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X Congreso Geológico de España, 5-7 Julio 2021, Vitoria - Gasteiz, El análisis de la geometría y cinemática de estructuras oblicuas es necesario para entender su origen y evolución. En este trabajo el estudio de la fábrica magnética se utiliza como una herramienta para determinar la historia deformacional de los pliegues oblicuos situados en el autóctono deformado del sector nororiental de la cuenca de antepaís del Ebro. Un total de 149 estaciones han sido analizadas a partir del análisis de la fábrica magnética (anisotropía de la susceptibilidad magnética) con este objetivo. El muestreo se realizó en materiales detríticos sinorogénicos del Eoceno Superior-Oligoceno del sector de Artesa de Segre-Cardona. A pesar de la dirección de acortamiento regional aproximada N-S, oblicua con respecto a la orientación N045E a N135E de los pliegues estudiados, las direcciones obtenidas de la lineación magnética en la mayoría de los casos se encuentran contenidas en el plano de estratificación y paralelas a los ejes de los pliegues oblicuos. El análisis paleomagnético realizado de forma paralela a este estudio muestra la existencia de rotaciones anti-horarias de estos pliegues relacionadas con el emplazamiento del saliente de cabalgamientos del Pirineo Central (Peigney et al., 2021), lo que sugiere que los elipsoides magnéticos obtenidos han actuado como marcadores pasivos de la deformación registrando información relacionada con el acortamiento paralelo a las capas inicial (layer parallel shortening) y/o su plegamiento posterior.

Màster de Meteorologia, Facultat de Física, Universitat de Barcelona, Curs: 2020-2021, Tutor: Joan Bech, The objective of this work is to study rainfall characteristics (frequency, amount and type) in a semi-arid region in the Eastern Ebro basin (Iberian Peninsula). The region is included approximately in a 20 km per 30 km rectangle and is divided in two different areas, one irrigated with an artificial channel, and another one non-irrigated. The two areas may present a big difference of surface temperature in a short distance, particularly during midday hours of summer months due to high evapotranspiration contrasts. The study focusses in finding possible differences in rainfall characteristics between two areas. The methodology used is based on the analysis of radar reflectivity data, which is processed to determine the rainfall type, classified in convective and non-convective, a part of rain occurrence and amount. The work examined June, July and August data from years 2014 to 2020 analysing daily, monthly and total rain events distributions in both areas. The results show a big variability of the rainfall in the region depending on the year and as expected, an increase in convective rain in both areas during the afternoon. Although there is not a significant difference in the rainfall type nor in the convective rainfall rate between areas, there is a difference in the convective rain distribution along each area, being the rain in the irrigated part less homogenous than the non-irrigated part. This study has been performed in the framework of the Analysis of Precipitation Processes in the Eastern Ebro Subbasin project (WISE-PreP, RTI2018-098693-B-C32/AEI).

