TAZ-TFG-2015-2027


Depósitos silexíticos en el terciario continental de la Cuenca de Calatayud: Caracterización y génesis

Laita Florián, Elisa
Mandado Collado, Juan M. A. (dir.)

Universidad de Zaragoza, CIEN, 2015
Ciencias de la Tierra department, Petrología y Geoquímica area

Graduado en Geología

Abstract: The tertiary Calatayud Basin is a NW-SE elongated depression, extending from Calatayud (Zaragoza) to Montalbán (Teruel) and whose dimensions are approximately 130 km long and 20 km wide. This basin consists of two distinct sub-basins separated by the Daroca High (Calatayud Basin in the northern sector and Montalbán Basin in the sourthern sector). These Basins present a quite similar sedimentary evolution of the Neogene evaporitic and carbonatic lacustrine systems, that generally ocuppy central locations in both basins. Three main sedimentary units (Lower, Intermediate and Upper units) divided by two main sedimentary breaks are traditionally described in the Calatayud Basin. The lower and the Intermediate units have evaporitic sedimentation, whilst the Upper Unit is typically freshwater fluvio-lacustrine sedimentation. This work focuses on the study of carbonatic materials placed in the Cristo de Ribota hermitage area, which is localized in the Intermediate Unit of Calatayud Basin, to the Northern of Sierra de Armantes. The interest of this area lies in the presence of silexitic levels, whose thickness can be metric, exceptional in the geologic record and that it raises interesting troubles at the time of establishing a hypothesis on the possible origin of the silica that generates these sílex deposits, as well as in the establishment of a genetic model. The sílex levels in the Cristo de Ribota series appear mainly in carbonate rocks. Petrographic studies of the samples taken in this area show a replacement of silica by carbonate, as well as a silica cementation in karts cavities generated by epidiagenetic karts processes. These cavities acted as conduits for fluids saturated in silica which resulted in silex deposits. The fluids should necessarily have an episodic character and the fact that karstic cavities can be filled with silica or carbonate is an evidence of it. For the silica precipitation, not only the low temperature and a less than 9 pH are necessary, but also there must exist a lot of silica-supersatured water, as well as a high permeability. The source of silica deposits in this area is probably diagenetic, but also it would be necessary to consider a thermal origin corresponding to the contribution of silica by hydrothermal fluids.

Tipo de Trabajo Académico: Trabajo Fin de Grado
Notas: Depositada en Secretaría copia en papel

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