Armeria castrovalnerana sp. nov., un nuevo taxon de Armeria gr. alpina en el macizo del Castro Valnera (Cordillera Cantábrica, Burgos)

Se describe una nueva especie del género Armeria (Plumbaginaceae) recolectada en el macizo del Castro Valnera (extremo oriental de la Cordillera Cantábrica). Se ha detectado una única población con no más de 190 individuos, en condiciones de extremo aislamiento geográfico y ecológico. La evolución reticular característica del género, que con frecuencia llega a producir microespecies de área muy reducida, aconseja que se tomen medidas de protección que aseguren su supervivencia

Corología de tres táxones de interés en el macizo del Castro Valnera: Eriophorum vaginatum L., Gentiana acaulis L. y Gentiana boryi Boiss

Se ofrece una visión actualizada de la situación en el macizo del Castro Valnera de tres especies de alto interés regional: Eriophorum vaginatum L., Gentiana acaulis L. y Gentiana boryi Boiss. Se comentan datos sobre la historia de su descubrimiento en ese macizo. Se recogen y enumeran para cada uno de ellos los datos de recolecciones, citas bibliográficas y de campo. Con el conjunto de todas ellas se elaboran varios mapas. Finalmente, se aportan comentarios que contribuyen al conocimiento de su comportamiento ecológico y se apuntan algunas pautas y criterios a tener en cuenta para su protección

Adiciones y revisiones al Atlas de la flora vascular silvestre de Burgos, VII

Se mencionan 73 táxones con citas y/o comentarios referidos a su existencia en la provincia de Burgos. De ellos 13 suponen una novedad para el catálogo provincial

Lu-Hf ratios of crustal rocks and their bearing on zircon Hf isotope model ages: The effects of accessories

All other factors being equal, the calculation of zircon Hf two stage model ages (TDM Hf) depends on the par- ticular Lu/Hf value assumed for the magmatic source, the effect being more pronounced as the age difference between zircon and magmatic source increases. It is generally considered that the Lu/Hf measured in the zircon- hosting rock does not represent the composition of the source because of potential garnet or zircon fractionation. Accordingly, most authors either assume a single fixed value for Lu/Hfsource, often Lu/Hf ≈ 0.079 to 0.108, or use two alternative models, one for felsic sources, often Lu/Hf ≈ 0.09, and the other for mafic sources, often Lu/ Hf ≈ 0.165. In contrast with these opinions, however, here we show that partial melting of peraluminous sources causes little decoupling of Lu from Hf because of similar solubilities of zircon and monazite. Furthermore, the effects of residual garnet are largely compensated by the numerous zircon inclusions that garnet and other residual minerals almost always contain. Partial melting of metaluminous sources may sig- nificantly decouple Lu from Hf if allanite and/or titanite are not present in the source, but the effect decreases as the melt fraction increases. Similarly, fractional crystallization of metaluminous magmas may decouple Lu from Hf if amphibole or clinopyroxene begin to crystallize before zircon saturation. The Lu/Hf distribution in 4784 rocks from different regions and ages is lognomal rather than normal, and the calculated medians, i.e. the maximum of the probability density function for the logarithmically transformed Lu/Hf, are Lu/Hfmafic rocks ≈ 0.08, Lu/Hffelsic rocks ≈ 0.05, i.e. notably lower than the above-mentioned felsic and mafic magmatic source averages. Magmatic sources may be remarkably heterogeneous with respect to Lu/Hf. Our calculations show that fixed Lu/Hfsource values translate the Lu/Hf heterogeneity of the source to the TDM Hf thus producing an artificial distribution of model ages that may be erroneously interpreted as different episodes of crustal growth. Therefore, we propose that the best strategy to calculate two stage Hf model ages of zircon is to use the analytically determined whole-rock Lu/Hf ratio as a proxy of the source. In the case of detrital or inherited zircons, for which no whole-rock information is available, it is advisable first to determine whether they come from a mafic or felsic rock by interpreting cathodoluminescence images, Th/U ratios and other chemical parameters, and then venture an estimate of the Lu/Hfsource from the SiO2 average

Adiciones y revisiones al Atlas de flora vascular silvestre de Burgos, X

Se mencionan 61 táxones con citas y/o comentarios referidos a su existencia en la provincia de Burgos. De ellos, 3 suponen una novedad para el catálogo provincial61 taxa with either quotations or remarks, related to their existence within the province of Burgos, are mentioned. 3 out of these aforementioned ones mean a valuable novelty for the provincial catalogue

Adiciones y revisiones al Atlas de la flora vascular silvestre de Burgos

Se mencionan 31 táxones con citas y/o comentarios referidos a su existencia en la provincia de Burgos. De ellos 8 suponen una novedad para el catálogo provincial.Additions and revisions for the “Atlas de la flora vascular silvestre de Burgos”, IX. 31 Taxa with either quotations or remarks, related to their existence within the province of Burgos, are mentioned. 8 out of these aforementioned ones mean a novelty value for the provincial catalogue