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A high resolution record of Late Quaternary vegetation and climate change, south Westland, New Zealand

Marcus J. Vandergoes
Department of Geography, University of Otago, Dunedin, New Zealand

 
Abstract

Three pollen records from south Westland, New Zealand, extending from the Holocene boundary to beyond the Last Glacial Maximum provide new insights into the vegetation and glacial history of this region. Dacrydium cupressinum forest characterises the base of the longest record (>45 ka BP) and may record vegetation of the last interglacial. A low shrubland of Phyllocladus, Myrsine, and Halocarpus characterise the regional vegetation after this time. Grassland and shrubland are dominant between c. 20 - 14.5 ka BP, which represents the Last Glacial Maximum. A decrease in grassland representation and an increase in Dacrydium cupressinum and shrubland in tow of the sequences during this time may record a warm period. High-resolution analysis of the late glacial period reveals evidence of changes in local vegetation composition around the time of the European "Younger Dryas" Chron, but is not conclusive of regional climate cooling between c. 12 - 10 ka BP. In contrast, vegetation changes at this time are more consistent with increasing precipitation and temperature. The Holocene is represented by warm temperate podocarp forest, which persists until the present day. Data from these records suggest that the mechanisms responsible for the strong cooling associated with the European Younger Dryas had little or no influence on southern New Zealand climate and support theoretical models of interhemispheric climate change that propose an anti-phase climate association between the Northern and Southern Hemisphere. Uncertainties in the AMS chronology of the record have resulted in two possible interpretations for the pollen sequences beyond c. 20 ka BP: first, the sequences represent a continuous record of vegetation and climate change since the last interglacial, and second, the sequences represent a continuous record of vegetation and climate change covering the last c. 45 ka years. Pollen fraction dating provides a more reliable chronology for the sequences and suggests that younger carbon contamination is the main cause of dating inconsistencies in the chronology. Vegetation changes inferred from these pollen records are considered to be driven primarily by climate change including variations in temperature and precipitation, and to a lesser extent forest succession, disturbance, and soil development.

 
Reference

Vandergoes, M.J. 2000. A high resolution record of Late Quaternary vegetation and climate change, south Westland, New Zealand. Unpublished PhD thesis, in Geography, at the Unversity of Otago, Dunedin, New Zealand.  149 pp.

© 2009 Department of Geography, University of Otago, Dunedin, New Zealand