Ancient mud flats not that old: geologists
Australian geologists studying what they thought was an ancient inland floodplain in southern NSW have been shocked to discover that it's actually less than 50 years old.
The finding highlights the often catastrophic impact European agriculture and forestry has had on the fragile Australian countryside, the researchers say.
"There's little doubt modern Australians have underestimated the extent of change we have inflicted on our landscape," says Dr Peter Wallbrink, a scientist from CSIRO Land and Water and member of the team studying the floodplain. "In some cases the rates are staggering".
"Deposits of silt and sediment on the lower floodplain of the Murrah appeared to us to be at least a couple of hundred years old - until we began to test their composition and age," Dr Wallbrink said.
The team was able to date the soil by looking at the radioactivity of the different sedimentary layers. Nuclear testing in the 1950s and 60s left a telltale radioactive layer in the soil around the world, giving a maximum age for all sediments deposited above.
Scientists are now looking to identify the chief source of the soil loss by comparing the relative contributions made by agriculture and forestry in the catchment area.
This understanding will be vital in devising the best strategies for farmers, foresters and land managers to combat future large-scale erosion and deposition events and improve water quality and sustainability, says Dr Wallbrink.