Search

The facies and clay mineral study of clay/marl-rich levels from the Torrelapaja Formation (latest Hauterivian–early Barremian, NW Iberian Range, NE Spain) allowed to establish the palaeoclimatic and palaeoenvironmental conditions under they were generated. The muddy levels and pisoids contained therein of two logs were sampled and studied by X-ray diffraction and optical and electron microscopy. A similar mineralogical upwards trend is recorded in both logs, with a decrease in calcite coupled with an increase in quartz and orthoclase content and constant proportions in goethite, hematite, diaspore, anatase, rutile, ilmenite, and clay mineral content. The lower muddy levels have higher kaolinite content than the upper levels, where illitic phases are the dominant clay minerals. Smectite and intergrowths of illitic phases and kaolinite are also detected upwards. The kaolinite and smectite textures indicate an authigenic origin, whereas the illitic phases are former phases acting as a substrate for kaolinite crystallization. Pisoids mineralogy and texture show an in-situ origin, but some are fractured, indicating reworking processes. The mineral association found in the muddy levels is characteristic of oxisols formed under warm and humid conditions. The upward decrease in kaolinite content is coeval with an increase in the illitic phases and quartz content, related to siliciclastic input, but is also coeval with the presence of authigenic smectite. This indicates a decrease in chemical weathering, not fully registered due to the siliciclastic contribution, which was possibly associated with a change to colder, drier conditions during the latest Hauterivian–early Barremian in the studied area.

Ball clay deposits in the SE of the Iberian Range (NE Iberian Peninsula) consist of Albian clays and siltstones with greyish and blackish colors, interbedded with subbituminous coals. The ball clays are nowadays mined for the manufacture of white color ceramics. The mineralogy of these deposits consists mainly of kaolinite, illitic phases, and quartz. The euhedral to sub-euhedral morphology of the kaolinites suggests their in-situ origin. The anhedral morphology of the illites and the presence of frayed illites suggest a detrital origin. At the micro-scale, authigenic kaolinite booklets are observed filling pores and forming mica/kaolinite intergrowths, in which the kaolinite grows between the cleavage sheets of pre-existing detrital mica. At nanometer scale, illite/smectite (IS) phases are detected forming interlayers with mica and kaolinite, and evidence of the replacement of mica by kaolinite is observed. The matrix consists of defective illite and kaolinite, and random mixed layers of kaolinite-I/S (Kln-IS), illite-I/S (Ilt-IS), and I/S-smectite (IS-S). The textures of illite and the presence of different types of mixed layers suggest that the expandable phases and kaolinite are products of mica alteration. The effectivity of the alteration was probably a consequence of the low pH that occurred in the environment due to the presence of abundant organic- and acidic- rich fluids.

The Miocene Climatic Optimum (MCO) represents a global warm period (approximately 17–14.7 Ma) interrupting a long-term period of Cenozoic cooling. To elucidate if bauxitization took place in southeastern European mid-latitude areas during the MCO, we studied a section of undated massive karst bauxite (Crveni Klanac, CK) in central Dalmatia, Croatia, hosted in Upper Cretaceous limestones and overlain by Miocene Sinj Basin lacustrine deposits. Integrated mineralogical, morphological and geochemical analyses indicate the predominant mineral phases of the homogenous bauxite matrix are authigenic, subhedral to euhedral kaolinite and gibbsite. The in-situ mineralization was a consequence of pedogenic processes, indicating the CK bauxites formed autochthonously. In situ U–Pb zircon ages of the lower, middle and upper parts of the CK bauxite are very similar, dominated by Miocene and Oligocene ages, indicating that they all share similar protolith(s). Subsequent high-precision chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) analyses indicate a maximum depositional age (MDA) for the pre- bauxitic material of 16.9576 ± 0.021 Ma (2σ uncertainty, incorporating decay constant uncertainty). This MDA, a maximum age of autochthonous bauxitization, coincides with the onset of the MCO. Based on currently available geochronological constraints, the maximum timeframe for CK bauxitization was less than ~ 700 ka, which matches the records of the MCO in paleo- mid-latitude Europe. The potential imprint of pre- 17 Ma bauxitization and contribution of older (i.e., Upper Paleogene) bauxite deposits resedimented to the CK profile, as well as degree of potential parautochthonous origin of the CK bauxites, is yet to be investigated. More than simply aligning with regional and local reconstructions of continental climatic conditions during the onset and the early stages of the MCO, the high degree of autochthony of the CK bauxites provide a precise climatic constraint. For in-situ bauxitization to occur in the southeastern parts of mid-latitude continental Europe, paleoclimatic and paleoenvironmental conditions must have had mean annual temperature greater than 17–22 °C and mean annual precipitation of more than 1100–1200 mm.

We acknowledge the use of the LMA-INA (Universidad de Zaragoza) for access to dual beam equipment and expertise, the technical and human support provided by CICT of Universidad de Jaén (UJA, MINECO, Junta de Andalucía, FEDER), and the use of the PANalytical X'Pert Pro diffractometer of the Departamento de Mineralogía y Petrología, Universidad de Granada, Spain. María del Mar Abad is especially recognized for helping with the HRTEM work. The access to the HAADF FEI TITAN G2 microscope and the Philips CM20 (STEM) microscope was facilitated by the Centro de Instrumentación Científica of the Universidad de Granada. Thanks are extended to Javier Cuadros and an anonymous reviewer for their critical reviews and very helpful comments and suggestions., Glauconite and celadonite coexist at the nanometre scale in Early Jurassic submarine volcanic rocks of the Betic Cordillera (southern Spain) as a result of microbial activity. Samples from the limit between the two micas, recognizable in scanning electron microscopy, have been extracted using the focussed ion beam technique and studied by high-resolution analytical electron microscopy. Both micas are present as randomly oriented differentiated small crystals in the boundary area. They define clearly distinct compositional fields with gaps affecting to Fe, Mg and K. At the lattice scale, celadonite shows a high degree of order, with homogeneous orientation of the visible lattice parameters being a difference from glauconite, formed by packets no more than 10-layers thick. Smectite layers were also detected alongside glauconite packets, in accordance with X-ray diffractograms which indicate that glauconite is a mica-smectite interstratification being more than 90 % mica layers. The compositional gap indicates that celadonite is not the endmember of the glauconitic series and the two micas represent two different structural tendencies of mica, with glauconite having more distorted octahedral sheets, indicated by systematically higher b parameters than celadonite., MCIU-AEIFEDER PGC2018-094573-B-I00 ,PID2019-104624RB-I00 and RTI2018-093419-B-I00, Junta de Andalucia RNM-325, RNM-200 and RNM-179, Gobierno de Aragon E18_17R, European Fund

Found in the Upper Jurassic outcrops of Lourinha, Portugal, and first published in 1997, the Paimogo dinosaur egg clutch is one of Portugal’s most remarkable fossils, with over one hundred eggs preserved in association with embryonic bones, of the allosauroid theropod Lourinhanosaurus. However, many questions about it have remained unanswered, even until the present day. After its discovery, this extraordinary fossil became the keystone of a small local museum, greatly kick-starting regional tourism, while also holding the fossils in trust for future generations to study. More than 20 years later, continually sustained paleontological interest from the public has even given rise to both a highly successful dinosaur theme park in the region and an aspiring UNESCO Geopark. Recently, a multidisciplinary team of preparators, paleontologists, sedimentologists, mineralogists, and geochemists revisited an unopened jacket from the original excavation using an array of techniques to address various questions. Studies are ongoing, but the corpus of information obtained and the methodologies utilized to gather data have offered an opportunity to design an exhibit around the history of the Paimogo clutch, highlighting the scientific methods involved, and asserting the importance of preserving geological heritage for the future, when new tools will doubtlessly become available to provide yet another new look at old fossils. Here, we describe our analytical procedures and present an innovative exhibit designed to introduce to the public the latest advances on the research behind an iconic piece of Portuguese geoheritage, increasing its value both as a research item and as an educational resource.

