Year
2011
Degree Name
Bachelor of Science (Honours)
ANZSRC / FoR Code
040303 Geochronology, 040310 Sedimentology, 040312 Structural Geology
Department
School of Earth & Environmental Sciences
Recommended Citation
Barrett, Ali C., Deltas, dunes and playas: the evolution of a Lake Frome embayment from the late Quaternary to the present day, Bachelor of Science (Honours), School of Earth & Environmental Sciences, University of Wollongong, 2011.
http://ro.uow.edu.au/thsci/7
Abstract
The response of the Australian landscape to future climate change can be gauged by studying the effects that climatic change has had on environments in the past. The timing, extent and synchronicity of the lacustrine and playa periods which were experienced in the north and south of the Australian continent during the Quaternary are still not well understood. A detailed understanding of the climate drivers and the response of the Australian landscape at this time to climatic variables would not only help us to plan for future climate change it would also help to answer key questions such as the reasons for megafaunal extinction and the extent to which the first humans in Australia modified this environment.
Lake Frome is a playa lake located in the south of the Lake Eyre Basin in South Australia. A study site was identified along the western shoreline of the playa lake which is dissected by ephemeral streams that rise in the Flinders Ranges and characterised by a large number of what appear to be bank attached spits. This study demonstrates that playa shoreline features which appear to be beach ridges are actually relict fluvio deltaic units. A combination of thermoluminescence, accelerator mass spectrometer
14C and amino acid racemisation ages provide bounding timeframes for the investigation of two such fluvio-deltaic features and adjacent lake floor facies and aeolian landforms. The ages are combined with a study into the stratigraphy and microfossil ecologies at the site and reveal a mega high lake stage at around 110-100 ka and two major periods of high volume runoff from the Flinders Ranges between 92-80 ka and 17-11 ka during which lake levels were at a minimum elevation of 4-6m (AHD). Following this a transition to ephemeral conditions was experienced at this site between 7-6 ka which continues today. In addition to the palaeoenvironmental reconstruction of the site amino acid racemisation was carried out on ostracod valves from the lake floor to assess the viability of such dating methods for playa lakes. This study found that pre-treatment with bleach (NaOCl) was useful in correcting slight reversing trends caused by a combination of environmental factors and with further work to gain a better understanding of such processes could become a valuable tool for age determination in such environments.