Exploring the joint compositional variability of major components and trace elements in the Tellus soil geochemistry survey (Northern Ireland)

The complexity of modern geochemical data sets is increasing in several aspects (number of available samples, number of elements measured, number of matrices analysed, geological-environmental variability covered, etc), hence it is becoming increasingly necessary to apply statistical methods to elucidate their structure. This paper presents an exploratory analysis of one such complex data set, the Tellus geochemical soil survey of Northern Ireland (NI). This exploratory analysis is based on one of the most fundamental exploratory tools, principal component analysis (PCA) and its graphical representation as a biplot, albeit in several variations: the set of elements included (only major oxides vs. all observed elements), the prior transformation applied to the data (none, a standardization or a logratio transformation) and the way the covariance matrix between components is estimated (classical estimation vs. robust estimation). Results show that a log-ratio PCA (robust or classical) of all available elements is the most powerful exploratory setting, providing the following insights: the first two processes controlling the whole geochemical variation in NI soils are peat coverage and a contrast between “mafic” and “felsic” background lithologies; peat covered areas are detected as outliers by a robust analysis, and can be then filtered out if required for further modelling; and peat coverage intensity can be quantified with the %Br in the subcomposition (Br, Rb, Ni).

Sedimentology, structure and age estimate of five continental slope submarine landslides, eastern Australia

Sedimentological and accelerator mass spectrometry (AMS) 14C data provide estimates of the structure and age of five submarine landslides (∼0.4–3 km3) present on eastern Australia's continental slope between Noosa Heads and Yamba. Dating of the post-slide conformably deposited sediment indicates sediment accumulation rates between 0.017 m ka–1 and 0.2 m ka–1, which is consistent with previous estimates reported for this area. Boundary surfaces were identified in five continental slope cores at depths of 0.8 to 2.2 m below the present-day seafloor. Boundary surfaces present as a sharp colour-change across the surface, discernible but small increases in sediment stiffness, a slight increase in sediment bulk density of 0.1 g cm–3, and distinct gaps in AMS 14C ages of at least 25 ka. Boundary surfaces are interpreted to represent a slide plane detachment surface but are not necessarily the only ones or even the major ones. Sub-bottom profiler records indicate that: (1) the youngest identifiable sediment reflectors upslope from three submarine landslides terminate on and are truncated by slide rupture surfaces; (2) there is no obvious evidence for a post-slide sediment layer draped over, or burying, slide ruptures or exposed slide detachment surfaces; and (3) the boundary surfaces identified within the cores are unlikely to be near-surface slide surfaces within an overall larger en masse dislocation. These findings suggest that these submarine landslides are geologically recent (<25 ka), and that the boundary surfaces are either: (a) an erosional features that developed after the landslide, in which case the boundary surface age provides a minimum age for the landslide; or (b) detachment surfaces from which slabs of near-surface sediment were removed during landsliding, in which case the age of the sediment above the boundary surface indicates the approximate age of landsliding. While an earthquake-triggering mechanism is favoured for the initiation of submarine landslides on the eastern Australian margin, further evidence is required to confirm this interpretation.

Gondwana break-up related magmatism in the Falkland Islands

Peer reviewed

Gondwana break-up related magmatism in the Falkland Islands

Peer reviewed

William Smith - 200 years of geomodelling celebrated at IAMG

The International Association for Mathematical Geosciences (IAMG) commemorated William Smith (23rd March 1769 - 28th August 1839) and 200 years of geomodelling with geological surveys and academics across the globe at the 17th annual conference of the IAMG in Freiberg, Germany from the 5th to 13th September 2015. The aim of the IAMG is to promote the use of mathematics, statistics and geoinformatics in the geosciences. The annual IAMG conference is an opportunity for geoscientists to collaborate with mathematicians and statisticians and present their recent work. The

17th annual IAMG conference, with 300 participants from across the world, differed from previous IAMG conferences in that it included a special ‘Day of Surveys’ to acknowledge 200 years of science and methodologies to construct maps.

