Coastal Dunes - Some Reflections

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I have long had a thing about coastal dunes; perhaps it is in my genes? My mother’s family owned property in Sandridge Street, Bondi, and I grew up on the sand plain of Rose Bay. As an undergraduate I had the great joy of digging a pit in our tiny backyard to discover the structure of the iron-humus podzol soil profile—it was fascinating stuff.

Life became more serious once I selected Port Stephens-Myall Lakes as a study area for my honours year in 1960. Time to escape life in the city for wanderings around the active and stabilised dune fields that had received little previous attention. It proved to be a treasure trove of dune types that kept myself and colleagues quite busy for years after and hopefully will continue to attract interest.

These early dune meanderings were supported by three things: first the mentorship of Trevor Lang-ford-Smith and Joe Jennings; second the availability of air photos to use both for mapping and ground-truthing; and third the discovery of inspiring literature on sand dunes in general and coastal types in particular. I have previously discussed the role of mentors. Geomorphology at that time required careful analysis of imagery, which amongst other things, enabled me to converse with interested locals who had never visualised their country from that perspective. But it was the writing of a few dune researchers that made me think most about what the study of these dunefields had to offer.

I have already mentioned Joe Jennings; he had just published an extraordinary study of the coastal dunes of King Island in the Bass Strait. But it was the work of W.S. Cooper on the dunes of the coast of Oregon and Washington that really got me going (1958, Memoir, Geological Society of America, No.72). I found a copy in the library of the Mines Department in Sydney and devoured it. Cooper started field work in the area in 1933 and assembled an enormous amount of biophysical data on dune type and formation. His work expanded on the great desert dune research by R.A. Bagnold (1941) to which we all pay tribute in any work on dune processes. However, Cooper took issue with some of Bagnold’s findings on the stability of mobile transverse dunes, which Bagnold considered could not persist in a mobile state. However, Cooper did not think that such dunes, although stable as free-moving forms, could not survive colonisation by vegetation. In my thesis (and later publication) I had the temerity to take issue with him on this having mapped the forested “transverse” dunes near Seal Rocks (Thom et al., 1992, Coastal Geomorphology and Quaternary Geology of the Port Stephens-Myall Lakes area, Biogeography and Geomorphology, ANU, Monograph, No. 6). I corresponded with him in 1961 and sent him air photos, but it did not convince him. This still remains an issue.

One of the joys of working on coastal dunes has been an association with those who have undertaken dune research in Australia and overseas. It has been very satisfying to see how these scientists have added to our knowledge of dune processes and evolution. In particular, I refer to Pat Hesp, Brian Lees and Ken Pye. Both Pat and Brian were at Sydney University when I was on staff. Pat’s initial work was on foredunes but this has expanded into the study of various dune types on several continents. He continues to prosper from his base at Flinders. Brian has retired as Professor at ADFA, but it was pleasing to see him as an author on a paper on dating of Cooloola coastal dunes (Walker, et al., Marine Geology, 2018, 398). Ken Pye is based in the UK and worked in the late 70s-80s on the massive dunes of north Queensland. I had many pleasant hours while on sabbatical at Cambridge in 1980 discussing his work, and encouraged him to publish in a volume I edited in 1984 (Pye and Bowman, 1984 in Coastal Geomorphology in Australia). This paper further expanded on a hypothesis that was initially developed by Cooper and taken up by me in 1978, namely that the postglacial marine transgression played a part in transgressive dune initiation. Brian in 2006 in Journal of Coastal Research referred to this idea as the Cooper-Thom hypothesis and showed its shortcomings (see also in his recent Marine Geology paper with Walker et al.).

One of my dreams in the 60s and 70s was how to date sand dunes. I used different techniques: geomorphic position on dated sand barriers, soil profile development and radiocarbon dating of buried organics. But the arrival of TL and OSL dating of sand grains opened up a new world to understanding dune chronology both in Australia and overseas. It was a pleasure to see the work of Markewich and colleagues in 2015 (Aeolian Research, 17) citing my old field study of dunes and other features based on my PhD research in South Carolina. David Price and his team at Wollongong pioneered several important studies of coastal sites, and using the TL technique Pat Hesp, Ted Bryant and I put together a revised chronology of dune ages from the Port Stephens area (Palaeo 3, 1994, 111). But the arrival of OSL has generated several more substantive studies especially of the dunes of SE Queensland (Walker, et al., 2018; and Brooke et al., 2015, Continental Shelf Research, 105).

I have recently collaborated with Tom Oliver (formerly Wollongong, now ADFA) on dating dune sands around my old home area of eastern Sydney. Tom and colleagues have been using OSL to develop chronologies of coastal sites in SE Australia over recent years (see Oliver, et al., 2018, Palaeo 3). I sampled building sites with podzolised soils. The story from this work when published will be subject to a future blog. It is just amazing how far dune research has come when you can go back to a place and with new eyes and new techniques build on work done decades ago.

 

Bruce Thom  

 

Words by Prof Bruce Thom. Please respect the author’s thoughts and reference appropriately: (c) ACS, 2018, posted 12 August 2018, for correspondence about this blog post please email austcoastsoc@gmail.com 

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