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Published on: August 15, 2018
Discoidal impressions and trace-like fossils more than 1200 million years old
Birger Rasmussen1, Stefan Bengtson, Ian R Fletcher
1Centre for Global Metallogeny, Department of Geology and Geophysics, University of Western Australia, Crawley, Western Australia 6009, Australia. brasmussen@geol.uwa.edu.au
Abstract:
The Stirling Range Formation of southwestern Australia contains discoidal impressions and trace-like fossils in tidal sandstones. The various disks have previously been linked to the Ediacaran biota, younger than 600 million years old. From this unit, we report U-Th-Pb geochronology of detrital zircon and monazite, as well as low-grade metamorphic monazite, constraining the depositional age to between 2016 +/- 6 and 1215 +/- 20 million years old. Although nonbiological origins for the discoidal impressions cannot be completely discounted, the structures resembling trace fossils clearly have a biological origin and suggest the presence of vermiform, mucus-producing, motile organisms.
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