The term “gypsiferous silts” has been used since the 1960s by many authors, but it has relied on unclear, ambiguous criteria that attributed aeolian, colluvial or alluvial origins to these materials. The aim of this paper is to clarify the use of the term “gypsiferous silts” applied to silt-sized, gypsum-bearing sediments on surface formations in the Ebro Basin, using published and unpublished information. We distinguished three types of materials with very different characteristics that had all been attributed to the general term “gypsiferous silts” in previously published work: I) gypsiferous silts sensu stricto, ii) loess and iii) flour-like gypsum. The recommendations of our study are that the first two terms should be applied to gypsumcontaining sediments located in varied topographic positions with calcium carbonate contents up to 40-50% and coarse silty to fine sandy textures. Loess normally appears as thick outcrops (up to 12m) on slopes leeward from the main wind direction, with a limited pedogenesis consisting of a partial carbonate mobilisation and gypsum contents between 0 and 30%. Loess is the only category with an aeolian origin. The materials in the category “gypsiferous silts” sensu stricto are mainly colluvial-alluvial. The third term (flour-like gypsum) should be used to refer to materials on surface formations consisting of almost 100% silt- to fine sand size lenticular gypsum. These materials derive from on-site weathering of gyprock or by precipitation from calcium- and sulphate-saturated groundwater and surficial waters and show a variable spatial distribution: Along footslopes, outcropping as metric surface formations, interstratified between limestone layers or as generalized karstified subsurface accumulations. The proposed classification, based on morphological and physico-chemical characteristics, establishes a necessary distinction among the three types of materials, since they differ in their properties and geotechnical behavior relevant for soil management and land use. Using the proposed classification will allow their distinct characteristics can be taken into account when performing geological or soil surveys in this and similar arid regions. This work has been done in the frame of the Project LOESSIBERUS, RTI2018-094927-B-I00, Ministerio de Ciencia, Innovación y Universidades, Spain. We thank Dr. G. Benito, C. Arenas and an anonymous referee for their constructive comments when revising the manuscript, and Dr. Michele Francis (U. Stellenbosch) for her careful language revision.

Dating the sedimentary infill of the northern margin of the Ebro foreland basin informs about the orogen-basin evolution. A magnetostratigraphic section of ~5 km-thick combines new magnetostratigraphic results from the syntectonic alluvial Uncastillo Fm (Upper Oligocene-Lower Miocene, 1 km-thick, the Fuencalderas section) with previous (3.3 km-thick) and new (0.7 km-thick) magnetostratigraphic data from the underlying fluvial Campodarbe Fm (Luesia and San Marzal sections, Eocene-Oligocene). This composite section allows dating the entire basin infill in this sector, therefore bracketing the timing of the deformation in the southern margin of the Pyrenees after considering previous kinematic studies. Deformation recorded by the continental deposits spans from syn-Gavarnie nappe activity (Broto and Fiscal basement thrust sheets) from 31.3 to 24.55 Ma, Rupelian-Chattian (Oligocene) to the syn-Guarga thrust activity, from 24.55 to 21.2 Ma Chattian-Aquitanian (Oligocene-Miocene). The Accumulation rates vary from ca. 22 to ca. 39 cm/kyr between the genetic stratigraphic units in the Uncastillo Fm through the section. These rates are close to those of the underlying deposits of the Campodarbe Fm (average of ca. 36 cm/kyr). Deformation for the latest Pyrenean front (syn-Guarga thrust) is younger than previously assigned in ~5.4. ~1.5 and ~1.1 Myr of the beginning of the Punta Común thrust sheet (from 29.4 Ma to 24 Ma), Lower Riglos thrust sheet system (from 24 to 22.5 Ma) and the Upper Riglos thrust system (22.5 to 21.4 Ma) respectively. Other significant changes in accumulation rate and its derivative also indicate variations in the tectonic activity ca. 33 and 28 Ma. © 2019 Elsevier B.V., Financial support was provided by the Spanish Ministry with the SEROS project, reference: CGL2014-55900-P/BTE and the project DR3AM-CGL2014-54118-C2-2-R. Thanks to the Paleomagnetic Laboratory CCiTUB-ICTJA CSIC, the Geomodels Research Institute, the Grup de Geodinàmica i Anàlisi de Conques - 2017SGR00596 and Geotransfer Group at the University of Zaragoza.

