成人大片

A team of scientists, led by the 成人大片鈥檚 Associate Professor John Tibby, has confirmed that the lower River Murray was not an estuary in the mid-Holocene period (more than 7000 years ago) 鈥� reinforcing scientific evidence likely to influence important river management policy decisions.

Their new paper, published in the Nature journal聽聽was produced in response to claims made in a 2020 paper by University of Sydney鈥檚 Dr聽Anna Helfensdorfer聽and co-authors 鈥� which gained considerable traction during the past year through聽.

Flinders University Strategic Professor in Coastal Studies, Professor Patrick Hesp, says the consequences that could lead from river policy makers following those fresh claims about the River Murray鈥檚 history would be significant.

鈥淭he authors of the 2020 paper claim their findings should result in a re-evaluation of south-eastern Australian climate reconstructions from marine sediments off the River Murray mouth 鈥� but this is a series of propositions we reject,鈥� says Professor Hesp.

The authors of the new paper published in聽Scientific Reports, say multiple lines of evidence show that the Lower Lakes and lower River Murray were predominantly freshwater and any claims that they were marine and estuarine in the mid-Holocene are based on unrealistic assumptions.

鈥淭here is a wide range of evidence laid down in sediments in and around Lake Alexandrina that shows that the lakes were fresh 7000 years ago. Importantly, lower sea level made it physically impossible for an estuary to form in the lower River Murray as has been suggested.鈥�Lead author, Associate Professor John Tibby, the 成人大片

Lead author, Associate Professor John Tibby said: 鈥淭here is a wide range of evidence laid down in sediments in and around Lake Alexandrina that shows that the lakes were fresh 7000 years ago. Importantly, lower sea level made it physically impossible for an estuary to form in the lower River Murray as has been suggested.鈥�

Archaeological investigations led by Flinders University archaeologist, and Kaurna and Ngarrindjeri man, Dr Christopher Wilson also demonstrate that indigenous people were reliant on freshwater resources such as freshwater mussels at least 86 km up the Murray River from c. 8400 years ago to the time of European occupation. This evidence largely negates the possibility of the River being estuarine.

The new paper鈥檚 co-authors, spanning several scientific disciples, also include Dr Graziela Miot da Silva and Professor Robert Bourman, with Professor Colin Murray-Wallace, Associate Professor Luke Mosley, Deborah Haynes, Dr Deirdre Ryan and Dr Antonio Belperio.

鈥淟akes Alexandrina and Albert are currently managed to keep them fresh. This approach is consistent with their predominantly fresh history,鈥� Associate Professor John Tibby said.

The new paper identifies multiple lines of physical evidence for freshwater in the lower River Murray and Lower Lakes during the mid-Holocene period that are diametrically opposed to the inferred significant marine incursion modelled by Helfensdorfer et聽al.

The research found no definitive evidence exists for estuarine deposition of Holocene clays in the Murray Gorge, and the supposed 鈥渆stuary鈥� clays were deposited by rapid fluvial aggradation of fine-grained sediments between 10,000 and 7000 years ago.

The scientists say it is 鈥榥ormal鈥� for slow flowing, extremely low gradient, lowland rivers to transport clays and silts as suspended load 鈥� and that no marine or estuarine molluscs, dinoflagellates or diatoms are reported from the clays at Monteith.

The paper鈥檚 conclusions state: 鈥淲hile it was suggested that higher salinities could have aided clay flocculation and deposition, this process can happen in slow moving freshwater, while dense reed beds may have aided sediment trapping. Indeed, the deposition of clays before, and after the inferred mid-Holocene estuary demonstrates that this can occur in the absence of elevated salinity.鈥�

The paper is part of a larger piece of research underway into the history of the lower River Murray lakes.

"A large mid-Holocene estuary was not present in the lower River Murray, Australia" (DOI 10.1038/s41598-021-90025-9) is published online by Scientific Reports and freely available online at聽.

The study was funded by the Australian Research Council鈥檚 Centre for Biodiversity and Heritage (CABAH) and its Discovery program. The study region is within the聽Yurluwar -ruwe聽(traditional lands and waters) of the Ngarrindjeri people and was undertaken with the approval of the Ngarrindjeri Regional Authority.