title: Discoidal impressions and trace-like fossils more than 1200 million years old.
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.
authors: Centre for Global Metallogeny, Department of Geology and Geophysics, University of Western Australia, Crawley, Western Australia 6009, Australia. brasmussen@geol.uwa.edu.au
authors: Birger
authors: B
authors: Rasmussen
authors: Stefan
authors: S
authors: Bengtson
authors: Ian R
authors: IR
authors: Fletcher
authors: Neal J
authors: NJ
authors: McNaughton
mesh_terms: D000818:Animals; D003460:Crystallization; D005580:Fossils; D019015:Geologic Sediments / Q000737:chemistry; D008674:Metals, Rare Earth; D009068:Movement; D009093:Mucus; D017640:Silicates; D013995:Time; D014904:Western Australia; D015040:Zirconium
chemical_list: D008674:Metals, Rare Earth; D017640:Silicates; C015370:monazite; C003784:zircon; D015040:Zirconium