Adequate characterization of depositional architecture is of great importance when studying fluvial outcrops as reservoir analogs. The complex three-dimensional (3D) distribution and lateral and vertical relationships of sandstone bodies require a high degree of stratigraphic control in order to make a proper assessment of the distribution and connectivity of the reservoir facies. This assessment demands the use of reliable correlation datums. Unfortunately, clear marker beds (e.g., ash layers, coal beds, and paleosols) are not always available in fluvial outcrops, and when present, they are often covered by vegetation or debris that prevents their tracking over long distances. A new method to achieve highly accurate and semiautomatic correlations within fluvial digital outcrop models (DOMs) is presented in response to the need for further correlation procedures, especially in the absence of suitable datums. The method is based on the hypothesis that the average depositional paleosurface of a sedimentary system can be represented by a plane at outcrop scale. If this assumption is valid, this plane can be used as a virtual datum to identify along the DOM the sediments that were deposited simultaneously. The method was tested and applied successfully within two kilometer-scale outcrops of the Huesca fluvial fan (Early Miocene, northern Spain), where the virtual datum provided accurate correlations regardless of stratigraphic or topographical complexities. Moreover, all the sedimentary successions of the outcrops could be automatically subdivided into the desired stratigraphic intervals by only moving the virtual datum vertically. These intervals can be subsequently isolated to facilitate the detection of subtle variations and trends of their fluvial properties. Consequently, a virtual datum is the equivalent of having a marker bed crossing the stratigraphic succession of an outcrop at any desired position. The advantages provided by a virtual datum prove to be especially useful in large and topographically complex outcrops that previously could not have been studied with such a high degree of 3D stratigraphic control.

Chert from the limestones and marly limestones of Castelltallat Formation (Ebro Basin) was widely used throughout prehistoric times in north-eastern Iberia to produce stone tools due to its properties and accessibility. A rough estimate indicates that this rock—either as raw material or as lithic products—was distributed mainly to the north of the outcrops, over an area of 6000–8000 km2. However, other rocks in the area have similar characteristics which can lead to confusion in the interpretation of its prehistoric use and distribution. In order to establish useful archaeometric criteria for differentiating this chert from other similar, the Castelltallat chert is characterised in petrographic, mineralogical and geochemical terms. The chert nodules are found to be homogenous at the macroscopic and microscopic level, with a significant presence of bioclasts, thus indicating they might be formed in a freshwater lake environment by the early diagenetic replacement of carbonates in shallow waters. The mineralogical composition is homogeneously uniform and of a flint type, characterised by an almost exclusive predominance of quartz, without any opaline phases, and a variable proportion of moganite. The iron oxide content is very low, whereas its chemical composition is unusually high in uranium which correlates positively with carbonate content and negatively with silica. Archaeometrical parameters are provided to reach a proper identification of tools knapped with this chert. This way, chert from Castelltallat Formation turns out to be a valuable lithological marker to evaluate the range of mobility of the human groups who lived in the north-eastern Iberia and their contacts with neighbouring areas., The fieldwork to obtain rock samples and the analysis of the samples was cofunded by the Direcció General del Patrimoni Cultural de la Generalitat de Catalunya and IMF-CSIC, within the framework of an interinstitutional collaboration agreement for the development of the Catalan Lithotheque of siliceous rocks (LITOcat project). Specific studies on the petrological characterisation of Castelltallat chert and its prehistoric use were carried out within the research project ‘Aprofitament prehistòric i històric del sílex a Catalunya: contextos extractius i de primera transformació’, funded by the Department of Culture of the Government of Catalonia (ref. núm. 2014/100778). The significance of human use and scope of distribution of Castelltallat chert are being approached within the project ‘Productions, technical variability and technological innovation in the Neolithic’, funded by the Spanish Ministry of Economy and Competitiveness (Grant HAR2016–76534-C2–2-R).