Textural features are widespread in many soils, provide pedogenetic evidence, and are fundamental in soil classification systems. The presence of these features and their conservation over time require certain processes and soil forming factors. This study investigates the genesis of textural pedofeatures, especially clay coatings, and the stressful conditions that can eventually lead to their disappearance. To achieve this goal, four profiles with clay-enriched horizons have been studied (macro- and micromorphology, physical, chemical and mineralogical properties and classification) along a transect in the siliceous Iberian Chain (NE-Spain). The profiles, which have unmistakable illuvial accumulations in various horizons (Bhs, Bt, Btk), are classified (ST/WRB) as: a Spodosol/Podzol in the headslope, two Alfisol/Luvisols in the backslope and an Alfisol/Calcisol in the footslope. For the latter soil, the apparently strong difference in their classification to the first hierarchical level is due to the weight that the WRB places on the presence of an argic recarbonated horizon on a calcic horizon. Clay illuviation was identified in all the soils, with coatings and infillings of microlaminated clay. These clayey pedofeatures are mostly mechanically fragmented or deformed, which is micromorphologically evidenced by an undulating, wavy extinction that does not run completely parallel to the surfaces they cover. Different destructive processes are identified along the soil transect; so, cryoturbation is the dominant process in the Podzol located at the highest elevation (Moncayo Massif). Instead, the clay coatings in the Btk horizon of the footslope (Calcisol) are covered and deformed by the growth of secondary calcite. The textural pedofeatures in this soil, which is very clayey, can also undergo argilloturbation processes, like in the backslope soils (Luvisols). In conclusion, several ongoing stress processes, that sometimes require different environmental conditions (polygenetic), affect most textural pedofeatures and lead to their progressive alteration and disappearance. Different projects of the Research Results Transfer Office of the University of Zaragoza (Ref. 2017/0535, ref. 2018/0416; ref. UZ2020-TEC-01) provided financial support for this research.

Naturally and experimentally deformed gouges from sliding surfaces within the Galera Fault Zone were analyzed using scanning and transmission electron microscopy (SEM, TEM) to identify changes in the fault rocks as a consequence of ongoing deformation. The two gouges studied have a particular mineral association that includes planar (mainly smectite and illite) and fibrous clay minerals (sepiolite and palygorskite). Microstructural findings include a radical difference in grain alignment between the two gouges, a phenomenon that strongly influences gouge permeability. Smectite crystals are aligned on the same orientation and show a great number of layer terminations and delamination on the basal planes that contribute to a distributed mode of deformation in the gouge. In contrast, the sepiolite-rich gouge exhibits a grid-like microfabric that results in localized deformation limited to small areas where the needle-like crystals are bent and broken producing “feather-like” structures, without the presence of lattice distortions. Meanwhile, significant chemical results include: (1) Al content identified in sepiolite fibers through analytical electron microscopy (AEM), together with variability in the (110) d-spacing of sepiolite across single fibers, suggest the existence of a progressive transformation from sepiolite to palygorskite. (2) Mg content in smectite suggests that a portion of the smectites within the fault plane could have an authigenic origin and may be the result of a transformation reaction from palygorskite, however, the similarity of the 2:1 layer compositions between the smectites in the two contexts do not allow to either confirm nor deny such possibility. (3) Chemical continuity of Mg-decrease and Al+Fe-increase in the octahedral cation content of the sepiolites, palygorskites, and smectites within the gouges indicate a sequence of mineral transformations that is favored by a depleted Mg content and an increase of Al content in the fluid. In this setting, deformation promotes grain size reduction and fluid-rock interaction with the wall rocks resulting in a local supply of Al to the fault gouge that drives phase transformations. Structural differences between smectites and fibrous clay minerals affect important chemical and physical properties of the gouge including their mechanical properties. We propose that the permeability of the gouges in the Galera Fault is strongly affected by their mineralogy. Furthermore, the extent of the mineral authigenesis and mineral transformations could be a controlling factor that progressively changes both the permeability and the strength of the fault.

The present work analyses a set of cylinders manufactured by pressing and fired from 1000 °C to 1270 °C, which are composed of pure Al-rich rocks (bauxite) and mixtures of bauxite with Al–K-rich clays. The aim of the study is to determine the mineral and textural transformations that take place in the mixtures with firing and their influence on the physical properties of the final products in order to evaluate their refractory potential by comparing them with various fired commercial bauxites. To this end, raw and fired samples were analysed by X-ray diffraction, X-ray fluorescence, and optical and field emission scanning electron microscopy, and significant physical properties (e.g. density, linear shrinkage, porosity, colour, water absorption, thermal conductivity and point load resistance) were determined in the fired cylinders. The raw bauxite was mainly formed by boehmite, kaolinite and hematite whereas the illite- and kaolinite-rich clay was formed by quartz, illite and kaolinite. Kaolinite, illite and boehmite are not detected at 1000 °C and, from this temperature upwards, mullite, corundum, γ-Al2O3, hercynite, ilmenite, cristobalite and vitreous phase are formed. Changes in physical properties with rising temperature are associated with the mineralogical changes. The increases in density and linear shrinkage are related to the formation of vitreous phase and the crystallization of mullite, and correlate with the decrease in porosity, water absorption and thermal conductivity. The changes in the colour of the samples are related to the hematite content at each temperature, whereas the point load resistance is greater with higher corundum content. Both the firing temperature and the clay content play an important role in the refractory potential of the mixtures, since samples mixed with illite- and kaolinite-rich clay present similar properties at lower temperatures to those of the fired commercial bauxites.

The continental Paleocene-Eocene sequence investigated in this study belongs to the Salta Group, deposited in an intracontinental rift, the Salta Basin (NW Argentina), that evolved from the lower Cretaceous to the middle Paleogene, and is subdivided into the Pirgua, the Balbuena and the Santa Barbara Subgroups. The Maíz Gordo Formation (200 m thick) is the middle unit of the Santa Bárbara Subgroup, deposited during late post-rift sedimentation. We studied the mineralogy of fine-grained horizons of this formation by X-ray diffraction and Scanning Electron Microscopy (SEM) in order to examine the connection between vertical changes in clay mineralogy in alluvial sediments and paleosols, and global paleoclimatic changes registered during the Paleogene. Paleosols vary from calcic vertisols in the lowermost levels, to inseptisols and gleysols in intermediate positions, to gleyed oxisols in the upper section, indicating increased chemical weathering through time. Clay mineral relative abundances vary with a general increase in kaolinite content from bottom to top. However, at one site there are significant variations in kaolinite/muscovite (Kln/Ms) that define five cycles of kaolinite abundance and Kln/Ms. that indicate cyclic patterns of paleoprecipitation and paleotemperature. These are interpreted as several short-lived hyperthermals during the Paleocene-early Eocene in the Southern Hemisphere, which correlate with well-established episodes of warmth documented from the Northern Hemisphere. Fil: Do Campo, Margarita Diana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentina Fil: Bauluz, Blanca. Universidad de Zaragoza; España Fil: del Papa, Cecilia Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: White, Timothy. State University of Pennsylvania; Estados Unidos Fil: Yuste, Alfonso. Universidad de Zaragoza; España Fil: Mayayo, Maria Jose. Universidad de Zaragoza; España

The present study examines the micro- and nano-texture and composition of ammonium-bearing and potassium micas in very-low grade metamorphic black Silurian shales from the SE Iberian Range (NE Spain). Two organic-rich shales were studied by X-ray diffraction (XRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), analytical electron microscopy (AEM) and electron energy loss spectroscopy (EELS). The XRD showed the presence of two populations of micas: pure K micas with d001 = 9.98 Å and ammonium-bearing micas with larger d001 values (10.08 Å and 10.05 Å). The latter values indicate NH4 contents between 13 and 29% in the interlayer, which was confirmed by IR. Interstratifications of smectite and mica layers in the mica packets were not detected by XRD and TEM. Mica packets with sizes ranging from 100 to 250 Å show disordered polytypes and (001) lattice fringes that reflect the presence of K- and NH4-bearing layers (9.9–10.2 Å).The combination of AEM and EELS analyses on powdered and lamellar samples indicates that micas have typical dioctahedral compositions with highly variable K contents. This variation in K is consistent with the presence of K and NH4 in the interlayers, even though the NH4 and K are not distributed homogeneously; rather they are segregated in nm-sized domains in the mica interlayer.

