Was the Amadeus Basin of Central Australia a crucible for pre-Ediacaran macro-biotic evolutionary trials?

ABSTRACT

Vertical burrowing is a biological activity deemed to have evolved during the earliest Cambrian, the older soft-bodied fossils of the Ediacaran Period, that thrived between 575 and 541 Ma, seemingly being restricted to occupying the seafloor/ocean interface. Yet at two levels within the pre-Ediacaran sequence of the Amadeus Basin, central Australia, are vertical tubular features that have previously been reported as possibly of biogenic origin: a suite of such tubes occurs within the Areyonga Formation, dated at about 700 Ma, while two other tubular structures occur within the older Heavitree Formation that is perhaps 970–950 million years old. Should these structures prove, on re-examination, to indeed have been biologically formed, then vertical burrowing initially evolved possibly as much as 435 million years earlier than previously believed and these features would make the Amadeus Basin an isolated crucible of, seemingly, two evolutionary trials of vertical burrowing, albeit trials that ultimately failed for reasons that are discussed. Additionally, the same two stratigraphic levels each contain another structure that was also initially described as of biogenic origin, one being a possible body-fossil.

KEYWORDS:

• Amadeus basin
• Central Australia
• Neoproterozoic
• pre-Ediacaran
• Areyonga Formation
• Heavitree Formation
• vertical burrows
• evolutionary trials

Acknowledgments

Acknowledgement is made of the geologists who first mapped the Amadeus Basin over half a century ago and identified the “possible organic traces” that are re-visited herein with the aim of inducing a rethink on the restraints we place upon ourselves vis-à-vis the evolution of the earliest macroscopic lifeforms. Images from past publications, where not open access, are reproduced herein following receipt, with thanks, of written permission from their respective publishers. Drs Vic Gostin, Tony Milnes, Pat Rich and Jim Jago are thanked for encouraging publication, while the inclusion of constructive comments from Drs Malcolm Walter (on an early draft) and Sören Jensen improved the comprehensiveness of the final text. The ideas expressed herein, however, are solely those of the author.

Disclosure of potential conflicts of interest

No potential conflict of interest was reported by the author.