School of Geography - Theses

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Type: Masters Coursework thesis × Start date: 2010 × End date: 2020 × Subject: Australia ×

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    Speleothem-based explorations of millennial-scale climate change in southern Australasia
    Gordon, Jay ( 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.