The aim of this study has been to analyse the mineralogical and textural transformations of a set of aluminium-rich shales of interest for refractory and ceramic uses, fired from 800 °C to 1300 °C. To that end, raw and fired samples were analysed by X-ray diffraction, transmitted light microscopy, field emission scanning electron microscopy, and transmission electron microscopy. Raw samples comprise variable proportions of illite, pyrophyllite, orthoclase, quartz, kaolinite, mixed-layer I-Sm, and organic matter. At temperatures below 800 °C, kaolinite, mixed-layer I-Sm, and organic matter are destabilized, indicating that they are the least stable phases in the firing process. Illite, pyrophyllite, and orthoclase remain until 1000 °C and show a broader stability field during firing than in natural environments. Quartz persists throughout the entire firing process, although it is partly replaced by vitreous phase. Hematite crystallizes at 900 °C. Vitrification begins at 1000 °C, marking the first significant textural change. From 1000 °C mullite starts to crystallize from the Si- and Al-rich vitreous phase. The mullite composition is not stoichiometric and probably as temperature increases Si is partially replaced by Al, Fe and Ti in the structure. Nevertheless, with the increase of the firing temperature, the mullite composition is closer to the theoretical composition and also to that of natural mullites. Furthermore its crystal thickness increases with temperature up to 70 nm.

The Eocene continental sequence investigated in this study belongs to the Salta Group; it was deposited in an intracontinental rift, the Salta Basin (NW Argentina) that evolved from the Lower Cretaceous to middle Paleogene. The Salta Group contains the Maiz Gordo and Lumbrera Fms, spans the Paleocene-early Eocene, and shows excellent exposures in the region of the Valles Calchaquies. This research is focused on the continental facies of the Lumbrera Fm, which correspond to the early Eocene. We studied the mineralogy of the fine-grained beds of the Lumbrera Fm in five locations (Valle Encantado, Tonco, Tin Tin, Luracatao, and Obelisco) by X-ray diffraction and scanning electron microscopy in order to examine the vertical variations in clay mineralogy and their relations with global paleoclimatic changes registered during the Eocene. The microtexture of the authigenic smectite-type clays (Sm to I/Sm R0) suggests that they mainly originated by crystallization from glassy volcanic materials. The high reactivity of the glass precludes the use of smectite-type-clay formation as an indicator of specific paleoclimatic conditions in the studied sediments. In contrast, the formation of kaolinite in sections with very low smectite proportions and a strong degree of weathering in crystalline silicates reflects intense weathering conditions and is a useful paleoclimatic proxy in terrestrial sediments. Significant variations in kaolinite/muscovite ratios at the base and in an intermediate bed in the Lumbrera Fm at Valle Encantado suggest the presence of cyclic hyperthermals through the Ypresian stage that may be tentatively correlated with the Eocene Thermal Maxima 2 and 3, which are the largest events that have been identified at a global scale in early Eocene marine sediments.

The Spheroolithidae oospecies Guegoolithus turolensis, putatively attributed to non-hadrosauroid styracosterns was first described in the Barremian of the Iberian Basin, and later reported in the Valanginian–Hauterivian of the Cameros Basin, with both occurrences separated by a few hundred kilometres but by over 10 million years. Here we apply electron backscatter diffraction to search for crystallographic and ultrastructural differences between both occurrences of this ootaxon. Not only did not we found significant differences between eggshells from the two basins, probably laid by different non-hadrosauroid styracostern species but also, we found significant similitudes with the Late Cretaceous Maiasaura eggshells from North America. All Spheroolithidae eggshells are characterized by a profusion of low angle misorientation boundaries within larger orientation domains, that fan out from the eisospherite. A very quick reorientation of the c-axis of the crystals is observed, and explained partially via competitive growth. This conservative eggshell architecture suggests that the physical properties of the eggshell of styracosterns remain unchanged for at least 80 million years, implying similar nesting and breeding behaviours.

In this research, we have investigated the illitization process in Quaternary calc-alkaline volcanic and volcaniclastic rocks in the active Tinguiririca geothermal field (Andean Cordillera, central Chile). XRD, SEM, and HRTEM/AEM techniques have been used to establish the illitization sequence and evaluate the influence of the factors controlling the mineral reaction and kinetics at low temperature (T). Analysed samples were collected through a slimhole core up to 815 m deep in which the T was measured in situ (up to 230 °C at the bottom of the drill core). Textural information indicates that the dioctahedral clays have replaced most of the vitreous components. In contrast, plagioclase phenocrysts have only been partially and patchily albitized. The observed replacements imply dissolution-crystallization processes. The illitization sequence detected by XRD is apparently continuous from smectite to R3 I-S through R0 and R1, with a progressive increase in illite layers. HRTEM data show a similar illitization trend. However, the high-resolution images reveal that the clays are more heterogeneous than the XRD patterns suggest, with the coexistence of different types of dioctahedral clays at the sample level. They also indicate that the most abundant dioctahedral clays are smectite, R1 I-S, and illite. Therefore, the XRD patterns are probably the result of a mixture of these phases plus accessory I-S mixed layers with higher ordering (R > 1). Increasing T with depth would enhance the kinetic conditions necessary for illitization and also favour the dissolution of the vitreous K-rich component and, locally the albitization of plagioclases. Both processes release K, which, with the concomitant increase in T and K availability, enhances the crystallization of clays progressively richer in K. Thus, at T ≤ 85 °C smectite crystallizes, at T > 85 °C the conditions are appropriate for the crystallization of R1 I-S (with minor smectite + R0 I-S), up to T ≥ 175 °C, where illite is the most abundant and relatively stable phase.

The inclusion of iron compounds in teeth, which impart a red to orange colour to them, is a phenomenon shown by several groups of vertebrates in different periods of their evolution. Incisors from fossil and extant shrews and from extant rodents were sectioned and studied with the techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) to compare their structure and the distribution of Fe. The enamel in white- and red-toothed soricids has three layers; two of them are divided into two zones in the red-toothed species. However, the most external layer varies among taxa; it is well defined in Sorex but difficult to identify in the Early Pleistocene genera Beremendia or Dolinasorex. In the arvicoline rodent Terricola, only two layers can be defined, the outer of which is divided into two zones depending on the presence or absence of Fe. The Fe proportions in the larger soricids reach up to 45%, but in rodents only up to 10% (weight % with respect to Fe + Ca + P). The STEM study shows that in a fossil soricid the Fe phases form clusters of nanometric particles of very poor crystalline oxides or hydroxides surrounding the apatite crystals that form the enamel.