Southern Pyrenean frontal thrusts are usually blind or partially covered by syn- and post-tectonic sediments of the Ebro Foreland hampering their interpretation. We have investigated the geometry and evolution of the Súria Anticline, a frontal structure of the Southern Pyrenees, which is characterized by the presence of multiple buried and blind thrusts displaying a complex triangle zone and several fishtail structures at depth. To characterize the geometry and structural evolution, a combination of surface geology, subsurface data interpretation, and analog modeling have been integrated into a unique 3D geologic model. The surface geology of this area depicts a rather simple structure, characterized by a north-directed backthrust and a gentle anticline, both striking west–southwest/east–northeast. In contrast, geophysical data indicate that the subsurface structure is more complex, exhibiting several northward- and southward-directed thrusts and folds detaching on the Pyrenean foreland Eocene evaporites. Integration of surface (geologic maps and dip measurements) and subsurface data (seismic and wells) allowed us to reconstruct the 3D structure of this area. To produce a more robust kinematic model, we used an experimental approach to investigate the evolution of frontal structures in folds and thrust belts on evaporitic detachments. Different viscous layer configurations were tested in a series of sandbox models comparing them with the evolution of the Súria Anticline. Taking into account the deformation and that seismic quality is in general poor, the experimental results allow us to better characterize the structures developed in this area. Our structural evolution is characterized by an early stage of salt inflation and fold nucleation. With increasing shortening, the structure evolved to a detachment anticline eventually developing a northward-directed thrust that broke through the northern anticline limb. The present-day geometry developed in a later stage of fold reactivation, when a new regional fold formed, and tightened the preexisting structure.

En cinturones de pliegues y cabalgamientos con niveles evaporíticos es típico el desarrollo de pliegues de adaptación de falla y de despegue. La geometría de estas estructuras, su cinemática, y sus propiedades mecánicas han sido ampliamente analizadas. Sin embargo, gran parte de la literatura existente se ha centrado en el estudio de los niveles evaporíticos pre-cinemáticos sin discutir el rol de los niveles evaporíticos depositados durante la deformación contractiva cuando, en realidad, son comunes en cuencas de antepaís deformadas (p.e., Cuenca de Tarim o Zagros, o Cuenca del Ebro entre otras). Este trabajo se centra en la caracterización de la estructura de una zona del frente surpirenaico central mediante la realización de una cartografía geológica de detalle apoyada en un corte geológico compensado. El objetivo es mostrar el papel que han tenido los niveles evaporíticos sin-orogénicos (Paleogeno) en la geometría y evolución cinemática del frente surpirenaico central. Los resultados muestran que la terminación meridional de la sal sin-orogénica de la Fm. Cardona controla la posición del pliegue de despegue de Sanaüja. Y en la terminación meridional de los yesos sinorogénicos de la Fm. Barbastro se forma una estructura tipo cola de pez que en superficie se corresponde con el pliegue de adaptación de falla de La Sentiu - Almenara.

La Plana de Vic, situada hacia el sector NE de la Cuenca del Ebro, se caracteriza por un espeso apilamiento de materiales marinos que fueron acumulados principalmente durante el Paleógeno. Sobre una discordancia desarrollada sobre el basamento paleozoico se acumularon materiales aluviales distales de granulometría fina (Taneciense) que quedaron recubiertos por una delgada cuña marina (Ilerdiense). Encima existen materiales aluviales distales de granulometría fina que pasan gradualmente a otros de granulometría gruesa, que en su parte superior muestran intercalaciones de areniscas y carbonatos con Nummulites y Assilina (Luteciense). Posteriormente, se depositaron lutitas de offshore que soportaron la progradación de materiales arenosos costeros. En la parte central de la cuenca siguió la acumulación de lutitas (Bartoniense) que a su vez fueron afectadas por progradaciones deltaicas en los sectores meridionales y septentrionales. A techo de algunos cuerpos deltaicos se depositaron litosomas arrecifales carbonatados. Sobre una discontinuidad sedimentaria aparece una acumulación compleja de lutitas, areniscas, evaporitas y carbonatos