Ion microprobe U-Pb dating of zircons extracted from a narrow tuff band in the Lower Cambrian Heatherdale Shale of South Australia produced an age of 526 ± 4 Ma (95% confidence limits). Local and regional trilobite and archaeocyathan evidence indicates that the tuff ìs latest Atdabanian or Botomian. The tuff shortly predates the onset of the Delamerian Orogeny.
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Cooper et al. (1992) studied this question.
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