Estudio de estructuras gravitacionales asociadas a la karstificación de evaporitas mediante la técnica del trenching

Las formaciones mio-pliocenas en el flanco NO de Los Mansuetos (sección tipo del Turoliense, Fosa de Teruel) están afectadas por subsidencia como consecuencia de la karstificación de las evaporitas triásicas infrayacentes, presentando un monoclinal de 1.7 km de longitud y una sinforma con 130 m de relieve estructural. La cresta del monoclinal está afectada por una fosa que contrarresta el acortamiento causado por la flexión pasiva en el sinclinal adyacente. La fosa está controlada por una falla maestra sintética y un cortejo de fallas sintéticas y antitéticas secundarias con una patente expresión morfológica. Tras la adquisición e interpretación de perfiles de georadar (GPR), se han excavado tres trincheras en depresiones asociadas a escarpes orientados a contra-pendiente. Según nuestro conocimiento, estas son las primeras trincheras excavadas en fallas recientes generadas por karstificación interestratal de evaporitas. Las relaciones geométricas observadas en dos de las trincheras permiten inferir eventos de desplazamiento (hasta 3) ocurridos en el Holoceno reciente. Algunos de los parámetros estimados para las fallas investigadas son claramente diferentes de los esperables para fallas tectónicas en esta zona de intraplaca: Tasas de desplazamiento vertical elevadas (0.6-1 mm/a), baja recurrencia media de los eventos de rotura (1.2-2 ka) y valores de desplazamiento por evento muy elevados (>65 cm) para roturas superficiales de menos de 200 m de longitud. Estos datos sugieren que el considerar las fallas relacionadas con la disolución profunda de evaporitas como estructuras tipo creep no constituye un criterio fiable para diferenciar entre éstas y las fallas tectónicas activas (sismogénicas)

Cartografía geomorfológica de detalle del tramo del valle del Río Jiloca comprendido entre Villafeliche y Fuentes de Jiloca (Zaragoza)

The villages of Villafeliche, Montón and Fuentes de Jiloca are located in the low sectionof the Jiloca Valley, Calatayud Community, Province of Zaragoza. This area presentsgeomorphological diversity because it is in the union area of Aragonese Branch of the IberianChain with the Neogene Calatayud Basin. This modeling is mainly conditioned by tectonic,fluvial and lithological factors.Geomorpholical analysis is performed by geomorphological mapping and descriptionsof deposits and morphologies. Fort he geomorphological mapping has been done on a detailscale 1:15.000. This project includes a geomorphological mapping of the study area realized ona scale 1:25.000 (Annex II) and a scale 1:70.000 (In this dossier, in 9. Geomorphologicalanalysis) and a characterization of the geomorphological elements according to modelling.As a result of geomorphological mapping and the description of morphologies andmodelling, this proyect includes also an evolutionary geomorphological synthesis. Thegeomorphological evolution of this section of Jiloca Valley is more relevant at the end ofMiocene Period, because the processes that have modelled this area until now started at the endof endorheism of Calatayud Basin.<br /

Hydrogeochemical characterization of an evaporite karst area affected by sinkholes (Ebro Valley, NE Spain)

The main processes controlling the hydrochemistry of an alluvium-covered evaporite karst area with high sinkhole risk (Ebro Valley, NE Spain) are examined by means of multivariate analyses (Principal Component Analysis and Hierarchical Cluster Analysis), ion correlations and geochemical speciation-solubility calculations. The hydrogeochemistry of the studied system seems to be governed by the interaction between the groundwater from the salt-bearing evaporitic karst aquifer and from the overlying Ebro River alluvial aquifer. The observed hydrochemical features in the alluvial-karst aquifer system are mainly determined by the relative contribution of gypsum/anhydrite and halite dissolution, showing a wide spectrum from relatively fresh recharge waters (mainly irrigation waters) to highly evolved groundwater from the evaporitic aquifer. The variability of these contributions is especially evident at sinkhole ponds which, in some cases, seem to be associated with discharge areas of the karst aquifer in the valley bottom alluvium. Calculated saturation indexes suggest that, in contrast to gypsum, the amounts of halite in the sampled portions of evaporitic aquifer are not large enough to attain equilibrium, which is consistent with the predominance of gypsum/anhydrite reported for these materials. Furthermore, the observed Na:Cl and Ca:SO4 correlations and stoichiometries suggest that other possible processes, such as glauberite dissolution or Na/Ca-exchange, generally play a minor role (compared to halite and gypsum dissolution) in this system. Another important process in the system is the dissolution of carbonate minerals (dolomite and, possibly, calcite) fostered by the input of CO2(g), which is probably produced by pedogenic processes. Dolomite dissolution seems to be particularly relevant in the evaporitic materials probably due to dedolomitisation triggered by gypsum/anhydrite dissolution