Microbially-induced sedimentary structures in Archean sandstones; a new window into early life

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doi: 10.1016/j.gr.2006.10.004
Authors:Noffke, Nora
Author Affiliations:Primary:
Old Dominion University, Department of Ocean, Earth and Atmospheric Sciences, Norfolk, VA, United States
Volume Title:Gondwana Research
Source:Gondwana Research, 11(3), p.336-342. Publisher: Elsevier on behalf of International Association for Gondwana Research, Amsterdam and Kochi, International. ISSN: 1342-937X
Publication Date:2007
Note:In English. 55 refs.; illus.
Summary:Until now, the most valuable information on the early life on the Archean Earth derived from bacterial fossils and stromatolites preserved in precipitated lithologies such as chert or carbonates. Also, shales contain complex biomarker molecules, and specific isotopes constitute an important evidence for biogeneicity. In contrast, because of their low potential of fossil preservation, sandstones have been less investigated. But recent studies revealed a variety of 'microbially induced sedimentary structures - MISS' that differ greatly from any other fossils or sedimentary structures. "Wrinkle structures", "multidirected ripple marks", "biolaminites", and other macrostructures indicate the former presence of photoautotrophic microbial mats in shallow-marine to tidal paleoenvironments. The MISS form by the mechanical interaction of microbial mats with physical sediment dynamics that is the erosion and deposition by water agitation. The structures occur not only in Archean tidal flats, but in equivalent settings throughout Earth history until today. MISS are not identified alone by their macroscopic morphologies. In thin-sections, the structures display the carpet-like fabrics of intertwined filaments of the ancient mat-constructing microorganisms. Geochemical analyses of the filaments proof their composition of iron minerals associated with organic carbon. In conclusion, microbial mats colonize sandy tidal settings at least for 3.2 Ga years. Therefore, Archean sandstones constitute an important archive for the exploration of early life.
Sections:Petrology
Subsections:Sedimentary rocks
Subjects:Algal mats; Algal structures; Archean; Biogenic structures; Clastic rocks; Coastal environment; Depositional environment; Life origin; Microorganisms; Paleoenvironment; Precambrian; Sandstone; Sedimentary rocks; Sedimentary structures; Sedimentation; Tidal flats
Abstract Numbers:07M/1783
Record ID:2007110566
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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