Composición isotópica (δ13C, δ18O y δD) de perfiles mixtos de calcretas-silcretas: significado paleoambiental (Mioceno, área de Torrijos, Cuenca de Madrid)
In this paper the isotopic stable isotopes of three calcrete-silcrete profiles are studied. The profiles correspond to the top of the Lower Miocene Unit of the SE Madrid basin and developed on fine-grained detrital deposits formed in distal alluvial fan systems. δ13CPDB and δ18OPDB analyses were car...
| Autores: | , , |
|---|---|
| Tipo de recurso: | artículo |
| Fecha de publicación: | 2014 |
| País: | España |
| Institución: | Universidad de Huelva (UHU) |
| Repositorio: | Arias Montano. Repositorio Institucional de la Universidad de Huelva |
| Idioma: | español |
| OAI Identifier: | oai:ariasmontano.uhu.es:10272/10651 |
| Acceso en línea: | http://hdl.handle.net/10272/10651 |
| Access Level: | acceso abierto |
| Palabra clave: | Stable isotopes Calcretes Silicification Rizoliths Groundwater Isótopos estables Calcretas Silicificación Rizolitos Freático |
| Sumario: | In this paper the isotopic stable isotopes of three calcrete-silcrete profiles are studied. The profiles correspond to the top of the Lower Miocene Unit of the SE Madrid basin and developed on fine-grained detrital deposits formed in distal alluvial fan systems. δ13CPDB and δ18OPDB analyses were carried on the carbonate samples (calcite), whereas δ18OSMOW and δDSMOW, were analyzed in the silica minerals (quartz, opal and moganite). The results indicate that the calcrete-silcrete profiles formed by the influence of meteoric percolating waters. The values obtained in the calcretes indicate meteoric waters, slightly modified, and a great influence of vegetation, especially C3 plants, in the precipitation of soil carbonate. The water responsible for silcrete formation was very similar in the three studied profiles. δ18O and δ D ratios do not fit the global meteoric water line, probably due to evaporation. Most of silicification processes were from groundwaters of δ18OSMOW values between -6 and -8‰. However, the very early silicification processes, localized in roots, were produced in microenvironments with slightly more evaporated waters (between -4 and -6 ‰) due probably to evapotranspiration |
|---|