Format

Send to

Choose Destination
Proc Natl Acad Sci U S A. 2015 Nov 24;112(47):14518-21. doi: 10.1073/pnas.1517557112. Epub 2015 Oct 19.

Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon.

Author information

1
Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095; ebell21@ucla.edu tmark.harrison@gmail.com.
2
Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095;
3
School of Earth, Energy, and Environmental Sciences, Stanford University, Stanford, CA 94305.

Abstract

Evidence of life on Earth is manifestly preserved in the rock record. However, the microfossil record only extends to ∼ 3.5 billion years (Ga), the chemofossil record arguably to ∼ 3.8 Ga, and the rock record to 4.0 Ga. Detrital zircons from Jack Hills, Western Australia range in age up to nearly 4.4 Ga. From a population of over 10,000 Jack Hills zircons, we identified one >3.8-Ga zircon that contains primary graphite inclusions. Here, we report carbon isotopic measurements on these inclusions in a concordant, 4.10 ± 0.01-Ga zircon. We interpret these inclusions as primary due to their enclosure in a crack-free host as shown by transmission X-ray microscopy and their crystal habit. Their δ(13)CPDB of -24 ± 5‰ is consistent with a biogenic origin and may be evidence that a terrestrial biosphere had emerged by 4.1 Ga, or ∼ 300 My earlier than has been previously proposed.

KEYWORDS:

Hadean; carbon isotopes; early Earth; origin of life; zircon

Comment in

PMID:
26483481
PMCID:
PMC4664351
DOI:
10.1073/pnas.1517557112
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center