Foreword (2004)

This is the first issue of Geologica Acta dedicated to the memory of Professor Francesc Calvet, whose life was cut short in January 2002 when he was only 54. Francesc was a man with great human qualities, a distinguished scientist and an inspiring teacher who was held in high esteem by all those who knew him. His academic achievements, talent and friendly personality attracted numerous colleagues and students. Unfailingly courteous and polite, he was passionately committed to social justice and was a staunch defender of freedom of conscience and tolerance.

Réplica a las objeciones presentadas por el Sr. Juan Ullastre a la parte gráfica que ilustra un artículo de geofísica del Berguedá y Solsonés (Pre-Pirineo Catalán)

El comentario que con el título de 'Objeciones a la parte gráfica .que ilustra un artículo de geofísica del Berguedá y Solsonés' realiza J.Ullastre a nuestro artículo 'Aportaciones de la prospección geofísica al estudio del subsuelo del Berguedá y Solsonés' publicado en el volumen 27 de esta revista dedicado en homenaje al Dr Oriol Riba, presenta algunos aspectos formales y otros de fondo que merece la pena puntualizar.

Geoquímica aplicada al medio ambiente

En este trabajo se pretende determinar las distintas acciones que los elementos químicos que definen el 'paisaje', ejercen sobre el medio ambiente. Dichas acciones, denominadas positivas o negativas, bajo la óptica humana, se deben a al comportamiento fisico-químico de los elementos, a su interacción con el medio natural y al uso final que de estos elementos da el hombre. Se presentan así mismo los distintos métodos y técnicas que se aplican en la exploración geoquimica, con el fin de examinar las diferentes opciones que estos nos aportan sobre el objeto ya definido. Como objetivo último, este trabajo pretende definir a la 'Geoquimica aplicada al medio ambiente' como la interacción entre la Prospección geoquímica, la Geoepidemiología y la Geoquimica ambiental. Por todo ello, se presentan cinco ejemplos, en zonas próximas a la Ciudad de Barcelona y en la Isla de Menorca.

Coastal salina evaporites of the Triassic-Liassic boundary in the Iberian Peninsula: the Alacón borehole

The evaporite unit (the Lécera Formation), which was formed at the Triassic¿Liassic boundary in the Aragonian Branch of the Iberian Chain, was studied at the 01 Alacón borehole (Alacón village, Teruel province), where it is mainly constituted by a thick (>e and reflect deeper water settings, whereas in the upper part they correspond to shallower water settings. The evaporite sedimentation mainly occurred in a subsiding coastal basin of the salina or lagoon type. In this setting, the subaqueous precipitation of the carbonate and gypsum lithofacies was followed, in each cycle, by the interstitial growth of anhydrite in exposed conditions. As a whole, the evaporite succession reflects an infilling process. The conversion into anhydrite of the selenitic gypsum -probably also of the rest of depositional gypsum lithofaciesstarted under synsedimentary conditions and followed during shallow to moderate burial diagenesis.

Magmatismo paleozoico en el Macizo del Roc de Frausa (Pirineos Orientales)

En el Macizo del Roc de Frausa se han diferenciado mediante criterios geoquímicos dos tipos diferentes de anfibolitas. El primer tipo lo forman metabasitas de afinidad toleitica y composición próxima a los E-MOIIB. Proceden de magmas poco evolucionados moderadamente bajos en potasio. Forman sills intercalados entre los metasedimentos cambro-ordovícicos y están asociadas a porfiroides gneísicos. Los porfiroides gneisicos representan términos ácidos subaluminicos de carácter explosivo y afinidad calcoalcalina con un contenido medio en potasio. Su relación genética con las metabasitas es poco clara; se interpretan como diferenciados ácidos de estas con una importante mezcla de material cortical. Se sugiere para este magmatismo un ámbito geodinámico continental fini-compresivo en relación con cucncas marginales.

