Publication: Tapices microbianos y estructuras sedimentarias asociadas en sistemas deposicionales evaporíticos de La Mancha: Un enfoque actualista
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2012
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Sociedad Geológica de España.
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Abstract
Los microorganismos presentes en tapices microbianos interaccionan con el medio originando estructuras sedimentarias características que difieren de las puramente abióticas, pero también de los estromatolitos típicos. Aunque en los ambientes evaporíticos modernos proliferan los tapices microbianos, las referencias a ellos son escasas. Este trabajo describe estructuras sedimentarias asociadas a tapices microbianos en lagunas evaporíticas (Lillo, Toledo). Éstas son variadas e incluyen, además de la precipitación bioinducida de minerales, formas de crecimiento irregulares en tapices, biolaminación, huellas de escape de gases, domos de gases, morfologías de los polígonos de desecación y su asociación a escape de gases, presencia de enrollamientos hacia arriba (curling up), tapices replegados (wrinkle structures), pseudoripples relacionados con formas de piel de elefante (elephant skin textures), ripples en parches (ripple patches), clastos de tapices (mat chips), estructuras fenestrales, etc. Se documenta también que algunas de estas estructuras se encuentran bien representadas en series evaporíticas terciarias, lo que indica que tienen potencial de preservación e invita a revisar interpretaciones previas. Estas estructuras sedimentarias se han descrito originalmente en series siliciclásticas del Arcaico por lo que su interpretación como facies biogénicas es, a veces, controvertida. Nuestras observaciones permiten ahondar en su origen biológico y añaden nuevos criterios para su interpretación.
Microorganisms in microbial mats interact with the environment leading to specific sedimentary structures (microbially induced sedimentary structures - MISS) that differ either from purely abiotic structures or from those typical of stromatolites. Although microbial mats are common in modern evaporitic environments, references to this type of structures formed under hypersaline conditions are scarce. In this paper, a variety of sedimentary structures associated with microbial mats in salt lakes (Lillo, Toledo) are described. In addition to a number of bioinduced precipitated minerals, the structures are varied and include irregular growth forms of the microbial mats, biolamination, traces of gas bubbling, trapping and doming, desiccation polygonal forms usually associated with gas bubbles and showing curling up edges, and wrinkle structures, pseudo-ripples and other shapes resembling elephant skin (old elephant skin), ripple patches, mat chips, fenestral fabrics, etc. Some of these structures are well represented in Tertiary evaporitic series, thus indicating that they have potential for preservation in rock record and points to reconsidering earlier interpretations of these evaporitic sequences. The new observations can increase knowledge on the biological origin of the microbially induced sedimentary structures and provide new criteria for their interpretation.
Microorganisms in microbial mats interact with the environment leading to specific sedimentary structures (microbially induced sedimentary structures - MISS) that differ either from purely abiotic structures or from those typical of stromatolites. Although microbial mats are common in modern evaporitic environments, references to this type of structures formed under hypersaline conditions are scarce. In this paper, a variety of sedimentary structures associated with microbial mats in salt lakes (Lillo, Toledo) are described. In addition to a number of bioinduced precipitated minerals, the structures are varied and include irregular growth forms of the microbial mats, biolamination, traces of gas bubbling, trapping and doming, desiccation polygonal forms usually associated with gas bubbles and showing curling up edges, and wrinkle structures, pseudo-ripples and other shapes resembling elephant skin (old elephant skin), ripple patches, mat chips, fenestral fabrics, etc. Some of these structures are well represented in Tertiary evaporitic series, thus indicating that they have potential for preservation in rock record and points to reconsidering earlier interpretations of these evaporitic sequences. The new observations can increase knowledge on the biological origin of the microbially induced sedimentary structures and provide new criteria for their interpretation.
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