donde se hallan los nuevos yacimientos de peces fósiles (Priaboniense). Entre los especímenes se han identificado algunos Clupeidos, Percofórmidos y Synodontidos que representan los últimos episodios de la sedimentación marina en la zona durante el Eoceno The Plana de Vic is located towards the NE of the Ebro Basin and is mainly characterized by a thick pile of marine sediments that accumulated along the Palaeogene. Overlying a Palaeozoic basement and a marked unconformity are fine-grained non-marine materials (Thanetian), which are covered by the accumulation of a thin marine wedge (Ilerdian). These marine materials were subsequently overlain by fine- and coarse-grained alluvial deposits. Towards the upper part of these alluvial deposits are sandstones and limestones with Nummulites and Assilina. Thereafter, lutitic materials deposited offshore were covered by the prograding coastal sandy materials. In the central part of the basin the accumulation of offshore lutites continued (Bartonian). These lutites were affected by the southwards and northwards deltaic progradations. Limestonedominated reefs were deposited over the deltaic bodies. On top of the sedimentary unconformity is a complex accumulation of lutites, sandstones, evaporites and limestones (Terminal complex) containing the remains of the fossilized fish (Priabonian). Some specimens of Clupeids, Percoformids and Synodonts represent the last episodes of the Eocene marine sedimentation in the study area

The results of anisotropy of magnetic susceptibility analyses of 19 sites carried out on magnetostrigraphically-dated, Lower to Middle Miocene (20.4 to 13.7 Ma) “non-deformed” mudstones from the central part of the Ebro basin reveal the presence of a subtle tectonic overprint lasting at least until the Langhian (Middle Miocene) in the southern Pyrenean foreland. Magnetic ellipsoids show a sedimentary fabric in 42% of sites and a weak and well-defined magnetic lineation in 47% and 11% of sites. The magnetic lineation is roughly oriented around the east–west direction, compatible with a very weak deformation occurring there and related to the north–south compression linked to the convergence between Europe, Iberia and Africa during the Early–Middle Miocene. A slight variation of the magnetic parameters Km, Pj, and T exists through time, probably due to changes in the sedimentary conditions in the basin., Funding for this work came from project CGL2013-42670-P (Ministry of Economy and Competitiveness, Spain) and a JAE-Doc Postdoctoral (CSIC, Spain) contract for the first author.

Las nuevas técnicas de recolección de datos digitales surgidas en los últimos años han dado lugar a avances significativos en el campo de la caracterización de afloramientos. Esta evolución se basa en la premisa de que cuanto mayor sea la cantidad, la calidad (exactitud), y la velocidad de recolección de los datos, mejores serán las interpretaciones y modelos que se deriven de ellos. Una de las técnicas más recientemente incorporadas en el estudio de afloramientos geológicos es el escaneo láser terrestre (TLS), el cual se basa en la tecnología lidar (desarrollada en la década de 1960). El objetivo principal de esta tesis es aprovechar el potencial del TLS para desarrollar nuevas herramientas y metodologías que permitan resolver la principal limitación a la que se enfrentan los geólogos cuando trabajan en afloramientos fluviales: adquirir el control estratigráfico necesario para detectar, comprender y caracterizar el alto grado de heterogeneidad en el espacio y el tiempo que muestran las sucesiones fluviales. Con este propósito se han adquirido datos con TLS en 8 afloramientos del Abanico Fluvial de Huesca (Mioceno inferior, norte de España). Se han utilizado softwares comerciales para procesar las nubes de puntos adquiridas y así obtener Afloramientos Virtuales (VO’s), pero la mayor parte de los logros obtenidos de su estudio fueron posibles gracias softwares desarrollados en la propia facultad. Por otro lado, también se han medido varias columnas estratigráficas detalladas y se recogieron muestras litológicas de diferentes tipos de cuerpos areniscosos. En base a estos datos y a las observaciones realizadas sobre el terreno los resultados más relevantes obtenidos son los siguientes: * Una caracterización detallada de las facies fluviales, la cual incluye el estudio de las propiedades petrológicas y petrofísicas de los cuerpos areniscosos. * Un método simple que se sirve del VO para corregir las alturas y espesores de los cuerpos sedimentarios medidos en las columnas estratigráficas. Los