Procesos de alteración de materiales pétreos en edificios de interés histórico

Sin pretender ser un trabajo exhaustivo, se exponen las bases generales y las fases de estudio que se realizan actualmente en los trabajos técnicos de diagnosis sobre el estado de conservación de un monumento, como paso previo a la restauración. Los estudios de diagnosis se centran habitualmente en la acción de la contaminación (como factor extrínseco) y en el estudio de la porosidad de la roca y sus propiedades hídncas (como factores intrínsecos). Además de estos factores existen otros procesos de alteración que tienen su origen en la naturaleza mineralógica y sus caractensticas cristaloquímicas (fábricas cristalinas, fases de cemento); se trata de mecanismos que pueden ser determinantes en alteración y que pueden pasar desapercibidos si no se realiza un estudio petrológico y cristaloquimico en profundidad, especialmente con las nuevas técnicas de microscopía electrónica y de análisis puntual con sonda de electrones.

Modelización Gravimétrica 3D del diapiro de Cardona, Cuenca del Ebro (NE de España)

En este trabajo se presentan los resultados derivados de la interpretacón de 320 estaciones gravimétricas realizadas sobre el diapiro de Cardona con el objetivo de obtener información sobre su geometría tridimensional. Para obtener una distribución tridimensional de la masa salina que explique las anomalías observadas se ha aplicado un método iterativo de ajustes sucesivos basado en un algoritmo de inversión automática. Esta metodología ha mostrado ser muy rápida, fácil de usar y con suficiente poder de resolución para perfilar no sólo la geometría del cuerpo salino, sino también la de estructuras similares. El diapiro salino de Cardona presenta un mínimo gravimétrico relacionado con el anticlinal de Pins-Cardona que se prolonga hacia el SW. El análisis cualitativo de la anomalía residual permite apreciar que el diapiro muestra una cierta vergencia hacia sur con un flanco sureste subvertical y un flanco noroeste con pendientes más suaves.

Isotopic characterization of Jurassic evaporites. Aconcagua-Neuquén Basin, Argentina.

1695-6133

Foreword (2007)

This is the second issue of Geologica Acta dedicated to the memory of Professor Francesc Calvet, who passed away in January 2002. Francesc was a man with great human qualities, a distinguished scientist and an inspiring teacher who was held in high esteem by all those who knew him. The first volume contained six papers on specific areas of research in which Francesc was engaged, and a biography (Geologica Acta, volume 2, Nº 4, 2004). This second volume is made up of contributions by colleagues and former students who wish to salute Francesc Calvet as an outstanding geologist and teacher. The papers included in this volume are also subjects in which Francesc was closely involved.

Fifth-order cyclicity and organic matter contents relationship (Lower Eocene, Pyrenees)

The Upper Limestone Member of the Corones Formation of the Spanish Pyrenees consists of various units (Lower and Upper Foraminifera Units, Shale Unit, Cherty-ostracode Unit, Ostracode Unit and Chara-ostracode Unit) and offers strong facies and lateral thickness (20 to 80 m) variations. Detailed facies analyses, fifth-order cycles and organic geochemical determinations in the central domain of the Corones platform carbonates (Cherty-ostracode Unit), lower Eocene in age, were carried out to establish a case of close relationship between variations in organic matter productivity and cyclicity with annual period. The Cherty-ostracode Unit displays a continuous and pervasive fifth-order cyclicity, represented by 5 cycles. Each cycle consists of a lower part (mollusc facies) and an upper part (laminated ostracode facies). The calculated fifth-order cycle period ranges from about 17,000 to 28,000 years, which falls within the Milankovitch Band. Variations in organic matter content related to these carbonate cycles have been established. The lower mollusc facies members show a low organic carbon content and Hydrogen Index (HI) below 0.6% in weight and 261, respectively. By contrast, the upper laminated ostracode facies members show high organic carbon contents (up to 2% in weight) and high HI (between 164 and 373), and are also characterized by important silicification processes (the content in chert is up to 30%). The organic geochemistry resulting from these organic rich levels reflects a contribution of algal marine input.

