Weathering events recorded in uppermost Hauterivian–lower Barremian clay-dominated continental successions from the NW Iberian Range: climatic vs. tectonic controls

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.

Micro- and Nanotexture and Genesis of Ball Clays in the Lower Cretaceous (SE Iberian Range, NE Spain)

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.

Balance sedimentario del embalse de Ribarroja

The aim of this study was to build up a sediment budget of the Ribarroja Reservoir, which is located in the lower reach of the River Ebro. For this purpose, we analysed continuous discharge and suspended sediment transport data at several river sections entering the reservoir and at the dam outlet, for the period 2008-2011. The sediment load estimated upstream of the Mequinenza reservoir was 0.66×106 t a-1, whereas the estimated output was 0.04×106 t a-1. The sediment input coming from the large but highly regulated Pyrenean tributaries (Segre and Cinca) was 0.16×106 t a-1, whereas intermittent rivers naturally flowing from the Iberian Range (Matarraña and Algars) supplied an average load of 760 t a-1. The suspended sediment load trapped in the Mequinenza and Ribarroja reservoirs for the study period was estimated at 0.78×106 t a-1, which implies a reduction of ca. 95% of the sediment load of the river. The results illustrate the role of reservoirs in interrupting the sediment transfer in the lower reach of the Ebro, within a context of structural sediment deficit, following widespread land use changes (afforestation) that took place in the catchment after the 1940s.

Gene flow between diploid and tetraploid junipers - two contrasting evolutionary pathways in two Juniperus populations

Background Gene flow and polyploidy have been found to be important in Juniperus evolution. However, little evidence has been published elucidating the association of both phenomena in juniper taxa in the wild. Two main areas were studied in Spain (Eastern Iberian Range and Sierra de Baza) with both diploid and tetraploid taxa present in sympatry. Gene flow and ploidy level were assessed for these taxa and the resulted offspring. Results Twenty-two allo-triploid hybrids between J. sabina var. sabina and J. thurifera were found in the Eastern Iberian Range population. However, in the Sierra de Baza population no triploids were found. Instead, 18 allo-tetraploid hybrids between two tetraploid taxa: J. sabina var. balkanensis and J. thurifera were discovered. High genetic diversity was exhibited among the tetraploid hybrids at Sierra de Baza, in contrast to the genetically identical triploid hybrids at the Eastern Iberian Range; this suggests meiotic difficulties within the triploid hybrids. In addition, unidirectional gene flow was observed in both studied areas. Conclusion Polyploidy and hybridization can be complementary partners in the evolution of Juniperus taxa in sympatric occurrences. Juniperus was shown to be an ideal coniferous model to study these two phenomena, independently or in concert.

Genesis of an atypical Podzol in the Iberian Range: micromorphological characterization

A podzol has been described in the Iberian Range (Moncayo Natural Park), which may represent the southernmost example in Europe. The fact that it occurs at the podzol distribution limit makes its morphology atypical. The aim of this work is to identify the components and formation processes of the soil, and to determine if the processes are active or paleo-processes by a micromorphological approach. The study podzol is located in the top of a northern hillside (30% of slope), at 1600 m altitude on quartzitic sandstones, under Scots pine (<em>Pinus sylvestris</em>) with an udic moisture regime and a frigid temperature regime. We found opaque, orthic iron oxide nodules at the base of the profile (Bhs1), which is related to a current oxidation-reduction process; silt caps are also observed on the coarse elements, pedofeatures evidencing the cryoturbation process, probably also current processes. In the Bhs2 horizon, coatings and micro-laminated clay infillings are identified that are interspersed with fine silts in the holes. Many of these coatings are fragmented and mixed with the basal mass of the soil, indicating that they are paleofeature, possibly prior to the current podzolization.