The Last Glacial–Interglacial Transition (LGIT) in south Westland, New Zealand: paleoecological insight into mid-latitude Southern Hemisphere climate change

Abstract

High resolution pollen stratigraphy from three peat cores located within 20 km of Lateglacial moraines in south Westland, New Zealand provide detailed records of climate change during the Last Glacial–Interglacial Transition (LGIT). The pollen record shows the replacement of grassland by shrubland prior to ca 15,300 14C yr BP (18,300 cal. yr BP) followed by the progressive development of broadleaf shrubland and scattered forest prior to ca 12,000 14C yr BP (14,400 cal. yr BP). Local vegetation changes around the time of the Younger Dryas chronozone (11–10 ka 14C BP) are evident, but are not necessarily a result of regional climate cooling. Vegetation changes between ca 12,000 and 10,000 14C yr BP (14,400 and 11,400 cal. yr BP) indicate a period of increased precipitation. Tall podocarp forest, similar to that of the contemporary forest, was well established by ca 10,000 14C yr BP (11,400 cal. yr BP). A period of increased westerly circulation over southern New Zealand is considered to be the most likely mechanism for causing the increased precipitation between ca 12,000 and 10,000 14C yr BP (14,300 and 11,400 cal. yr BP). Increased precipitation would also provide a mechanism for initiating LGIT ice advance in the area. Data from these records show some support for global climate change models that propose inter-hemispheric linkage, but may be more supportive of a climate change model that incorporates an increased westerly circulation over southern New Zealand during the LGIT.