Doctor of Philosophy
School of Earth and Environmental Sciences
Oliver, Thomas Sidney Newton, Holocene depositional history of three coastal sand ridge plains, southeastern Australia, Doctor of Philosophy thesis, School of Earth and Environmental Sciences, University of Wollongong, 2016. http://ro.uow.edu.au/theses/4644
Holocene coastal sand ridge plains, also known as prograded barriers or strandplains, occur on many coastlines around the world. During the 20th century and into the 21st century, these coastal landforms have been investigated in order to understand the timing and mode of their emplacement, and their potential as paleoenvironmental records. Radiocarbon dating of coastal sand ridge plains in southeastern Australia has made a significant contribution to our knowledge of the Holocene deposition of these environments. This study examines three coastal sand ridge plains in southeastern Australia: Moruya (Bengello Beach), Wonboyn and Callala Beach. The Holocene depositional history of these sites was investigated using optically stimulated luminescence (OSL) dating of aeolian sands from individual ridges to construct a chronology of progradation. Ground penetrating radar (GPR) was used to image subsurface structures, and airborne Light Detection and Ranging (LiDAR) data provided a detailed picture of the morphology of each site. LiDAR data also enabled the determination of precise ridge heights and the calculation of aeolian sediment volumes. OSL dating at each site demonstrated that progradation proceeded at linear rates from ~7500 years ago to present. The OSL chronology of progradation at Moruya was a significant revision to the previously accepted pattern implied by radiocarbon dating. The age of progradation commencement around ~7500 years ago at each site corresponds closely with cessation of the post-glacial marine transgression on this coastline. Rates of progradation at Moruya and Wonboyn were ~0.3 m/yr, while Callala Beach prograded at ~0.1 m/yr. The Moruya embayment had the highest average aeolian sediment accumulation rate of the three sites at ~3600 m3/yr, Wonboyn had a slightly lower value of ~1760 m3/yr and Callala Beach had the lowest average sediment delivery at ~650 m3/yr. GPR data collected in shore normal transects across each site demonstrated that each barrier has built seawards in increments with a series of preserved storm beachfaces separated by accumulated material. The process of ridge building indicated by the GPR imaged reflectors appears similar to the process of incipient ridge development observed at Moruya in beach profiling over the past ~40 years; where ridge building occurs during post-storm recovery of the beachface. Each site is dominated by a modern foredune which is substantially higher than all other landward ridges. At Moruya, GPR across this foredune reveals a series of landward dipping reflectors indicating the landward cascading of aeolian sediments not observed on any other ridges. These foredunes appear to represent an unprecedented degree of dune development on these barriers. This reconstruction of Holocene deposition at Moruya, Wonboyn and Callala Beach may inform future management of sandy coastlines as it quantifies the volumes of sediment involved in coastal progradation in southeastern Australia.