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6 - Modern Mat-Building Microbial Communities: a Key to the Interpretation of Proterozoic Stromatolitic Communities
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- By Beverly K. Pierson, University of Puget Sound, John Bauld, Bureau of Mineral Resources, Richard W. Castenholz, University of Oregon, Elisa D'Amelio, Ames Research Center, David J. Des Marais, Ames Research Center, Jack D. Farmer, University of California, John P. Grotzinger, Massachusetts Institute of Technology, Bo Barker Jørgensen, University of Aarhus, Douglas C. Nelson, University of California, Anna C. Palmisano, Ivorydale Technical Center, J. William Schopf, University of California, Roger E. Summons, Bureau of Mineral Resources, Geology and Geophysics, Australia, Malcolm R. Walter, M. R. Walter Pty. Ltd, David M. Ward, Montana State University
- Edited by J. William Schopf, University of California, Los Angeles, Cornelis Klein, University of New Mexico
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- Book:
- The Proterozoic Biosphere
- Published online:
- 04 April 2011
- Print publication:
- 26 June 1992, pp 245-342
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- Chapter
- Export citation
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Summary
Introduction
Modern microbial mats are structurally coherent macroscopic accumulations of microorganisms. Mats are widely distributed on earth. They are found in a surprisingly large number of diverse environments from the equatorial zones to both polar regions. They vary in size from extensive terrestrial and hypersaline mats that cover areas several square kilometers in extent to minute mats only a few square centimeters in area found in small thermal springs. They vary in thickness from massive accumulations measured in meters, such as those in the Persian Gulf and the Red Sea region, to thin films less than a few millimeters in thickness. In addition to being highly varied in size, modern microbial mats are also very diverse in morphology, community structure, and physiological characteristics. What do such mats have in common? Under what conditions do they form? What is the basis of their diversity? What insight do they provide, if any, to the interpretation of the widespread stromatolites of the Proterozoic?
A Terminology
Microbial mats are accretionary cohesive microbial communities which are often laminated and found growing at the sediment-water (occasionally sediment-air) interface. Most mats stabilize unconsolidated sediment. The mats are comprised of the various microorganisms that accumulate along with their metabolic products. The most conspicuous of these products is usually a copious amount of extracellular polysaccharide which helps hold the cells together to form a cohesive structure.