Two stratigraphic sections of carbonate sediments with significant thickness differences and without appreciable tectonic deformation were studied near the trough and on a threshold zone at the Álava Trough. Such characteristics make them appropriate to analyze the influence of a slow progression of the diagenesis over the original clay suite. X Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Analytical Electron Microscopy (AEM) techniques were applied in natural and alkylammonium-treated samples. Diagenesis slightly modified the clay mineralogy, the disappearance of smectite, and the variation in the content and ordering of the I/S mixed layer, with burial being the most noteworthy process. The total charge in the 2:1 expandable layers of smectite and I/S shows a slight increase, preferentially located on tetrahedral sheets, with depth. The data suggest a moderate diagenesis grade for the studied materials. The combination of techniques allowed identification of several types of detrital micaceous phases, as well-crystallized K-rich micas, Na-K micas, mica-chlorite stacks, and illites, with an expandable behaviour after the alkylammonium treatment. The total charge of illites did not change with diagenesis, suggesting their detrital origin. This research shows that the detrital assemblage masks the diagenetic evolution in the basin, which indicates the importance of the combination of different techniques to infer correctly the diagenetic grade in a sedimentary basin., This research was funded by the Spanish Government FEDER project CGL 2015-65404-R/BTE, CGL2016-75679-P, by the Basque Government project IT930-16, Research Group RNM-179 of the Junta de Andalucía and the Aragon Government project E18_17R.

We perform a multidisciplinary study of biotite porphyroblasts and veinlet infills hosted in Cambrian strata of the hanging walls from the NW-SE-trending Datos, Jarque and Daroca thrusts (Iberian Chains). Stratigraphic and microstructural crosscutting features indicate that a biotite isograd runs parallel to the southeastern transects of the three thrusts. The metamorphic grade reached in the southeastern edge of the Iberian Chains is clearly distinct from both the Cadomian epizonal metamorphism, exclusively recorded in the Ediacaran–basal Cambrian Paracuellos Group, and the Variscan anchizone metamorphism recorded throughout Cambrian–Devonian strata. During post–Variscan negative inversion tectonics, renewed K-metasomatism along the same thrusts led to crystallisation of geochemically similar biotites in parallel fissures and veins. 40Ar/39Ar ages are (i) latest Westphalian–to–Guadalupian (285.82 ± 23.75 Ma) for metamorphic biotite porphyroblasts affected by diffusion loss of Ar, including the Carboniferous–Permian transition within error; and (ii) Early Triassic (246.87 ± 5.36 Ma) for biotite occlusion in post–Variscan veinlets. The Iberian Chains represent the southeastern prolongation of the Cantabrian and West Asturian-Leonese zones. The latter displays a uniform eastward decrease in metamorphic grade, whereas the Iberian Chains exhibits a heterogeneous distribution of low-grade metamorphic conditions (chlorite zone). The local presence of the biotite isograd is linked to the higher tectonic gradients associated with the Daroca, Jarque and Datos thrusts, quite similar to the metamorphic isogrades recognized both in the northeastern edge of the Demanda Massif and the Novellana-Pola de Allande-Degaña Belt of the West Asturian-Leonese Zone. This distribution allows the identification of a broad NW-SE belt of biotite-in isograd-related synkinematic metamorphism, following the western contact of the Narcea Antiform, the Anguiano Thrust and the southeastern edges of the Daroca, Jarque and Datos Thrusts in the Iberian Chains. Based on Variscan structural style and metamorphic grades, the Datos Thrust links with the contact that separates the Cantabrian and West Asturian-Leonese zones of the Iberian Massif., Financial support was provided by projects CGL2013-46169-C2-1-P and CGL2017-87631-P from Spanish MINECO, the Regional Government of Aragón and the European Regional Development Fund (Grupos Consolidados: Geotransfer and Recursos Minerales).

A combined facies and clay mineralogy analysis of the continental succession recorded in the lower part of the Blesa Formation (early Barremian, Oliete subbasin, NE Spain) allowed us to specify the palaeoclimatic and palaeoenvironmental conditions under which this sedimentary record originated. Six outcrops including clays, clays/marls and dm-thick interbedded palustrine-lacustrine limestone levels were logged and sampled for X-ray diffraction and optical and electron microscopy analysis. The lower levels consist of red clays with abundant ferruginous pisoids (1–5 mm in size) and macropisoids (>5 mm), whereas the intermediate and upper levels are ochre and violet clays/marls with few or no pisoids. The pisoids normally consist of a nucleus and a cortex made up of several layers. Some pisoids have a fragment of a previous pisoid acting as a nucleus, indicating local re-working processes. Both the nucleus and the cortex are formed by hematite, goethite, variable contents of kaolinite, and minor proportions of ilmenite. Their texture and mineralogy show an in-situ growth. Interbedded limestone beds within the clay- and clay/marl-dominated levels are formed by micrite, microsparite and sparite. These limestones are cemented by kaolinite and they also have pisoids, indicating the occurrence of edaphic processes. The red clays have the lowest calcite content and the highest hematite, anatase, diaspore, goethite and kaolinite content. By contrast, the ochre and violet clays/marls have higher illite content. Smectite is only detected in the ochre clays/marls. This mineral association is characteristic of lateritic palaeosols, formed under warm and humid conditions. Kaolinite and smectite textures indicate that they are authigenic, whereas illite may be of detrital origin. The upward decrease in kaolinite, hematite, anatase, diaspore and goethite content, along with the increase in quartz content and the presence of smectite and illite, reflect a change from warm and humid conditions to drier and colder conditions during the early Barremian in the studied area.

A set of materials from Teruel (NE Spain), which includes a karst bauxite deposit overlain by an Albian (Lower Cretaceous) kaolin-rich clay succession, has been characterized from a mineralogical, textural and geochemical point of view. The materials under study were examined by X-ray diffraction, optical and electron microscopy and by inductively coupled plasma (ICP) optical emission spectroscopy (OES) and mass spectroscopy (MS). The bauxite is pisolitic and predominantly red and the overlying clay succession is mainly made up of grey claystones. Upper-section of the clay succession is a layer with carbonate nodules and scarce pisolith-like particles that can be distinguished. The studied materials are mainly composed of kaolinite, coupled with gibbsite and accessory boehmite in the bauxite. Gibbsite is also identified in the layer with carbonate nodules. Mineralogical data, kaolinite crystallinity and the Chemical Index of Alteration indicate that the layer with carbonate nodules has recorded a weathering event that was not as intense as the one that led to the in-situ formation of the bauxite deposit. The geochemical behaviour of the analysed elements, especially the REEs, also supports the existence of a weathering event recorded in the layer with carbonate nodules, given the similar trends observed in this layer and in the bauxite. The weathering led to REE + Y leaching, with the HREEs being less mobile than the LREEs, and thus the Albian clay succession, except the layer with carbonate nodules, shows a greater potential as source of these strategic elements. The research has revealed that redox fluctuation made a significant contribution to the distribution of Fe and Ce during bauxitization concerning the precipitation of Fe oxides and accessory minerals such as those of the goyazite-crandallite series.

