Publication: Contexto geológico y características petrofísicas de las rocas carbonáticas del Cerro de la Rosa (Toledo)
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Publication Date
1993
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Sociedad Geológica de España
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Abstract
La investigación sobre los materiales pétreos utilizados en la Catedral de Toledo ha permitido la localización de los afloramientos que suministraron rocas carbonáticas (dolomías) durante las primeras fases de la construcción de la Catedral (siglos XIII a XV). Dichos afloramientos se sitúan en el Cerro de la Rosa, área en la que a principios de este siglo se encontraron restos de fauna
marina cuya datación fue objeto de controversias, condicionando posteriores interpretaciones paleo geográficas en la Cuenca del Tajo. Uno de los resultados de este estudio es que el Cerro de la Rosa está formado por depósitos de edad Cretácico superior que consisten en facies carbonáticas, carbonáticas-terrígenas y margosas con restos de fauna marina. Sobre estos depósitos se sitúan en discordancia niveles clásticos continentales de edad Paleó geno inferior. Este esquema estratigráfico básico para el Cerro de la Rosa permite aclarar la controversia suscitada respecto a este área. El análisis petrográfico y petrofísico de las dolomías del Cerro de la Rosa permite distinguir tres tipos esenciales (dolomías homogéneas, arenosas y nodulosas) cuya respuesta ante los ensayos de absorción, capilaridad, desorción, durabilidad, etc., es diferente, correspondiendo los mayores grados de alterabilidad a las dolomías arenosas y nodulosas. La mayor susceptibilidad a la alteración de estas dolomías frente a las dolomías homogéneas está controlada, como factor fundamental aunque no exclusivo, por su diferente porometría y accesibilidad del agua al sistema de poros. Los resultados derivados de los ensayos petrofísicos son plenamente contrastables con la observación de los distintos estados de alteración de las dolomías en la Catedral de Toledo.
Investigation on building stones used in the Toledo Cathedral (Central Spain) resulted in the recognition of the sedimentary formations that supplied dolostones during the earlier works in the Cathedral (XIII to XV centuries). Such formations are located in the Cerro de la Rosa, an area close to Toledo where the finding of remains of marine fauna at the beginning of the present century lead to scientific controversy. Main controversy dealt with the chronological attribution of the fossil fauna (Cretaceous, Oligocene, or lower Miocene, after different authors) and subsequent paleogeographical implications for the geology of the Tajo Basin and adjacent areas. This study concludes that the Cerro de la Rosa outcrop is made up of marine faune bearing-carbonate and terrigenous deposits of late Cretaceous age overlain unconformably by early Paleogene continental sediments. This basic stratigraphic framework is relevant as it allows to solve the aforementioned geological controversy. Petrographic and petrophysic testing of the Cerro de la Rosa dolostones leads to the distinction of three main dolostone types (homogeneous, sandy, and nodular dolostones), the three types showing different behaviour in terms of absorption, capilarity, desorption, durability, etc. Higher weatheling rates are determined in both sandy and nodular dolostones, this being controlled by higher porometry and water accesibility to the pore network. Results obtained from petrophysical testing in laboratory fit well with observations on weathering degree of the dolostones in the Toledo Cathedral
Investigation on building stones used in the Toledo Cathedral (Central Spain) resulted in the recognition of the sedimentary formations that supplied dolostones during the earlier works in the Cathedral (XIII to XV centuries). Such formations are located in the Cerro de la Rosa, an area close to Toledo where the finding of remains of marine fauna at the beginning of the present century lead to scientific controversy. Main controversy dealt with the chronological attribution of the fossil fauna (Cretaceous, Oligocene, or lower Miocene, after different authors) and subsequent paleogeographical implications for the geology of the Tajo Basin and adjacent areas. This study concludes that the Cerro de la Rosa outcrop is made up of marine faune bearing-carbonate and terrigenous deposits of late Cretaceous age overlain unconformably by early Paleogene continental sediments. This basic stratigraphic framework is relevant as it allows to solve the aforementioned geological controversy. Petrographic and petrophysic testing of the Cerro de la Rosa dolostones leads to the distinction of three main dolostone types (homogeneous, sandy, and nodular dolostones), the three types showing different behaviour in terms of absorption, capilarity, desorption, durability, etc. Higher weatheling rates are determined in both sandy and nodular dolostones, this being controlled by higher porometry and water accesibility to the pore network. Results obtained from petrophysical testing in laboratory fit well with observations on weathering degree of the dolostones in the Toledo Cathedral