geochronology; 24 Surficial Geology, Quaternary Geology; Acidic composition; Assemblages; Australasia; Cenozoic; Correlation; Depositional environment; East Pacific; Electron probe data; Fission-track dating; Geochemistry; Geochronology; Glasses; Igneous rocks; Leg 181; Microfossils; Middle Pleistocene; Miospores; New Zealand; North Island; ODP Site 1124; Ocean Drilling Program; Pacific Ocean; Paleoclimatology; Paleoecology; Paleoenvironment; Palynomorphs; Pleistocene; Pollen; Pyroclastics; Quaternary; Relative age; Rhyolitic composition; South Pacific; Southeast Pacific; Tephrochronology; Vegetation; Volcanic glass; Volcanic rocks; Wellington New Zealand
Coordinates: S392954 S392954 W1763154 W1763154
S413000 S410000 E1750000 E1743000
Record ID: 2009065587
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands