School of Geography - Theses
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ItemSpeleothem-based explorations of millennial-scale climate change in southern Australasia(2018)Understanding the way Earth responds to rapid climate change is critical for understanding future climate scenarios. The best natural examples of rapid climate change are found in millennial-scale climate events recorded in Greenland ice cores over the Last Glacial Period (120-12 ka). These occur concurrently with similarly-paced, gradual warming events recorded in Antarctic ice cores. Understandings of the transition between Greenland-like and Antarctic-like millennial-scale climate events are limited by a lack of appropriate records from the southern mid-latitudes. However, calcite cave formations (speleothems) have the potential to record high-resolution millennial-scale climate change in this region. This study looks at three southern mid-latitude cave sites, develops or improves palaeoclimate reconstructions from each, compares these to external records of millennial-scale climate change, and assesses the suitability of each site for future millennial-scale palaeoclimate reconstructions. Palaeoclimate reconstructions were produced based on U-Th dating, stable isotope analysis and trace element analysis techniques. The first ever high-resolution palaeoclimate record from Naracoorte, Australia from the Last Glacial Period was produced, which suggested that millennial-scale climate change here was influenced by changes in the activity of the southern westerlies. The first ever palaeoclimate record from Wombeyan, Australia was produced, which suggested that millennial-scale climate change here was confounded by both tropical and mid-latitude climate effects. An existing palaeoclimate record from Nettlebed was improved upon and reinterpreted, which supported previous findings that millennial-scale climate in Nettlebed is influenced by the intensity of the southern westerlies. Naracoorte and Nettlebed demonstrated good potential for future millennial-scale palaeoclimate reconstructions, although Naracoorte is limited by a lack of speleothem samples from the Last Glacial Period. Wombeyan demonstrated poor potential for future millennial-scale palaeoclimate reconstructions due to its confounded climate signature, and high U-Th age uncertainties due to low speleothem uranium concentrations. These findings have implications for the future study of millennial-scale climate change, by presenting brand new millennial-scale palaeoclimate reconstructions and demonstrating how future millennial-scale palaeoclimate reconstructions can be developed from a critically under-sampled region.