Searching for a Hadean biosphere using the detrital zircon record


Several lines of evidence suggest that terrestrial life may be as or more ancient than the early Archean. The chief difficulty in assessing early Earth’s environment – and thus the plausibility of an early biosphere – is the lack of a known rock record prior to 4.02 Ga. This earliest eon of Earth history (the Hadean) can at present be studied directly only by detrital minerals found in later sediments. The most well-studied suite of Hadean minerals is the Jack Hills detrital zircons (Western Australia), ranging to nearly 4.4 Ga in age.  Although these zircons formed in Hadean magmas, various isotopic, trace element, and mineral inclusion-based lines of evidence provide clues suggesting the incorporation of weathered supracrustal materials in some of these magmas.  We can use these samples to search for potential evidence of a Hadean biosphere or for conditions favorable to one.  In addition, carbonaceous mineral inclusions may provide evidence for Hadean carbon cycling: an isotopically light graphite inclusion in a 4.1 Ga zircon may provide evidence for life on Earth by 4.1 Ga. By more fully exploiting mineral inclusions and trace element chemistry, especially in Hadean-Archean zircons from sites other than Jack Hills, we can develop a better grasp on both the crustal composition and surficial environment at the dawn of Earth history.


I did my undergrad in geology at the University of South Carolina, Ph.D. in geochemistry at UCLA, Simons Collaboration on the Origins of Life postdoc fellowship at UCLA, and am now an assistant project scientist in the ion probe lab here at UCLA.


This seminar will be held using the video conferencing software, Zoom. If you would like the link, please email