Possible microbial effects on stable carbon isotopes in hot-spring travertines
- Univ. of Wales Cardiff (United Kingdom). Dept. of Earth Sciences
- Univ. of East Anglia, Norwich (United Kingdom). School of Environmental Sciences
Recent and older (early Holocene to Pleistocene) hot-spring travertine carbonates from central Italy have two distinctive macrofabrics, crystalline crusts and shrubs. Crystalline crusts are laminated slope deposits that formed abiotically following CO{sub 2} degassing from spring water. The formation of shrub travertine--irregular, dendritic precipitates from pool environments--is controversial and has been attributed to both abiotic and microbial processes. Oxygen isotope variation in the authors` travertines can be explained by abiotic processes, mainly CO{sub 2} degassing. In contrast, the carbon isotope data cannot be wholly explained by abiotic CO{sub 2} degassing invoked in earlier studies. Because photosynthesis is known to preferentially remove {sup 12}C, leaving ambient waters enriched in {sup 13}C, this fractionation should be recorded in {delta}{sup 13}C values of microbially influenced travertine. The shrub carbon isotope values are between 0.5% and 6.0% larger than values for associated abiotic precipitates, and this difference is probably caused by microbial activity. These isotope data support previous visual evidence that some shrub fabrics are microbially influenced.
- OSTI ID:
- 277594
- Journal Information:
- Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes, Journal Name: Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes Journal Issue: 3 Vol. 66; ISSN JSRAEA; ISSN 1073-130X
- Country of Publication:
- United States
- Language:
- English
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