Los arenales costeros del cabo de Palos y de la isla Grossa (Murcia)

Mineralógicamente se distinguen tres grupos de arenales: costa de Poniente, costa de Levante e isla Grossa. Las playas de la costa de Poniente se caracterizan por la presencia constante de dolomita, hornblenda y por los minerales opacos. Costa de Levante es ms rica en especies mineralógicas que la costa de Poniente, dominando la dolomita, los piroxenos y la turmalina; y en la isla Grossa predominan los piroxenos, especialmente la enstatita. La proporción de carbonatos es muy elevada en todas las muestras, 20-50 %. Domina en las playas de la costa de Poniente la arena de grano grueso, y en las playas de Levante e isla de Poarena fina. Los cantos son abundantes en las playas de Poniente y estn presentes en las de Levante. Cabo de Palos parece actuar de barrera, separando dos provincias petrogenticas.

Siluro-Devonian graptolite stratigraphy of the Catalonian Coastal Ranges

Two facies characterize the Silurian and lower Devonian of the Catalonian Coastal Ranges, namely euxinic and pelagic carbonate facies. The first, is represented by black shales in which the atavus, acinaces, cyphus, triangulatus, convolutus, ?sedgwickii, ellesae and tumescens zones have been recognized. The graptolite succesion is far from complete on present evidence, but this is probably due to unfavorable environmental (taphonomic) conditions. This facies is similar to that prevailing throughout the Iberian massif and most of western Europe. The pelagic carbonate facies is peculiar to the Pridoli and lower Devonian and corresponds to the facies type prevailing in the Western Mediterranean Area. It is characterized by the nodular texture of limestones and marls, with all gradations between nodular limestones, marls and slates. Massive nodular limestone, occur in the lower part of the sequence (La Creu Formation) while the alternation of limestones, marls and slates charaterizes the upper part (Olorda Formation). Orthoconic cephalopds, crinoids, conodonts and tentaculites are the most common fossils present; graptolites occur in some shale horizons in the lower part of the Olorda Formation. These graptolites give strong indications of the uniformis and hercynicus zones (Lochkovian). The uppermost part of the sequence has not provided any graptolite fauna, but according their dacrioconarid fauna it corresponds probably to the Pragian.

El Paleozoico de les Guilleries

El macizo de Les Guilleries está formado por materiales metasedimentarios e ígneos de edad paleozoica. Los niveles mas bajos que afloran han sido atribuidos al Cambro-Ordovícico y consisten en dos tramos esencialmente pelíticos bien diferenciados separados por un nivel de ortogneises de varios centenares de metros de espesor. Por encima, se situa una serie vulcano-detrítica, con abundantes niveles de rocas volcánicas ácidas, y que ha proporcionado braquiópodos de edad Caradoc. El Silúrico y el Devónico, muy fragmentarios han sido también datados mediante fósiles. Toda la sucesión fue deformada y metamorfizada durante la orogenia herciniana. La deformación es polifásica y ha dado lugar al desarrollo de foliacions generalizadas en el brea. En las zonas mis profundas, la foliación regional es una crenulación que pliega una foliación anterior. En las zonas mas superficiales solo se observa una foliación de tipo ccslaty cleavagen. El metamorfismo hercinico afecta en mayor o menor grado a toda la serie. En las zonas mis profundas alcanza la facies anfibolitica de alto grado, con el desarrollo en las metapelitas de cordierita y feldespato potásico, mientras que en las zonas más superficiales s610 se alcanza la formación de clorita. En la región se han producido una serie de intrusiones ligadas a la orogenia herciniana. Las mis antiguas son unos filones de diorita y cuarzodiorita que se encuentran intensamente deformados. Posteriormente se produjo la intrusión de leucogranitos de dos micas, que son muy abundantes en las zonas más metamórficas y que en ocasiones se encuentran también algo deformados. Finalmente, se elnplazaron 10s granitoides tardios, que han originado extensas aureolas de metamorfismo de contacto.

