Estratigrafía y tectónica del Terciario en el sector Nigüella-Mesones de Isuela (Zaragoza)

Santos Bueno, Nerea
Arenas Abad, Concepción (dir.) ; Gil Imaz, Andrés (dir.)

Universidad de Zaragoza, CIEN, 2015
Ciencias de la Tierra department, Estratigrafía area

Graduado en Geología

Abstract: This work is focussed on the Tertiary materials situated in the Nigüella-Mesones de Isuela sector (Zaragoza province, Spain). These materials unconformably overlie different Mesozoic units and are considered Miocene in age (Ramírez del Pozo et al., 1978). The main tectonic structure affecting the Tertiary is a NW-SE syncline, which extends towards NW outside the study area. We have studied their SE extreme. The main objectives of the study were the knowledge of the general geological history of the Nigüella-Mesones de Isuela sector, focussed on the Tertiary, including the interpretation of their sedimentary environment. To achieve these different objectives we made the geological cartography of the zone (1:10.000) and measured three stratigraphic sections (1:100) through the Tertiary. To interpret the structure, we have made three detailed geological cross sections. There are different small faults with an orientation N-S, E-W and WNW-ESE. However, the main macro-scale tectonic structures are 1) a normal-reverse fault (Nigüella Fault), which, to the North, has a sinestral component, and 2) a Tertiary syncline, both structures with a mean orientation NNW-SSE. The Nigüella Fault affects the Palaeozoic, Mesozoic and Tertiary materials. Tertiary materials were affected by the fault while they were deposited, causing their synsedimentary folding and resulting in the formation of the syncline. Four main Tertiary units were mapped based on lithological and textural criteria; the two intermediate units only crop out in the southern half of the syncline. The total thickness ranges from 112 m in the southern part, to 74 m in the northern part. However, in the central part the thickness is 48 m. Correlation and facies analysis of the measured sections allowed the interpretation and evolution of the sedimentary environment. The main facies associations (FA) are: A) alluvial FA: Fm-->[Gm1, Gm1b]‹—›(Gh); \[Gm1, Gm1a]-->Fm-->(Cm);, B) alluvial-fluvial FA: \,Gm2-->Fm; C) carbonate fluvio-lacustrine FA: [Cbt‹—›Cbtv]-->(Ce)-->[M, (Fm)]-->Cm; [Cbt‹—›Cbtv]<-->[M, (Fm)]-->Cm; and D) carbonate lacustrine FA: M-->Cm. The basin fill in this sector records three main sedimentary stages, with a clear expansion of lacustrine conditions through time: dominant fluvial-alluvial conditions, followed by dominant fluvial-lacustrine conditions and then dominant lacustrine conditions. The nature of the coarse alluvial-fluvial facies and the areal distribution of the lithofacies suggest a principal sediment source (mostly from carbonate Mesozoic drainage areas) from the East and North, with local coarse inputs from the West. However, further studies on a broader area would allow a better approach to this hypothesis. Tertiary compressive tectonics controlled both the sedimentation and the folding of all the sedimentary units, as it is evidenced by the thickness variations of the sedimentary units through the main cartographic-scale syncline. The main NW-SE trending cartographic fault represents an ancient NE dipping lower Mesozoic normal fault responsible for a hectometric-scale vertical slip. Tertiary compression, that controlled the source areas during sedimentation and location of a depocenter in the SW of the study area, gave rise to the buttressing of all the Tertiary record against the fault.

Tipo de Trabajo Académico: Trabajo Fin de Grado

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