Forming factors and properties of soils developed over limestone in Galicia

[Abstract] We describe the forming factors, properties, typology and distribution of soils developed over limestone in Galicia. According to the degree of development, three main tipes are distinguished. AR soils in high-erosion localities are decarbonated. AC soils formed by colluvial deposits of limestone material on, hillslopes have high carbonate levels, partly due to the greater solubility of unconsolidated material. ABR soils are found in relatively stable hillslope positions, in flat areas and cracks of rocks. Some are moderately well developed, with Bw horizons that have high carbonate content. Others are highly developed, with thick, totally decarbonated Bt horizons sometimes with low base saturation. The properties of all these soils depend on the degree of decarbonation

Caracterización de suelos con horizonte mólico formado sobre calizas en clima templado húmedo (Galicia, NW España)

[Abstract] Soils with a mollic horizon lying directly over limestone were characterized physicochemically, mineralogically and micromorphologically. The development of these soils involves dissolution of limestone and leaching of the released calcium carbonate under favourable climatic and topographic conditions, the incorporation of insoluble residues (chiefly by inheritance rather than transformation), and the action of efficient humification mechanism. They are classified as Lithic Haprendolls by Soil Taxonomy (1998) and as Rendzic Leptosols by the FAO classification (1998).

Distribution and Origin of Iron Oxides in Soils over Limestone

[Resumen] Se pretende conocer la distribuci6n y el origen de los compuestos de hierro en suelos formados sobre calizas en Galicia. Predominan las formas minerales de hierro, encontrando en la fracción arena magnetita, goethita y/o hematites y excepcionalmente ilmenita, que se consideran heredadas del material de partida. En lámina delgada se observaron goethita y hematites como granos aislados, constituyendo nódulos e integrados en fragmentos de caliza. En la arcilla, trazas de goethita están presentes en casi todos los perfiles; s610 en uno de ellos la hematites es el único 6xido de hierro. La goethita puede haberse formado tanto por neoformaci6n como por microdivisi6n a partir de las fracciones gruesas, siendo este último fen6meno el que ha originado la hematites de la fracci6n arcilla. En dos perfiles la goethita va acompañada de magnetita y se discute la posible existencía y formaci6n de maghemita.[Abstract] Iron distribution in soils formed over limestone of Galicia is studied an the origin of the different iron forms is established. Organic iron is very scarce and mineral iron components dominate. Magnetite, goethite and / or hematite, less cornmonly ilmenite, are found in the sand fraction; they are considered as interited from the parent material. In polished sections goethite an hematite appear as single grains, nodules and il1corporated into limestone fragments. In the clay fraction, traces of goethite are present in aH except one of the profiles where only traces of hematite are indentified. Neoformation and microdivision from coarse fractions can act in the genesis of goethite; only microdivision is considered as the origin of hematite. Magnetite accompanies goethite in two profiles; the possible presence of maghemite and its origin is also discusse

Alteración de los monumentos graníticos en la provincia de La Coruña: datos preliminares

[Resumen] Se estudian una serie de edificios monumentales de la provincia de la Coruña construidos con materiales graniticos distribuidos por todo su territorio, tanto en el interior como en la zona costera. El objeto del trabajo es el de evaluar el estado de alteración de dichos edificios y conocer las principales causas y mecanismos que la producen Se ha encontrado que presentan diferentes formas de alteración según la parte del edificio que se considere y el tamaño de grano del material.[Résumé] On á etudié une serie de batiments monumentales á la province de la Coruña construits avec des materiels granitiques distribués dans tout le territoire tant al'interieur cornme á la zone de la cote. L'objet du travail c'est l'evaluation de l'etat d'altération de ces batiments et connaitre les principaux motifs et mechanismes qui la produissent. On á trouvé qu' ils pr~sent differents formes d'alteration selon la part du batiment qu' on considere et la grandeur des grains du materiel

Composición mineralógica de los suelos del área de Mera (Las Mariñas): relación con los factores edafonegéticos

[Resumen] Se estudia la composición mineralógica de la fracción arena y arcilla de los distintos tipos de suelos existentes en el área de Mera (Las Mariñas). Durante el Terciario Y Cuaternario el marco geológico, constituido por esquistos de la Formación de Ordenes-Bergondo, ha experimentado varios procesos de edafogénesis y morfogénesis que han onigtnado una serie de depósitos,saprolitas y suelos de diferente composición mineralogica, si bien se observa una clara tendencia a la formación de una facies constituida por caolinita, cuarzo y oxi-hidróxidos de Fe. - El estudio mineralógico permite establecer las secuencias de evolución de los materiales originales en las condiciones existentes[Abstract] A study of the minera1ogica1 composition of the sand and c1ay fractions of soils in the litle area shows that during the tertiary and quaternary periods the Ordenes-Bergondo Schists of the surrounding basin have undergone processes producing a series of sediments, sapro1ites and soils of varied composition in which a facies of cao1inite, quartz and oxy-hydroxides of iron predominates. The evo1utionary sequence of the parent material under the various existing conditions has been determine