Paleozoic stratigraphy of the Central and Northern part of the Catalonian Coastal Ranges (NE Spain)

The Paleozoic stratigraphic succession in the Catalonian Coastal Ranges spans the interval from Cambrian(?) to Carboniferous, with only one break, separating the pre-Carboniferous part of the sequence from the Carboniferous. The oldest rocks exposed form a sequence of schists, fine grained sandstones, gneisses (laminar pre-Hercynian intrusions), marbles, orto- and para-amphibolites and calcsilicate rocks. comparison with other localities iuggests an Early Cambrian age (or perhaps in part older). Upwards the sequence becomes more monotonous andconsists only of schists (or slates where themetamorphic grade is lower) and thin fine-grained sandstone layers (Cambrian-Ordovician). Still higher in the sequence, an altemation of greywackes and slates is found, with interlayered mud-supported conglomerates at its lower part and acid volcanic rocks which occur throughout the whole sequence. This part of the sequence has provided the oldest faunas known in the Catalonian Coastal Ranges, which indicate the Caradoc. Finally, in its uppermost part, the Ordovician sequence contains some thin limestone layers that contain Ashgill faunas. The Silurian, from Llandovery to Lower Ludlow, consists of black graptolitic shales with dolerite sills, whilst the upper Ludlow, Pridolian and Devonian consist of nodular limestones and marls withpelagic and hemipelagic faunas. The youngest Devonian faunas found correspond in general to the Emsian. The existence of a gap at this point of the sequence suggests the possibility that part of the Devonian could have been eroded. The Carboniferous is characterized by a thick culm sequence (Visean to Westphalian?), resting on thin chert and limestone layers (Tournaisian and Visean). A comparison with neighbouring areas shows a similarity regarding succession and facies with other Paleozoic massifs around the Western Mediterranean.

The Hercynian structure of the Catalonian Coastal Ranges (NE Spain)

In the Catalonian Coastal Ranges, Paleozoic sedimentary and meta-sedimentary rocks crop out in severa1 areas, intruded by late tectonic Hercynian granitoids and separated by Mesozoic and Tertiary cover sediments. Large structures are often difficult to recognize, although a general east-west trend can be observed on the geological map. Deformation was accompanied by the development of cleavages and regional metamorphism. Green-schist facies rocks are prominent throughout the Ranges, while amphibolite facies are restricted to small areas. In low-grade areas, the main deformation phase generated south-facing folds with an axial plane cleavage (slaty cleavage in metapelitic rocks). The intersection lineation (Ss/Sl) and the axes of minor folds trend cast-west, as do all mapable structures. Late deformations generated coarse crenulations, small chevrons and kink-bands, all intersecting the slaty cleavage at high angles. In medium- to high-grade areas no major folds have been observed. In these areas, the main foliation is a schistosity and is often folded, giving centimetric to decimetric, nearly isoclinal intrafolial folds. In schists, these folds aremuchmore common than inother lithologies, and can be associated with a crenulation cleavage. All these planar structures in high-grade rocks are roughly parallel. The late Hercynian deformational events, which gave rise to the crenulations and small chevrons, also produced large (often kilometric) open folds which fold the slaty cleavage and schistosity. As aconsequence, alternating belts with opposite dip (north and south) of the main foliation were formed. With respect to the Hercynian orogenic belt, the Paleozoic outcrops of the Catalonian Coastal Ranges are located within the northern branch of the Ibero-Armorican arc, and have a relatively frontal position within the belt. The Carboniferous of the Priorat-Prades area, together with other outcrops in the Castellón Province, the Montalbán massif (Iberian Chain) and the Cantabrian zone (specially the Pisuerga-Carrión Province) probably form part of a wide area of foreland Carboniferous deposition placed at the core of the arc.