Fil: Moreno Azanza, Miguel. Universidade Nova de Lisboa; Portugal. Fil: Moreno Azanza, Miguel. Universidad de Zaragoza; España Fil: Gasca Pérez, José M. Universidad de Zaragoza; España Fil: Gasca Pérez, José M. Provincia de Neuquén. Ministerio de Energía, Ambiente y Servicios Públicos. Dirección Provincial de Minería. Museo Provincial de Ciencias Naturales Prof. "Dr. Juan A. Olsacher"; Argentina Fil: Díaz Martínez, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentina Fil: Díaz Martínez, Ignacio. Universidad Nacional de Río Negro; Argentina Fil: Bauluz Lázaro, Blanca. Universidad de Zaragoza; España Fil: Canudo, José I. Universidad de Zaragoza; España Fil: Fernández, Arturo. Asociación de Amigos del Museo de Enciso; España Fil: Pérez Lorente, Félix. Universidad de La Rioja; España Here we describe the new fossil site of El Horcajo in the vicinity of Trevijano (La Rioja, Spain). It is located in the palustrine facies of the Enciso Group (Cameros Basin). This new locality has provided dozens of eggshell fragments, together with other vertebrate remains and charophyte fructifications, which allow dating of the locality as Valanginian-Hauterivian. Five ootaxa have being recognized: 1) the Spheroolithidae Guegoolithus turolensis; 2) a surprisingly thick Prismatoolithidae indet., with certain affi nities to the oogenus Sankofa, that may represent a new oogenus and oospecies for this oofamily; 3) the Krokolithidae Krokolithes sp.; 4) recrystallized ?Testudoolithidae eggshells; and 5) ?Geckoolithidae eggshells of uncertain affi nity. This oodiversity is similar to that of other eggshell microsites. The ootaxonomic list differs from the other Iberian locality of the same age, Pochancalo 1 (Villanueva de Huerva Formation, Zaragoza) in lacking sauropod and megalosauroid theropod eggshells, but shares the presence the ornithopod and coelurosaurian theropod eggshells with other younger microsites found in similar facies. The age of the new locality has immediate consequences for the tectono-sedimentary framework of the Cameros Basin, and the new data will need to be considered in future stratigraphical works. Furthermore, the reliability of eggshells as biostratigraphic markers is questioned, and the viability of Guegoolithus as a guide fossil for the lower Barremian is rejected. En este trabajo se describe el nuevo yacimiento fosilífero de El Horcajo en las cercanías de Trevijano (La Rioja, España). Se encuentra en facies palustres dentro del Grupo Enciso (Cuenca de Cameros). Este nuevo yacimiento ha proporcionado docenas de fragmentos de cáscara de huevo, junto con otros restos fósiles de vertebrados y fructifi caciones de carofi tas, que permiten datar el yacimiento como ValanginienseHauteriviense. Se han identificado cinco ootaxones: 1) Guegoolithus turolensis, de la oofamilia Spheroolithidae; 2) un Prismatoolithidae indet. sorprendentemente grueso y con afi nidades al oogénero Sankofa, que podría corresponder a un nuevo oogénero y ooespecie; 3) Krokolithes sp. de la oofamilia Krokolithidae; 4) cáscaras recristalizadas asignables con dudas a Testudoolithidae; y 5) cáscaras de afi nidad incierta, aquí asignadas con dudas a Geckoolithidae. Esta oodiversidad es similar a la de otros microyacimientos de cáscaras de huevo. La lista ootaxonómica difi ere de la obtenida en la otra única localidad de esta edad en Iberia, Pochancalo 1 (Formación Villanueva de Huerva, Zaragoza), por la ausencia de cáscaras de huevo asignables a saurópodos y terópodos megalosauroideos, pero comparte la presencia de cáscaras de huevo asignables a ornitópodos y terópodos celurosaurios con otros yacimientos más recientes que muestran facies similares. Este nuevo yacimiento tiene consecuencias inmediatas para el marco tectono-sedimentario de la cuenca de Cameros, siendo necesario considerar estos nuevos datos en futuros estudios estratigráfi cos. Además, se cuestiona la fi abilidad del uso de cáscaras de huevo como marcadores bioestratigráfi cos, ya que los nuevos datos ponen en duda la utilidad de Guegoolithus como fósil guía para el Barremiense inferior.

Altered iguanodontian dinosaur teeth have been studied to analyse the unusual replacement of biogenic apatite and to deduce how the alterations affect the preservation of these fossils. The fossils were recovered from alluvial lacustrine facies (Barremian, Early Cretaceous) in Teruel (Spain). Mandibular teeth and sediments were studied in hand sample, by X-ray diffraction (XRD) and by scanning electron microscopy (SEM). The combination of the different techniques shows that the teeth have undergone at least three pseudomorphic stages: (1) replacement of the organic component of the dentine and enamel by fluorapatite; (2) replacement of the fluorapatite by aluminium sulphate phosphate phases (crandallite–woodhouseite series); and (3) replacement of part of the tooth by gypsum and Al- and Fe-rich phosphates (vauxite) as a consequence of the superficial weathering of the fossil-rich outcrop. The presence of organic matter and sulphides in the host rocks was the main factor promoting the dissolution of the previous phases and crystallization of the new ones. This is the first description of the replacement of biogenic apatite in dinosaur teeth by aluminium and iron phosphates as a result of fossil diagenetic processes; these minerals are scarce in sedimentary environments and may have economic interest because they contain rare earth or radioactive elements. Additionally, our results indicate that, to ensure proper curating of the specimens from this fossil site, it is crucial to completely remove the host rock and strictly control storage humidity.

Four outcrops of Lower Cretaceous (Barremian) karst bauxites located in Teruel (NE Spain) were analysed. The deposits show a heterogeneous-chaotic lithostructure consisting of pisolitic bauxite blocks embedded in lateritic red clays filling karst cavities. The research has focused on the geochemical study of major, minor, and trace elements (including some critical to industry) of both the bauxites and clays. The objective was to investigate the bauxite precursor material and to characterize the system’s geochemical evolution. Geochemical analyses were carried out by inductively-coupled plasma optical emission and mass spectroscopy. An absolute weathering index has been calculated to estimate element mobility, assuming Ti as an immobile element and the Upper Continental Crust (UCC) as parent material. Further, selected samples were observed by field emission scanning electron microscopy. The data indicate that both the bauxites and red clays originated by intense chemical weathering from more mafic argillaceous sediments than the UCC. Ongoing weathering caused the bauxitization of the upper parts of the original profile, preventing the lower parts from being bauxitized, thus producing the ferrallitized clays underlying the pisolitic bauxites. Subsequent karst reactivation gave rise to the current lithostructure. Ferrallitization is related to Fe, Sc, and V enrichment. On the other hand, although bauxites are relatively enriched in some elements compared to clays, the more intense chemical weathering associated with bauxitization led to chemical homogenization and widespread element depletion. During the bauxitization, Al, Ti, Zr, Cr, and probably Hf and the critical element Nb behaved as more immobile elements in the system. Bauxitization also enhanced homogenization and depletion of the REE, which is more pronounced for the LREE. HREE trends seem to be partly related to the concentration of Ti oxides in the bauxites, whereas P-bearing phases, more frequent in the clays, control the LREE. Subsequent to bauxitization, partial kaolinization of the bauxite took place related to the circulation of acid solutions that also caused the karst reactivation. These late processes caused some Al depletion in the bauxites and enhanced Fe loss together with V and, to a lesser extent, Ge.

Four outcrops of Lower Cretaceous (Barremian) karst bauxites located in Teruel (NE Spain) were analysed to determine their mineral associations and genesis related to climatic palaeoweathering events and late superimposed kaolinization processes. The materials comprise metric-sized pisolitic blocks embedded in a clay-rich red groundmass. Fourteen samples were examined by X-ray diffraction, optical microscopy, scanning and transmission electron microscopy and the major elements were analysed by inductively-coupled plasma mass spectroscopy (ICPMS). The samples are composed of kaolinite, gibbsite, goethite, and hematite as the main phases, with diaspore, boehmite, anatase, and rutile as accessory minerals. The results show a complex sequence of mineralogical and geochemical processes that transformed the parent rock into the current bauxite materials. The clay-rich groundmass constitutes the lateritic parent material of the pisolitic bauxites. In the parent material authigenic kaolinite (e.g. vermicular kaolinite and kaolinite between cleavage sheets of pre-existing mica) has been observed; Fe oxides formed subsequent to kaolinite. In the pisolitic bauxites, mineralogical and textural evidence indicates that bauxitization took place at the expense of previous kaolinite, with gibbsite post-dating the other Al hydroxides. The pisolitic bauxites also show a more homogeneous chemical composition and a relative Ti, Al and Zr enrichment. The data are consistent with an intense palaeoweathering event during the Lower Cretaceous (Barremian) under tropical climatic conditions (warm and humid). Several stages probably took place during the bauxitization process, suggesting variations in water saturation conditions. Subsequent karst reactivation stages and related collapses were responsible for the present lithostructure of the deposits and allowed late kaolinization not related to climate to take place. Copyright © 2014 John Wiley & Sons, Ltd.