Gas chromatography applied to cultural heritage. Analysis of dark patinas on granite surfaces

The formation of dark patinas has been mainly related with deposition of gases and particles, and sulphation mechanisms particularly in calcareous rocks. However, in granitic monuments located in Galicia (northwest of Spain), especially in rural areas, this origin is unlikely since granite is a very poor calcium-containing rock and the atmospheric pollution in this area is negligible. A biological origin seems to be most probable. In order to know the importance of biological and atmospheric factors in the formation of dark patinas on granitic monuments, a number of analyses using several techniques are needed. The characterization of fatty acids in patinas by gas chromatography has established clear differences among samples. Thus, all of the samples having a biological origin displayed a similar fatty acid pattern, with unsaturated fatty acids predominating, especially oleic and linoleic acids; these were followed in abundance by the branched fatty acid 18:00 anteiso, and palmitic acid. Different patterns of fatty acid allowed establishment of an anthropogenic origin of the some of the patinas analysed. © 2007 Elsevier B.V. All rights reserved.Peer Reviewe

Mineralogical Transformation and Neoformation in Granite Caused by the Lichens Tephromela otra and Ochrolechia parella

9 pages, figures, and tables statistics.Tephromela atra and Ochrolechia parella are among the most abundant lichens colonizing granitic monuments in the region of Galicia (northwest Spain). In this work, their interaction with a two-mica granite used in the construction of the Toxosoutos Monastery (Noia, Galicia) was studies, using optical microscopy, scanning electron microscopy (with back-scattered-electron and energy-dispersive X-ray detection), X-ray diffractometry and atomic absorption spectroscopy to evaluate their physical, mineralogical and chemical effects.Peer reviewe

Induction of biofilms on quartz surfaces as a means of reducingthe visual impact of quartz quarries

In the present study the induction of biofilms on the open rock faces of quartz quarries is reported as a feasible method of correcting the visual impact generated by the industry. Experiments were carried out to colonize quartz samples with microorganisms isolated directly from aged quarry faces. The results demonstrated the viability of inducing colonisation on quartz, which is not the most favourable material for such treatment. Furthermore, biofilm development caused a significant change in the colour of the surface of the quartz samples to greenish- or reddish yellow, which may be quantified by a colorimeter for solids. The notable change in the colour is sufficient to attenuate the bright white aspect of the quartz faces and therefore to correct the visual impact generated.Peer Reviewe

Gypsum-induced decay in granite monuments in Northwestern Spain

One of the most common forms of decay in granite monuments is the detachment of the superficial layer of the stone (plaques, plaquettes and scales). Previous studies of granite monuments in the northwest Iberian Peninsula revealed a direct relation between this type of weathering and the presence of calcium sulphate, and a mechanism whereby the salt causes this type of decay was suggested. In the present study, various hypotheses as regards the origin of the gypsum found in granite monuments are proposed. The study involved analysis of the contents of ions soluble in water, the results of X-ray diffraction analyses and the ratios of CaO/SO<sub>3</sub> in samples of stone, mortar and deposits collected from different monuments. It was concluded that in most cases the gypsum originated from old paintworks or/and from the joint mortars, although inputs from other sources cannot be discounted, as discussed<br><br>Una de las formas de deterioro más frecuente en los monumentos graníticos es la separación de la capa superficial de la piedra (placas, plaquetas y escamas). En trabajos anteriores centrados en monumentos del noroeste de la Península Ibérica, se constató la relación directa entre esta forma de alteración y la presencia de sulfato de calcio y se propuso el mecanismo a través del cual esta sal provoca este tipo de deterioro. En este trabajo se plantean varias hipótesis acerca del origen del yeso encontrado en monumentos graníticos. Para ello se comparan los contenidos de iones solubilizados en agua, los resultados de difracción de rayos X y las relaciones OCa/SO<sub>3</sub> de muestras de piedra, morteros y depósitos recogidas en diferentes monumentos. Se llega a la conclusión de que en la mayor parte de los casos el yeso procede de antiguas pinturas o de revestimientos superficiales y de los morteros de juntas entre sillares, pero no se puede descartar la contribución de otros aportes, los cuales se discuten también en este artículo