Home » Dunes » The timing and cause of formation of dunes in the Cooloola Sand Mass

The timing and cause of formation of dunes in the Cooloola Sand Mass

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The Cooloola Sand Mass is a large coastal dune field located between Noosa and Tin Can Bay.

The dune field is made up mostly of parabolic dunes which are formed when a blow-out migrates inland through vegetation leaving a ridge with a parabolic shape behind – hence parabolic dunes. The scale of the dunes is hard to see on the ground as they are tree covered and appear as hills on the landscape with the biggest being four or more kilometres long and several hundred metres high. The Cooloola Sand Mass is well known to science because of the work of Cliff Thompson and his team describing massively thick soils (megapodzols up to 30 m thick) formed on the older dunes that are believed to be the thickest soils in the world.

Prof. Jamie Shulmeister and Prof. Allen Gontz examining an outcrop to select for OSL sampling (Photo: Jamie Shulmeister)

Thompson and Bill Ward also mapped the dunes and showed that there was a remarkable sequence from very young and small dunes near the coast, through very large dunes over 200m high and rainforest clad in the middle of the dune field to old degraded dunes on the western side of the dune field near Tin Can Bay.

Our new work (Ellerton et al., 2020), along with the ages recently published by Walker and associates (Walker et al., 2018) finally provides a complete time line for the dunes. The dune field is remarkably old with the oldest surface dunes dating to between 700,000 and 800,000 years (Cooloola and Awinya dunes of Ward). While some desert dunes in Africa are older, we believe these to be the oldest coastal dunes preserved anywhere on earth (allowing for K’gari to be a similar age). Combining evidence from the two papers, the main high dunes date to between 100,000 and 200,000 years old (Yankee Jack, Bowarrady, Garawongera dunes of Ward). Closer to the coast, the still impressive dunes date from 10,000 years old to currently active with younger dunes nested inside or west of the older dunes (Triangle Cliff, Station Hill and Cape dunes from Ward with a new series – Freshwater – identified by us (Patton et al., 2019)).

A quick examination of the ages shows that there are distinct periods when dunes formed. For the most recent series, in the last 10,000 years or so, there is a clear relationship between the formation of the younger dunes and the rise in sea-level at the end of the last ice age. What we believe happened was that as sea-level rose, the rising sea eroded old dunes and beaches in areas that are now under water. The sand released from this erosion was fed onto the beach. This allowed big dunes to be built off the shoreline. Continued rises in sea-level until about 6500 years ago caused wave after wave of dunes to migrate inland ahead of the coast (which was also moving west). When sea-level rise stopped the main dune formations stopped receiving new sand and finally ground to a halt. That did not entirely stop new dunes forming.

David Fink sampling for magnetics high on the bluff (Photo: Allen Gontz)

Cyclones, fires and smaller changes in sea-level triggered the formation of the smaller coastal dunes in the last few thousand years by disrupting coastal vegetation and/or feeding more sand onto the beaches. The timing of formation of the high dunes (e.g. Yankee Jack dunes) strongly suggest that these dunes were also formed when the sea-levels were at or even higher than the present day as they appear to date to the last interglaciation (warm period/high sea-level at c. 125,000-80,000 years ago) or even the penultimate interglaciation (around 200,000 years ago). 

In contrast, some of the older scientific work argued that dunes formed preferentially during ice ages because it was more arid in Australia. They suggested that weaker vegetation cover allowed dune activity to start. We can say with certainty that no dune systems at Cooloola are related to cold/arid periods such as the Last Glacial Maximum.

Finally, the oldest dunes are very old indeed. These date the first formation of the modern dune field. We have some ideas as to why the dune field may have started at about 750,000 years ago but we are still writing these ideas up and they need to be scientifically peer reviewed. Watch this space. We also have results being written up from K’gari and will report on that in a later issue.

Patton, N.R., Ellerton, D., Shulmeister, J. 2019. High-resolution remapping of the coastal dune fields of south east Queensland, Australia: a morphometric approach, Journal of Maps, 15:2, 578-589, DOI: 10.1080/17445647.2019.1642246

Ellerton, D., Rittenour, T., Shulmeister, J., Gontz, A., Welsh, K., Patton, N.R. 2020.  Mechanisms and environmental implications of coastal dune field development in south east Queensland, Australia. Geomorphology 354:000-000. April 2020

 I would also like to acknowledge the other major chronology paper from Cooloola recently published. By using the combined ages we got a better story than would have been possible from either study alone.

Walker, J., Lees, B., Olley, J., Thompson, C., 2018. Dating the Cooloola coastal dunes of South-Eastern Queensland, Australia. Marine Geology 398, 73-85.

Acknowledgements

We acknowledge the Kabi Kabi people on whose land we were working and the Butchulla people of K’gari. The core of this work is from the PhD thesis of Dan Ellerton. Work by another PhD student, Nicky Patton, is also important. Lots of students and colleagues have helped with the work. Staff at Queensland Parks have been extremely helpful and supportive over the life of the project. Thanks to all.

Article submitted by Jamie Shulmeister


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