A set of samples from the Camarillas Formation (Barremian, Weald facies) in the Galve Sub-basin (Central Iberian Chain, north-east Spain) was studied to determine the origin of the abundant kaolinitic clays and their relationship to the sedimentary environment, palaeoclimate and diagenetic processes. The samples were examined by X-ray diffraction and scanning and transmission electron microscopy, with special emphasis on clay-mineral characterization. The analysed materials are a mixture of detrital (quartz, micas, and K-feldspars) and authigenic phases (kaolinite, Fe-oxides, gibbsite, dickite, and calcite). Therefore, the mineralogy of the rocks reflects the source area, the sedimentary conditions, and the diagenetic evolution. The most abundant authigenic phases are kaolinites. The combination of XRD and electron microscopy shows that the kaolinites are well crystallized and have as high a degree of ordering as those formed by weathering in palaeosols; this clay formed the rock matrix, intergrowths with muscovite, and vermicular booklets that replaced detrital silicates as a consequence of intense dissolution processes. The diagenetic processes have recrystallized kaolinites in the sandstones, producing larger crystallinity indices and dickite. In contrast, kaolinites from the claystones and siltstones probably reflect formation by weathering. The kaolinitization process described, associated with the crystallization of gibbsite and iron oxides, is in agreement with the relatively warm and humid conditions described for the Iberian Range basin in the early Barremian.

The aim of this study is to analyze natural clinkers (= calcined clays by coal combustion) from a lower Cretaceous coal outcrop in Ari&ntilde, o (Teruel, NE Spain) in order to describe mineral and textural transformations produced during the spontaneous combustion of coal. To achieve this aim, samples were analyzed using X-ray diffraction and optical and electron microscopy. Spontaneous combustion resulted in the melting of the surrounding clays, with the generation of an Al&ndash, Si-rich vitreous phase. Subsequently, high-temperature phases crystallized from this vitreous phase. These new minerals are interesting due to their similarity with those formed during ceramic processes, used in the manufacture of stoneware and ceramic tiles, as well as in refractory ceramics, and with natural events such as metamorphic and igneous processes. The studied natural clinkers are composed of vitreous phase mullite, hematite, hercynite, cristobalite, quartz, pyroxenes, cordierite, gypsum, pyrite, and calcium oxides. A trend from hematite to hercynite composition indicates compositional variations at sample scale, which evidence d-spacing differences in hercynite and may be related to the Al and Fe content in hercynite depending on its texture. The mullite shows higher Si/Al ratio (1.21) than the theoretical composition (0.35), indicating that this mullite is more Si-rich. Three pyroxene-type compositions (diopside-type, ferrosilite-type, and a Ca&ndash, Al-rich pyroxene) were found. Both the mullite and the pyroxenes are nonstoichiometric.

We have developed a protocol for reconstructing 3D models of the skulls of extinct species of small mammals. For the first time, the reconstruction uses fragments of fossils from a mixture of different specimens and from related extant species. We use free software and commercial computers to make the process reproducible and usable for the scientific community. We present a semi-quantitative protocol to face the problem of making 3D reconstructions of fossil species that are incomplete in the fossil record and/or represented by a mixture of different individuals, as usually occurs with small vertebrates. Therefore this approach is useful when no complete skull is available. The protocol combines the use of microCT scan technology with a subsequent computer treatment using different software tools for 3D reconstruction from microCT and 3D design and printing (e.g. Fiji, SPIERS, Meshlab, Meshmixer) in a defined order. This kind of free and relatively simple software, plus the detailed description, makes this protocol practicable for researchers who do not necessarily have great deal of experience in working with 3D. As an example, we have performed virtual reconstructions of the skulls of two species of insectivore small mammals (Eulipotyphla): Beremendia fissidens and Dolinasorex glyphodon. The resulting skulls, plus models of the extant shrews Blarina brevicauda, Neomys fodiens, Crocidura russula and Sorex coronatus, make it possible to compare characteristics that can only be observed by means of microCT 3D reconstructions, and given the characteristics of the material, using this protocol. Among the characters we can compare are the position of the mandibles, the spatial relations among all the teeth, the shape of the snout and, in general, all parameters related with the anatomy of the rostrum. Moreover, these reconstructions can be used in different types of context: for anatomical purposes, especially to see internal features or characteristics at whole-skull scale, for bioengineering, animation, or other techniques that need a digital model.

The Upper Cretaceous outcrops of the Pyrenees yield one of the most extensive and continuous records of paleoological remains anywhere in the world. Most of eggs and eggshells have been referred to...

Abnormalities in the histo- and ultrastructure of the amniote eggshell are often related to diverse factors, such as ambient stress during egg formation, pathologies altering the physiology of the egg-laying females, or evolutionarily selected modifications of the eggshell structure that vary the physical properties of the egg, for example increasing its strength so as to avoid fracture during incubation. When dealing with fossil materials, all the above hypotheses are plausible, but a detailed taphonomical study has to be performed to rule out the possibility that secondary processes of recrystallization have occurred during fossilization. Traditional analyses, such as optical microscopy inspection and cathodoluminescence, have proven not to be enough to understand the taphonomic story of some eggshells. Recently, electron backscatter diffraction has been used, in combination with other techniques, to better understand the alteration of fossil eggshells. Here we present a combined study using scanning electron microscopy, optical microscopy, cathodoluminescence and electron backscatter diffraction of eggshell fragments assigned to Megaloolithus cf. siruguei from the Upper Cretaceous outcrops of the Cameros Basin. We focus our study on the presence of secondary shell units that mimic most aspects of the ultrastructure of the eggshell mammillae, but grow far from the inner surface of the eggshell. We call these structures extra-spherulites, describe their crystal structure and demonstrate their secondary origin. Our study has important implications for the interpretation of secondary shell units as biological or pathological structures. Thus, electron backscatter diffraction complements other microscope techniques as a useful tool for understanding taphonomical alterations in fossil eggshells. Fil: Moreno Azanza, Miguel. Universidad de Zaragoza; España Fil: Bauluz, Blanca. Universidad de Zaragoza; España Fil: Canudo, José Ignacio. Universidad de Zaragoza; España Fil: Gasca Pérez, José Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Provincia de Neuquén. Ministerio de Energía, Ambiente y Servicios Públicos. Dirección Provincial de Minería. Museo Provincial de Ciencias Naturales Prof. ; Argentina. Universidad de Zaragoza; España Fil: Torcida Fernández Baldor, Fidel. Museo de Los Dinosaurios, Salas de Los Infantes, Burgos; España

A set of fine-grained samples from a turbiditic sequence in a Southern Pyrenees foreland basin (Jaca Basin, Eocene) were studied to determine the influence of tectonics (Pyrenean Orogeny) on phyllosilicate recrystallization and infer the grade and basin maturity. The samples from four different outcrops were examined by X-ray diffraction (XRD) and by scanning (SEM) and transmission electron microscopy (TEM) with special emphasis on clay-mineral characterization (e.g.illitic phases). The analysed samples have simple mineral assemblages and consist of detrital quartz, albite and calcite, scarce clay matrix (mainly illite with chlorite), and calcite and dolomite cement. The lack of other phyllosilicates such as mixed-layer illite-smectite (I-S), pyrophyllite, Na-micas, or kaolin minerals is quite remarkable. On the SEM scale, samples (with marl composition) have poorly sorted textures and high detrital contents. In many cases they show bedding and/or cleavage, and in some cases neither is observed. Most of the clay-sized illites show very similar crystallinity and b0 values (determined by XRD) and distributions of crystallite thickness (measured by TEM) in all the outcrops, which is typical of late-diagenesis illites forming under low-pressure conditions. These illites are parallel (or subparallel) to bedding or randomly orientated. They are also characterized by disordered polytypes and low K contents. In some TEM images, a second type of illite has been observed. This secondary illite occurs parallel to cleavage, with thicker crystals (25–35 layers), K contents in the interlayer, and a 2M1 polytype. The pole figure analysis shows that most of the clays have (00l) planes parallel (or subparallel) to bedding although there are abundant clays with random orientation. There is no trend in the clay orientation/disorientation from the south to the north of the basin. All the data indicate that the strain rate associated with the Pyrenean Orogeny has not been recorded in the turbidite sequence controlling the relative orientation of clays, although anchizonal clay crystallization is favoured as a minor process.