principales factores que pueden haber influido en las mediciones realizadas con Vara de Jacob han sido estudiados y discutidos. * Se ha establecido un nuevo método que permite realizar correlaciones semiautomáticas y altamente precisas en los VO’s de afloramientos fluviales, el cual se basa en la hipótesis de que el paleosuperficie deposicional del sistema sedimentario puede ser representada por un plano a escala de afloramiento. Si esta suposición se cumple en el afloramiento, este plano puede ser utilizado como un datum virtual para identificar a lo largo del VO los sedimentos que fueron depositaron simultáneamente. El método ha sido probado y aplicado con éxito en cuatro afloramientos de escala kilométrica del Abanico Fluvial de Huesca, en los cuales los datums virtuales han proporcionado correlaciones precisas independientemente de las complejidades estratigráficas o topográficas de los mismos. Además, únicamente con mover el datum virtual se puede subdividir toda la sucesión sedimentaria de los afloramientos en los intervalos estratigráficos deseados, los cuales pueden ser aislados del resto para facilitar su estudio en detalle. * Los datums virtuales también se han utilizado como base para establecer un nuevo procedimiento que permite inferir cuales son las posiciones estratigráficas relativas dentro de toda la secuencia fluvial de afloramientos que distan decenas de kilómetros. * Se ha realizado una modelización estocástica de facies basada en objetos que se sirve de los datos obtenidos al aplicar un nuevo método para extraer de una manera semiautomática las superficies del VO que pertenecen a paleocanales. Los flujos de trabajo de modelización de análogos habituales utilizan los datos de columnas estratigráficas (en forma de pseudopozos) para condicionar las simulaciones, pero con el método presentado aquí toda la superficie del afloramiento es considerada para este propósito, aumentando significativamente de ajuste del modelo a la realidad. Gracias a la utilización de la tecnología lidar en afloramientos del Abanico Fluvial de Huesca se han conseguido establecer diferentes métodos de trabajo que han demostrado ser útiles de cara a facilitar y mejorar la construcción de modelos de análogos de reservorio. Además, se considera que su aplicación puede sin duda contribuir a mejorar nuestra comprensión de los factores y mecanismos que influyeron en la evolución de los sistemas sedimentarios fluviales antiguos., Terrestrial laser scanning (TLS) is based on lidar technology, which although developed in the early 1960s, has only recently been incorporated into the study of geological outcrops. The main aim of this thesis is to take advantage of the potential of the TLS to provide new tools and methodologies focused on solving the main limitation found by the geologists when working in fluvial outcrops: acquire the degree of stratigraphic control required to detect, understand and characterize the high degree of spatial and temporal heterogeneity of fluvial successions. TLS data from 8 outcrops of the Huesca Fluvial Fan (Early Miocene, northern Spain) were acquired to this purpose. In addition, several detailed stratigraphic columns were measured and lithological samples from different types of sandstone bodies were collected. Based on this, the most relevant results obtained are as follows: * A comprehensive characterization of the fluvial facies that includes the petrological and petrophysical properties of the sandstone bodies. * A simple method using the VO to correct the heights and thicknesses of the sedimentary bodies measured in the stratigraphic columns. The main factors that may have influenced the measurements made with the Jacob’s staff have been studied and discussed. * A new method leading to obtain a virtual datum is presented in response to the need for further correlation procedures, especially in the absence of suitable datums. This virtual datum enables to achieve highly accurate and semiautomatic correlations within fluvial VO’s. Moreover, all the sedimentary successions of the outcrops can be automatically subdivided into the desired stratigraphic intervals (which can be later isolated) by only moving the virtual datum vertically. * The virtual datums were also used to establish a new procedure that leads to infer the relative stratigraphic positions of distant outcrops (more than 10 Km apart) inside the entire fluvial sequence. * A facies modelling has been performed using a new method to extract in a semiautomatic way the surfaces of the outcrop that belong to paleochannel exposures.