Biofilms, texturas y composición isotópica de travertinos actuales y fósiles, Alhama de Almería-Alicún (Provincia de Almería)

Resumo

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 (C13VPDB and O18VPDB) 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 C13VPDB (from -2,13 to -2,04) than the equivalent fossil facies (C13VPDB from -1,40 to -1,05). These data highlight the biogenic influence on both materials. The O18VPDB 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).