Summary: ..............................................................
Reassessing the evidence for the
earliest traces of life
Mark A. van Zuilen*, Aivo Lepland & Gustaf Arrhenius*
* Scripps Institution of Oceanography, University of California, San Diego,
La Jolla, California 92093-0236, USA
Geological Survey of Norway, Leiv Eirikssons vei 39, 7491 Trondheim, Norway
Institute of Geology, Tallinn Technical University, EE-0001 Tallinn, Estonia
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The isotopic composition of graphite is commonly used as a
biomarker in the oldest (>3.5 Gyr ago) highly metamorphosed
terrestrial rocks. Earlier studies on isotopic characteristics of
graphite occurring in rocks of the approximately 3.8-Gyr-old
Isua supracrustal belt (ISB) in southern West Greenland have
suggested the presence of a vast microbial ecosystem in the early
Archean1­4
. This interpretation, however, has to be approached
with extreme care5
. Here we show that graphite occurs abun-
dantly in secondary carbonate veins in the ISB that are formed at

Source: Arrhenius, Gustaf - Integrative Oceanography Division, Scripps Institution of Oceanography

Collections: Environmental Sciences and Ecology; Geosciences; Biology and Medicine