title: Paleoarchean trace fossils in altered volcanic glass.
abstract: Microbial corrosion textures in volcanic glass from Cenozoic seafloor basalts and the corresponding titanite replacement microtextures in metamorphosed Paleoarchean pillow lavas have been interpreted as evidence for a deep biosphere dating back in time through the earliest periods of preserved life on earth. This interpretation has been recently challenged for Paleoarchean titanite replacement textures based on textural and geochronological data from pillow lavas in the Hooggenoeg Complex of the Barberton Greenstone Belt in South Africa. We use this controversy to explore the strengths and weaknesses of arguments made in support or rejection of the biogenicity interpretation of bioalteration trace fossils in Cenozoic basalt glasses and their putative equivalents in Paleoarchean greenstones. Our analysis suggests that biogenicity cannot be taken for granted for all titanite-based textures in metamorphosed basalt glass, but a cautious and critical evaluation of evidence suggests that biogenicity remains the most likely interpretation for previously described titanite microtextures in Paleoarchean pillow lavas.
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0225; hstaudigel@ucsd.edu.
authors.forename: Hubert
authors.initials: H
authors.lastname: Staudigel
authors.affiliation: Department of Earth Science and Centre for Geobiology, University of Bergen, 5007 Bergen, Norway; and.
authors.forename: Harald
authors.initials: H
authors.lastname: Furnes
authors.affiliation: Centre for Geobiology, University of Bergen, 5007 Bergen, Norway; and Africa Earth Observatory Network and Earth Stewardship Science Research Institute, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa.
authors.forename: Maarten
authors.initials: M
authors.lastname: DeWit
mesh_terms: D005075:Biological Evolution; D005580:Fossils / Q000382:microbiology* / Q000648:ultrastructure*; D005898:Glass / Q000032:analysis*; D049690:History, Ancient; D013019:South Africa; D018707:Volcanic Eruptions / Q000032:analysis*; D014904:Western Australia
keywords: Paleoarchean; astrobiology; biogeosciences; early life; ichnofossil