Honours Thesis Abstract
HOLOCENE EVOLUTION OF A BARRIER ESTUARY,
LAKE ILLAWARRA, NEW SOUTH WALES
Craig R. Sloss
University of Wollongong, NSW
2001 AIG Honours Bursary Winner
The Holocene evolution of Lake Illawarra, New South Wales, reflects the influence of
the post-glacial marine transgression and sea level highstand on sedimentation within
the developing barrier estuary. Twenty-six vibracores from the fluvial-estuarine, central
lagoon and marine-estuarine environments, in conjunction with extensive seismic
traverses across Lake Illawarra formed the basis of this investigation. Fifty-five amino
acid racemisation (AAR) analyses, calibrated by radiocarbon ages on Anadara trapezia
(680070 a BP, SUA-3102) and Notospisula sp. (580080 a BP, SUA-3203), obtained
from Lake Illawarra provide the chronostratigraphic framework for elucidating the
evolution of this lagoon. The resulting aminostratigraphy has enabled a detailed
chronostratigraphic model of Holocene sedimentation within the barrier estuary of Lake
Illawarra to be constructed. This model indicates that the Holocene highstand in the
Illawarra region was reached some time before to 6600a and was approximately 2 m
higher than present. The Holocene transgression is represented by an incursion of
marine sand within the incised valley system, which changed to a quieter water
environment with good circulation as sea level rose. As the Windang sand barrier grew,
especially after ca.3000 a when Holocene sea level fell to near present level, the
environment changed to a low energy estuarine system. Knowledge about the
stratigraphic evolution of Lake Illawarra will assist in providing a better understanding
of past depositional processes operating within the lagoon, as well as for developing a
model for future sedimentary trends in estuarine environments along the Illawarra
coastline. A better understanding of depositional processes will allow appropriate
management of estuarine environments in response to stable or fluctuating sea-level, as
well as the development of management plans in response to adverse environmental
conditions caused by the impact of urbanisation and industrialisation within the
Illawarra region.