Precambrian biomarkers convey invaluable information
about the early evolution of life, ancient ecosystems, redox
conditions, climate and depositional environment and
prospective petroleum systems. They are however thermally
unstable, easily obliterated by contamination and thus
extremely difficult to find. This is particularly true if
conditions favourable for biomarker preservation had to
prevail for more than 2.5 billion years – the prerequisite for
finding Archaean biomarkers. Many organic geochemists
abandoned this hope after original discoveries of Archaean
biomarkers proved to be of younger origin [1,2] but our study
of ca. 550-825 Ma old sediments from the Centralian
Superbasin now shows that biomarkers can be preserved in
distinctive pockets in seemingly barren areas, even if sections
are metamorphosed in parts. Most Centralian sections seem
empty. Yet, eventually we identified intervals with preserved
biomarkers in three drill cores. A detailed investigation of 825
Ma sediments in drill core Mt Charlotte-1 revealed maturity
variations that are most likely due to hydrothermal influence
and in turn control the hydrocarbon preservation. Sediments
might appear metamorphosed after localized, subtle alteration
by hydrothermal fluids but protected intervals can still contain
biomarkers. The same might be true for Archaean sediments
and we might still find those protected intervals with
indigenous biomarkers that allow us to glimpse the early life
on earth
