The geochemical characterisation and chronological significance of quaternary tephra deposits in Greater Australia

This thesis repol1s the first detailed tephra study for the Australian mainland. Recent methodological developments were applied for the optimisation and analysis of individual shards from long palaeoenvironmental' sequences in the Western Plains (VictOlia) and the Atherton Tableland (Queensland). In addition, visible tephra layers in Papua New Guinea were carefully characterised using grain-discrete methods to generate the first accurate major oxide compositional database for the region. Many volcanic craters in the Western Plains were successfully characterised'and found to be compositionally distinct. This infonnation was used to source tephra layers found in local mid-late Quaternary sequences. The results challenge previous assumptions regarding the nature of volcanism in the Newer Volcanic Province. In contrast, a general absence of locally-derived glass shards in the Atherton Tableland region raised concerns that weathering was a dominant control. An experiment was initiated to test the effects of wann acidic conditions on the geochemical stability of tephra. The results showed that detelioration does not compromise the compositional integrity of shards provided the leached surficial layer is removed by polishing prior to analysis. The identification and characterisation of a distal tephra on the Athel10n Tableland represents a significant development in this study. Comparison with limited western Pacific tephra compositional records and data generated in this work, strongly suggests a Papua New Guinea source. Late Q1!aternary volcanism is generally locally-produced in Australia. This distal find is clUcial; it demonstrates that the potential for tephra research is not restricted to areas proximal to volcanic sources. Detailed geochemical analyses for visible tephra layers in Papua New Guinea were used to test links between local late Holocene sequences, previously based on bulk volcanic constituents alone. This new approach highlights misplaced correlations and generated moi'e robust links. The value of grain-discrete tephra analytical methods in Papua New Guinea has previously been overlooked. This study de,m.-onsh:~tes that grain-d.iscrete geochemical analysis is of paramount importance and should be adopted in future.EThOS - Electronic Theses Online ServiceGBUnited Kingdo