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Fossilization processes in siliceous thermal springs: trends in preservation along thermal gradientsTo enhance our ability to extract palaeobiological and palaeoenvironmental information from ancient thermal spring deposits, we have studied the processes responsible for the development and preservation of stromatolites in modern subaerial thermal spring systems in Yellowstone National Park (USA). We investigated specimens collected from silica-depositing thermal springs along the thermal gradient using petrographic techniques and scanning electron microscopy. Although it is known that thermophilic cyanobacteria control the morphogenesis of thermal spring stromatolites below 73 degrees C, we have found that biofilms which contain filamentous thermophiles contribute to the microstructural development of subaerial geyserites that occur along the inner rims of thermal spring pools and geyser effluents. Biofilms intermittently colonize the surfaces of subaerial geyserites and provide a favoured substrate for opaline silica precipitation. We have also found that the preservation of biotically produced microfabrics of thermal spring sinters reflects dynamic balances between rates of population growth, decomposition of organic matter, silica deposition and early diagenesis. Major trends in preservation of thermophilic organisms along the thermal gradient are defined by differences in the mode of fossilization, including replacement, encrustation and permineralization.
Document ID
Document Type
Reprint (Version printed in journal)
Cady, S. L. (NASA Ames Research Center Moffett Field, CA United States)
Farmer, J. D.
Date Acquired
August 22, 2013
Publication Date
January 1, 1996
Publication Information
Publication: Ciba Foundation symposium
Volume: 202
ISSN: 0300-5208
Subject Category
Geosciences (General)
Distribution Limits
NASA Discipline Exobiology
Review, Tutorial