"The age turned out to be more than a billion years younger than the enclosing quartzite,” said co-author Birger Rasmussen, adjunct professor at the University of Western Australia. “The burrows could therefore have been made by animals.”
https://www.physicalsciences.ucla.edu/g ... e-mystery/
But how can animals burrow through hard quartzite? The answer was given by microscopic investigations, which showed that the grains had first separated at contact surfaces, resulting in a friable matrix, and then been fused again through later deposition of quartz, returning the rock to the state of hard quartzite.
“A similar process produced the stuff of the standing stones of Stonehenge,” Runnegar said.
A window in time had thus been opened to enable burrowing, the researchers report. Through comparisons with surrounding sedimentary strata, the scientists could date this window to about 40 million years ago, during the Eocene epoch of Earth’s history.
“Most likely, the traces were made by crustaceans, which invaded southwestern Australia during a short-lived marine transgression associated with the opening of the Southern Ocean,” said senior author Stefan Bengtson, professor emeritus and paleontologist at the Swedish Museum of Natural History.
“These trace fossils in the ‘wrong’ rocks have been a mystery for half-a-century,” Bengtson said. “We are glad to have been able to demonstrate geological processes that resolve this conundrum.”
Maybe it was these guys???
Scientists have described a new species of the crayfish genus Cherax from the Murray-Darling Basin in eastern Australia.
“We’d heard rumours from landholders and river-users that there was a different and larger yabby living in the Barmah Forest — little did we know it would take so long to track it down,” said co-author Dr. Tarmo Raadik from the Arthur Rylah Institute for Environmental Research and Museums Victoria.
The swamp yabby looks similar to the well-known and widespread common yabby, , but is much larger and has uniquely shaped broad claws.
The species is not found in permanent aquatic habitats such as streams or billabongs, spending the majority of its time in extensive, terrestrial, burrow networks containing some water, in ephemerally wet habitats such as drainage lines, roadside drains, depressions, swamps and cleared areas of pasture in lowland to foothill areas.
It is occasionally found in stream habitats but only during large flood events when burrow systems are inundated.
“The exciting discovery of the swamp yabby is a significant biodiversity achievement, which adds to the wealth of important information used to manage and protect Victoria’s waterways and its aquatic creatures that call them home,” said James Todd from the Department of Environment, Land, Water and Planning, a state government department of Victoria.
“It’s the first time in 80 years that a new yabby species in the Murray-Darling Basin system has been formally described, making the swamp yabby only the third species known to naturally occur in the Basin.”
“It’s found in deep clay soil burrows in northern Victoria’s Goulburn, Broken and Ovens River catchments, and as far north as Deniliquin in New South Wales.”
http://www.sci-news.com/biology/swamp-y ... ce+News%29