Publication: Biofilms, texturas y composición isotópica de travertinos actuales y fósiles, Alhama de Almería-Alicún (Provincia de Almería)
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2012
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Sociedad Geológica de España
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Abstract
El estudio de travertinos actuales en Alicún (Almería), con facies tobáceas asociadas, ha permitido observar la relación de facies laminares travertínicas (costras) con biofilms. Mediante óptica y electrónica de barrido sobre muestras fijadas con glutaraldehido y tetróxido de osmio,se han observado cianobacterias (principalmente filamentosas), bacterias y diatomeas formando dichos biofilms. La costra se compone de calcita de bajo contenido en Mg y dolomita, yeso y barita como minerales accesorios. Se ha comparado la composición isotópica de la calcita VPDB y O18 VPDB) de los materiales actuales: tobas de briofitas y los citados travertinos,con travertinos próximos explotados como roca ornamental,con texturas cristalinas fibrorradiadas similares. Estos últimos travertinos están relacionados con manifestaciones hidrotermales de Alhama de Almería y están asociados con facies tobáceas. También se han comparado con facies tobáceas, de la misma zona,relacionadas con procesos fluviales más modernos. Los travertinos de la fuente actual muestran un C13 VPDB ligeramente inferior VPDB: de - 2,13 a -2,04) a las facies equivalentes fósiles: (δC13 VPDB : -1,40 a -1,05). Estos valores ponen de manifiesto la influencia biogénica en ambos materiales. El δO18 VPDB de los travertinos de la fuente, de -10,9 a -9,95 es ligeramente inferior al de los travertinos antiguos (-7,84 a -7,54).
The study of recent travertines at a spring in the village of Alicún (Almería) associated with tufa facies,has revealed the relationship of laminar travertine facies (travertine crusts) with biofilms. Using microscopic techniques, optical microscopy and scanning electron microscopy of samples fixed in glutaraldehyde and osmiun tetroxide, cyanobacteria, bacteria and diatoms have been observed in these biofilms,. The crust consists of low-Mg calcite, with dolomite, gypsum and barite as accessory minerals. The isotopic composition of calcite (δC13 VPDB and δO18 VPDB) of recent materials; bryophyte tufas and the aforementioned travertines, has been compared with the composition of nearby travertine quarried as ornamental rocks with similar crystalline fibroradiate textures. These travertines are related to hydrothermal manifestations of Alhama de Almería and are associated with tufa facies. They have also been compared with tufa facies of the same area, related to modern fluvial processes. The travertines at the current spring show a slightly lower δC13 VPDB (from -2,13 to -2,04) than the equivalent fossil facies ( δC13 VPDB from -1,40 to -1,05). These data highlight the biogenic influence on both materials. The δO18VPDB of the travertines located at the recent spring -10.9 to -9.95, are slightly lower than the older travertine values (from -7,84 to -7,54).
The study of recent travertines at a spring in the village of Alicún (Almería) associated with tufa facies,has revealed the relationship of laminar travertine facies (travertine crusts) with biofilms. Using microscopic techniques, optical microscopy and scanning electron microscopy of samples fixed in glutaraldehyde and osmiun tetroxide, cyanobacteria, bacteria and diatoms have been observed in these biofilms,. The crust consists of low-Mg calcite, with dolomite, gypsum and barite as accessory minerals. The isotopic composition of calcite (δC13 VPDB and δO18 VPDB) of recent materials; bryophyte tufas and the aforementioned travertines, has been compared with the composition of nearby travertine quarried as ornamental rocks with similar crystalline fibroradiate textures. These travertines are related to hydrothermal manifestations of Alhama de Almería and are associated with tufa facies. They have also been compared with tufa facies of the same area, related to modern fluvial processes. The travertines at the current spring show a slightly lower δC13 VPDB (from -2,13 to -2,04) than the equivalent fossil facies ( δC13 VPDB from -1,40 to -1,05). These data highlight the biogenic influence on both materials. The δO18VPDB of the travertines located at the recent spring -10.9 to -9.95, are slightly lower than the older travertine values (from -7,84 to -7,54).