A recent investigation conducted by Curtin University has examined the intricate evolution of two renowned landmarks in Western Australia, charting their changes over millennia and providing insights into their potential future. Researchers gathered sediment samples from various points along the coastline of Perth, its waterways, and even the ocean floor to observe the transformations that took place as sea levels rose significantly over the ages.
A recent investigation conducted by Curtin University has examined the intricate evolution of two renowned landmarks in Western Australia, charting their changes over millennia and providing insights into their potential future.
Experts from the Timescales of Mineral Systems Group within the School of Earth and Planetary Sciences extracted sediment samples from several sites along Perth’s coastline, as well as its rivers and the ocean floor, to monitor alterations caused by rising ocean levels over thousands of years.
The study, led by Dr. Andreas Zametzer, revealed that the dive teams discovered specific mineral grains offshore, which highlighted the complex geological chronicles of Rottnest Island (known as Wadjemup in Noongar) and the Swan River (referred to as Derbarl Yerrigan).
The ancient mineral grains found near Rottnest Island were estimated to be as old as 3.6 billion years.
These grains can also be traced back to the present-day Swan River estuary and the Avon River tributary, where they were transported and deposited thousands of years ago.
“Perth sits upon a continental margin that is currently sinking,” stated Dr. Zametzer.
“Until approximately 6,500 years ago, Rottnest Island was part of a peninsula—much like we observe in the Shark Bay area—and since it remains part of this inundated continental margin, the sea between Perth and Rottnest is mostly less than 20 meters deep.”
“We’ve established that the mouth of the Swan River used to be situated north of Rottnest Island, prior to its current location.”
Dr. Zametzer expressed surprise at discovering the ancient mineral grains so far offshore.
“We would have anticipated that the grains would have eroded and moved away due to the tumultuous, high-energy conditions from waves and tides,” he noted.
“However, the unique mineral characteristics associated with the river remain intact, despite the extensive changes in sea level and the reworking of the continental shelf over thousands of years.
“This off-coast imprint of the river system gives us confirmation of the historical context of the coast.”
Dr. Zametzer emphasized the significance of understanding how coastlines have adapted and transformed over time to better prepare for the implications of rising sea levels in the future.
“It’s quite astonishing to realize the speed at which certain geological processes occur as sea levels continue to rise relentlessly.”
‘When the river meets the sea: Transport and provenance in a long-lived estuary’ was published in Basin Research.
