Year

2017

Degree Name

Doctor of Philosophy

Department

School of Earth and Environmental Sciences

Abstract

The Quaternary evolution of rivers in southeastern (SE) Australia has been the focus of numerous studies for over half a century. Fluvial records, within the depositional basin of the Riverine Plain west of the Great Dividing Range, are often represented by palaeochannels much larger than the present river channels. Morphologic differences, such as larger bankfull channel widths, larger meander wavelengths and coarser bed-load sediments provide evidence for regimes of higher discharge and stream competence, stemming from significant changes in runoff volumes and sediment supply. Previous dating of some of the Late Pleistocene palaeochannels suggested an association with the Last Glacial Maximum (LGM) but the presence or absence of such palaeochannels varies between catchments. In some catchments it has been suggested that continuous enhanced fluvial activity occurred throughout the LGM, whilst in other basins such fluvial activity is thought to have ceased at the peak of the LGM.

However, the predominant opinion in the literature is that conditions during the LGM in SE Australia were cold and arid which seems to be contradictory to findings of some of the fluvial settings. Recent developments in dating techniques, such as single-grain optically stimulated luminescence (OSL) allow for the examination and validation of previous established chronologies from fluvial archives. The palaeohydrological conditions in three catchments of SE Australia are the focus of this study. Palaeochannel remnants of the Murrumbidgee, Goulburn and Murray rivers that were previously linked to the LGM, were investigated to constrain the timing of activity and the predicted discharge associated with the systems.

Ten sites along palaeochannel systems of the Murrumbidgee River, three sites along the Goulburn River and two sites along the Murray River were investigated. A total of ~240 m of sedimentary core, 39 single-grain OSL ages and for comparison 11 thermoluminescence (TL) ages were obtained. The OSL characteristics of the sediment were investigated and partial bleaching in the modern and Late Pleistocene samples was not identified ...

This thesis is unavailable until Saturday, December 07, 2019

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