The classical lower-middle Cambrian boundary is approximately equivalent with the boundary of the Cambrian Series 2 and 3, which is now in the process of definition by the International Subcommission on Cambrian Stratigraphy. Currently, there are two oryctocephalid trilobite species first appearance data (FAD) that are suggested as possible markers of this level: Ovatoryctocara granulata Tchernysheva, 1962 and Oryctocephalus indicus (Reed, 1910), respectively. Until now neither of these two species has been recorded in the Mediterranean subprovince or Baltica. As a result, in these regions a level potentially correlating with either the FAD of Ovatoryctocara granulata or Oryctocephalus indicus has to be located using the available bio-, isotope-, and event-stratigraphy data. Carbon isotope signatures reveal global oceanic perturbations adjacent to the Cambrian Series 2 and Series 3 (former lower-middle Cambrian) boundary. This event, first called the Valdemiedes Event (it was defined in Murero, NE Spain; Linan et al., 1993a), caused a noticeable extinction of trilobites, mostly olenellids and protolenids (which were replaced in some regions by paradoxidids), as well as an almost complete extermination of some other early Cambrian marine animals. Both isotope and palaeontological evidence show that the disappearance of olenellids in Laurentia, protolenids in Siberia and the appearance of the first Acadoparadoxides in Western Gondwana, Baltica, Avalonia, and Siberia, which was formerly thought to be a series of diachronous regional perturbations, were nearly contemporaneous events. Features of a global ecological crisis and faunal replacement being taken together with a pronounced global δ13Corg negative excursion would serve as the best indicator of the lower boundary of the Cambrian Series 3 and Stage 5 in the Mediterranean subprovince and is correlatable with the Ovatoryctocara granulata FAD. Another δ13Corg negative excursion followed by a positive shift occurs at a slightly younger level, which coincides with a transgression maximum and roughly is coeval with the Oryctocephalus indicus FAD, also proposed as a possible base of the Cambrian Series 3. Copyright © 2011 John Wiley & Sons, Ltd.

This paper focuses on the clay mineralogy (using XRD, SEM and TEM methods) of the lacustrine “Calizas de Torrente de Cinca” unit that represents the Oligocene-Miocene transition in the central part of the Ebro Basin (NE Spain). Phyllosilicates are mainly detrital although Mgsmectites could have been generated in the lake.Although a temperate, relatively humid climate dominated the source area during the Oligocene-Miocene transition (Chattian-Aquitanian), as deduced by detrital phyllosilicates assemblage, mineralogical vertical trends along with sedimentological studies indicate some changes.Relatively warmer and more humid conditions during the late Chattian, that favoured increasing chemical weathering, were replaced during the early Aquitanian by drier conditions coinciding with the Mi-1 glaciation effects; this change is coeval with a transition from deeper to shallower lacustrine facies.Phyllosilicate association analysis has also permitted an improvement in the palaeogeographical sketch and infers that the Pyrenees are the main source area for the lacustrine system.

A set of Silurian black shales from Sierra de Albarracín (NE Spain) corresponding to two different sections was studied to determine the relative influence of diagenesis, igneous activity, and regional tectonics on the clay-mineral genesis. The coexistence of pyrophyllite, I-S interstratifications (R1), ammonium-rich illite, potassium illite, kaolin, and chlorite is not the result of prograde evolution during diagenesis – very low-grade metamorphism. Three different stages may be inferred: (1) sedimentation of black shales (Aeronian, Lower Silurian, to basal Ludfordian, Upper Silurian) and the subsequent diagenetic process producing the coexistence of quartz, illite, kaolinite, organic matter, etc.; (2) intrusion of andesitic sills producing hydrothermal alteration and crystallization of pyrophyllite, ammonium-rich illites, smectite, I-S R1 phases and jarosite; and (3) and folding of shales and sills and development of penetrative schistosity during the late Variscan leading to illite and paragonite recrystallization reaching the anchizone grade.

The fissility and durability of representative samples of commercial roofing slates from ten deposits in the NW of Spain have been evaluated using transmitted and reflectedlight optical microscopy, scanning electron microscopy, chemical testing and geomechanical procedures. The dominant sulphides in the different slate samples are pyrite and pyrrhotite, the weathering potential of which can be highly variable. The dominant carbonate mineral is ankerite, which explains the low reactivity of these slates in acidic media. The minimum commercial plate thickness varies between 3.5 and 5 mm, depending on the microtexture of the rock. The methodology used in this paper is proposed in order to eliminate the subjectivity of input data that are used in current methods of evaluation and modelling of slate deposits, thus producing an improvement in the profitability of mining operations and a reduction in waste materials.

Geochemical analysis for the Mesoproterozoic clastic sedimentary rocks of the basal Gulcheru Formation of the Cuddapah Basin in the Gugudu-Dadithota-Parnapalle-Palkonda region (extending atleast 40 km) have been performed to highlight their provenance and weathering history. The low K 2 O/Al 2 O 3 ratios of the representative samples points to the recycled nature of sediments and illite clay in the sediments indicate an overall cold climate (low chemical weathering degree). All the provenance diagrams indicate a mixed source of the Gulcheru sediments with felsic dominancy and Upper continental crust (UCC) signature.

This paper presents a multidisciplinary approach (stratigraphic, sedimentologic, structural, and mineralogic) to document the evidences for Cadomian and earliest-Cambrian tectonic processes recorded in the Iberian Chains, which were strongly overprinted during Variscan and Alpine deformation episodes. The contact of the Neoproterozic Paracuellos Group and the lower Cambrian Bambola Formation is commonly identifiable by the presence of a distinct erosive unconformity related to the onset of alluvial plain sequences, or associated with synsedimentary faults. A meso-structural analysis of the deformation recorded in the Paracuellos slates reveals the existence of an earlier slaty cleavage (S 1N ) overprinted by Variscan contractional structures, some of them related to positive inversion of pre-Variscan normal faults. The comparative geometrical study with structures observed in the Bambola Formation (essentially, a single, NW–SE to N–S striking cleavage S 1C ) is not conclusive about the record of the Cadomian orogeny. However, micro-scale deformation associated with the earliest cleavage is much more intense in the Paracuellos slates. In addition, the metamorphic grade and the pressure conditions of the lower Cambrian anchizonal shales contrast with the Neoproterozoic epizonal slates. Both observations are consistent with a Cadomian contractional deformation associated with a low-grade, intermediate-pressure metamorphism, absent in the overlying rocks. Postdating both processes, stratigraphically marked by a tectono-thermal discontinuity located at the Paracuellos/Bambola contact, the onset of the lowermost Cambrian Bambola Formation is accompanied by strong palaeogeographic transformations in the sedimentary basin, including: (i) a sharp relative sea-level fall leading to deposition of alluvial plain sediments; and (ii) an increase in sedimentation rates and tectonically induced subsidence at fault-bounded depressions. All these changes, together with the presence of normal or transtensional faults at the base of Bambola Formation, point to an earliest-Cambrian extensional regime similar to that described for other neighbouring post-Cadomian basins.

