Comparative biosedimentology of some terraced travertine deposits
- NASA, Moffett Field, CA (United States). Ames Research Center
The authors have compared several travertine spring systems representing a range of thermal regimes and geological settings. The goal is to derive a facies model for terraced travertine deposits that integrates biological influences on sedimentary fabric and microstructure. The springs chosen for comparison include Asta Spring (Upper Geyser Basin, Yellowstone; [le] 85 C), Angel Terrace (Mammoth Group, Yellowstone; [le] 72 C), and Big Horn Spring, Wyoming ([le] 56 C). At the highest temperatures microbial mats are absent and primary structures are dense, botryoidal masses of calcite exhibiting radial acicular fabrics. At intermediate temperatures a variety of mat types and associated sedimentary fabrics were observed, their distribution being correlated with temperature and flow velocity. Two types of current-oriented streamer fabrics were observed, a type at 72--74 C formed by the precipitation of aragonite on surfaces of a finely-filamentous bacterial species resembling Thiothrix, and a second type at 45--55 C, formed by aragonite blades associated with thin microbial mats dominated by Spirulina that appear to bind small dumbell-shaped crystals of aragonite. In quiet water at 45--50 C, microbial mats dominated by species of Phormidium formed tufted mats associated with ridged networks and open fenestral fabrics. At Big Horn Spring, a filamentous eukaryotic alga forms mats in lower terracette ponds at < 40 C. Moving down the system, algal-coated pisoids up to 1 cm. became abundant. Algal filaments were able to retain mm-sized pisoids on spillways, where they had become embedded in terracette faces. All of the biogenic fabrics noted above survive early diagenesis, and have been identified in Holocene and Pleistocene travertines.
- OSTI ID:
- 5929413
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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