The kaolinite from Albian sedimentary deposits (Escucha and Utrillas Formations) of the Iberian Range (Spain) have been investigated. This research has shown the presence of different types of kaolinites (detrital and diagenetic) along with micaceous phases in these deposits. Detrital kaolinites show anhedral morphology, low crystallinity and a degree of ordering as well as the presence of interstratified smectite layers. They constitute the matrix of the claystones and siltstones and were probably formed as a consequence of intense weathering processes in the source area during the warm period of the early Cretaceous. Diagenetic kaolinites have been recognized in the sandstones and siltstones, with kaolinite growing between ‘expanded’ mica flakes and vermiform and euhedral kaolinite forming the matrix. They have euhedral morphologies, high crystallinity and a high degree of ordering. They grewin situas a response to incipient diagenesis by K-feldspar dissolution and/or organic acid-rich fluids derived from the maturation of organic matter in shales.

The Cambrian Drumian Carbon Isotope Excursion (DICE) and the Steptoean Positive Carbon Isotope Excursion (SPICE) have been so far reported in subtropical platforms: the DICE event is a large negative excursion in δ13Ccarb record that nearly coincides with the beginning of the Drumian (Cambrian Series 3), whereas the SPICE event is a large positive shift in δ13Ccarb identified close to the base of the Paibian (Furongian Series). The chemostratigraphic excursions have been recognized in carbonate-dominated platforms, and their application to mid- and high-latitude, siliciclastic-dominated platforms has been problematic. This paper offers, for the first time, a high-resolution stratigraphic analysis of this time span in a temperate-water platform (Montagne Noire, France) that recorded episodes of carbonate productivity in nearshore environments. Two sections were analyzed in detail: a complete Cambrian Series 3–Tremadocian succession, devoid of carbonate interbeds and paleogeographically located in the distal part of the platform (Pardailhan nappe), and a Furongian-Tremadocian succession, which has limestone interbeds and represents the proximal part of the platform (Minervois nappe). The lower part of the La Gardie Formation in the Pardailhan nappe displays background δ13Corg values of −22‰ punctuated by a large negative, middle Languedocian (regional substage) shift, peaking at −24.5‰. This negative excursion is similar to the DICE event reported close to the base of the Drumian, although the latter is exclusively based on δ13Ccarb values. Stable isotopes of δ13Ccarb and δ13Corg from both sections also indicate a common chemostratigraphic shift at the onset of the Furongian. In nearshore deposits of the Minervois nappe, the δ13Ccarb background values for the interbedded limestone strata of the Val d'Homs Formation gradually increase from −3‰ to −1‰ and are punctuated by a sharp increase in δ13Ccarb values to >3.0‰. By contrast, in basinal shales of the La Gardie Formation in the Pardailhan nappe, the δ13Corg background values decrease from −22‰ to −27.1‰. This trend is directly controlled by total organic carbon (TOC) contents and is interpreted to have been initiated by changes in the degree of biodegradation of organic matter, sulfate reduction, and methanogenesis before or soon after burial. Despite this overprinting and the very low degree of metamorphism reached by the shales, the δ13Corg background trend is also punctuated by a sharp positive shift in δ13Corg values to >4.0‰, similar to the SPICE event. In addition, the asymmetric shape of the SPICE excursion in the Montagne Noire shows evidence for the HERB event, a late Furongian negative carbon isotope excursion not yet accepted as a worldwide chemostratigraphic anomaly. The recognition of both chemostratigraphic shifts in mixed and clayey strata opens new possibilities of chemostratigraphic correlation in mid- and high-latitude platforms, where carbonate factories did not widely develop, and strata only contain endemic fauna. This implication has a major consequence because the Global Stratotype Section and Point (GSSP) of the Drumian and Paibian stages occurs near the base of both excursions.

Carbonate strata containing abundant euhedral feldspar, usually considered as authigenic, are characteristic of some lower Cambrian exposures in the Atlas Mountains, Morocco. Impure limestones are abundant in the Issendalenian Amouslek Formation of the western Anti-Atlas, and in the Banian Lemdad Formation of the southern High Atlas. Some of their limestone beds contain up to 40% acid insoluble residue, of which feldspar comprises as much as 65% in some samples, the remainder consisting of detrital and authigenic quartz, apatite, pyrite, and clay minerals. The host limestones are bioclastic tempestites, ooidal–oncoidal–bioclastic shoal complexes, archaeocyathan-microbial peri-reef settings (mainly flanks but not reef cores), and microbial reefs. A volcanic origin is adopted for the feldspars based on: (i) fluctuations in feldspar concentration paralleling bedding, but unrelated to host-facies (except for the aforementioned archaeocyathan-microbial reef cores that were controlled by turbidity); (ii) the local association with glassy fragments (with feldspars embedded in glass shards); and (iii) the scattered occurrence of gradational lithofacies from silty tuff to tuffitic limestone. The mineral and chemical composition of the host-rock and diagenetic fluids was the determining factor for the kind of feldspar preservation. Although the primary type of K–feldspar replacement is albitization, secondary albite subsequently suffered from illitization, chloritization, and/or replacement by calcite. A direct implication of this work is the possible geochronological dating of both volcanic eruptions and archaeocyath- and trilobite-bearing host-rocks based on radiometric analyses within unaltered K–feldspar pyroclasts extracted after etching.

Mineralogical and geochemical techniques have been used to determine the role of minerals in controlling the trace element composition of a set of clay-sized fractions from Albian siliciclastic rocks in NE Spain. These clay-sized fractions are composed of kaolinite and illite, minor quantities of quartz, and accessory heavy minerals. Kaolinite has a smaller crystal size than illite, accounting for its relative concentration in these fractions. The µm-sized heavy minerals are rutile, Fe-Ti- and Fe-oxides, zircon, pyrite, cassiterite, monazite and xenotime. Geochemical data indicate that most of the trace elements are relatively concentrated in clay-sized fractions, except for Zr, Hf, Y and HREE. Statistical treatment shows three different associations in the clay-sized fractions: (1) Rb, Cs and Ba with clay phyllosilicates, especially illite; (2) REE with Th, Y and P phases; and (3) Sc, Cr and V with Ti- and Nb oxides. Therefore, these data do not support the dominant REE control by clay mineralogy that other authors have reported.

This paper combines mineralogical data (X-ray diffraction, petrographic and scanning electron microscopy techniques) and geochemical analyses in order to investigate the composition of a set of samples (claystones, siltstones and sandstones) which belong to the Albian deposits of the Oliete Basin in Spain. The aims of the study are to characterize the distribution of major and trace elements in kaolinite-rich rocks; to infer the role played by accessory phases and clay minerals on the trace-element distribution; and to assess the source-area composition of these materials. Mineralogical analyses show that these rocks are mainly composed of different proportions of quartz and clay minerals (kaolinite and illite) with minor feldspar. Micron accessory minerals such as monazite, zircon, pyrite, marcasite, Fe oxides and Ti oxides have also been detected. The sandstone framework implies that the source area of these sediments was probably a granitoid source which underwent low rank metamorphism. The major element distribution reflects the mineralogy of the rocks. Plots in the A-CN-K diagram, as well as their CIA values, indicate that these sediments were generated from an intensely weathered source area. This produced the development of relatively cation-poor clays such as kaolinite, and claystones with large rare-earth elements (REE) contents. The fact that transition element contents in claystones are greater than in siltstones and sandstones suggests that they are preferentially linked to clay minerals, probably by surficial sorption. In comparison with other lithologies, the high abundances of high field strength elements in siltstones imply that accessory minerals, such as zircon and Nb-bearing phases, are mainly concentrated in siltstones. It should be noted that siltstones are also the lithology which displays the highest REE abundances. The statistical analysis of the geochemical data suggests that REE are mainly controlled by Ti- and Nb-bearing phases, such as titanite and Nb- and Ti-oxides. Although clay minerals are not the main phases in the REE control, they probably also have some influence, as the analyses show. In addition, other accessory phases such as monazite, secondary phosphates, and zircon also contribute to the REE contents, although much less than amorphous Fe oxides in some samples. According to the REE patterns and elemental ratios such as La/Sc, Th/Sc, Th/Co, etc., the source area of the studied outcrops was probably felsic and with intermediate composition between granite and granodiorite.