Strength of the Iberian intraplate lithosphere: Cenozoic deformations and seismicity

Previous studies about the strength of the lithosphere in the Iberia centre fail to resolve the depth of earthquakes because of the rheological uncertainties. Therefore, new contributions are considered (the crustal structure from a density model) and several parameters (tectonic regime, mantle rheology, strain rate) are checked in this paper to properly examine the role of lithospheric strength in the intraplate seismicity and the Cenozoic evolution. The strength distribution with depth, the integrated strength, the effective elastic thickness and the seismogenic thickness have been calculated by a finite element modelling of the lithosphere across the Central System mountain range and the bordering Duero and Madrid sedimentary basins. Only a dry mantle under strike-slip/extension and a strain rate of 10-15 s-1, or under extension and 10-16 s-1, causes a strong lithosphere. The integrated strength and the elastic thickness are lower in the mountain chain than in the basins. These anisotropies have been maintained since the Cenozoic and determine the mountain uplift and the biharmonic folding of the Iberian lithosphere during the Alpine deformations. The seismogenic thickness bounds the seismic activity in the upper–middle crust, and the decreasing crustal strength from the Duero Basin towards the Madrid Basin is related to a parallel increase in Plio–Quaternary deformations and seismicity. However, elasto–plastic modelling shows that current African–Eurasian convergence is resolved elastically or ductilely, which accounts for the low seismicity recorded in this region.

Ar-40/-Ar-39 geochronology at the Instituto de Geociencias, USP: instrumentation, analytical procedures, and calibration

Laser heating Ar-40/Ar-39 geochronology provides high analytical precision and accuracy, mum-scale spatial resolution. and statistically significant data sets for the study of geological and planetary processes, A newly commissioned Ar-40/Ar-39 laboratory at CPGeo/USP, Sao Paulo, Brazil, equips the Brazilian scientific community with a new powerful tool applicable to the study of geological and cosmochemical processes. Detailed information about laboratory layout, environmental conditions, and instrumentation provides the necessary parameters for the evaluation of the CPGeo/USp Ar-40/Ar-39 suitability to a diverse range of applications. Details about analytical procedures, including mineral separation, irradiation at the IPEN/CNEN reactor at USP, and mass spectrometric analysis enable potential researchers to design the necessary sampling and sample preparation program suitable to the objectives of their study. Finally, the results of calibration tests using Ca and K salts and glasses, international mineral standards, and in-house mineral standards show that the accuracy and precision obtained at the Ar-40/Ar-39 laboratory at CPGeo/USP are comparable to results obtained in the most respected laboratories internationally. The extensive calibration and standardization procedures under-taken ensure that the results of analytical studies carried out in our laboratories will gain immediate international credibility, enabling Brazilian students and scientists to conduct forefront research in earth and planetary sciences.

Zircons, isotope ratios and element analyses from tonalite and oxide gabbro of the mid-ocean ridge from ODP Hole 176-735B

A limiting factor in the accuracy and precision of U/Pb zircon dates is accurate correction for initial disequilibrium in the 238U and 235U decay chains. The longest-lived-and therefore most abundant-intermediate daughter product in the 235U isotopic decay chain is 231Pa (T1/2 = 32.71 ka), and the partitioning behavior of Pa in zircon is not well constrained. Here we report high-precision thermal ionization mass spectrometry (TIMS) U-Pb zircon data from two samples from Ocean Drilling Program (ODP) Hole 735B, which show evidence for incorporation of excess 231Pa during zircon crystallization. The most precise analyses from the two samples have consistent Th-corrected 206Pb/238U dates with weighted means of 11.9325 ± 0.0039 Ma (n = 9) and 11.920 ± 0.011 Ma (n = 4), but distinctly older 207Pb/235U dates that vary from 12.330 ± 0.048 Ma to 12.140 ± 0.044 Ma and 12.03 ± 0.24 to 12.40 ± 0.27 Ma, respectively. If the excess 207Pb is due to variable initial excess 231Pa, calculated initial (231Pa)/(235U) activity ratios for the two samples range from 5.6 ± 1.0 to 9.6 ± 1.1 and 3.5 ± 5.2 to 11.4 ± 5.8. The data from the more precisely dated sample yields estimated DPazircon/DUzircon from 2.2-3.8 and 5.6-9.6, assuming (231Pa)/(235U) of the melt equal to the global average of recently erupted mid-ocean ridge basaltic glasses or secular equilibrium, respectively. High precision ID-TIMS analyses from nine additional samples from Hole 735B and nearby Hole 1105A suggest similar partitioning. The lower range of DPazircon/DUzircon is consistent with ion microprobe measurements of 231Pa in zircons from Holocene and Pleistocene rhyolitic eruptions (Schmitt (2007; doi:10.2138/am.2007.2449) and Schmitt (2011; doi:10.1146/annurev-earth-040610-133330)). The data suggest that 231Pa is preferentially incorporated during zircon crystallization over a range of magmatic compositions, and excess initial 231Pa may be more common in zircons than acknowledged. The degree of initial disequilibrium in the 235U decay chain suggested by the data from this study, and other recent high precision datasets, leads to resolvable discordance in high precision dates of Cenozoic to Mesozoic zircons. Minor discordance in zircons of this age may therefore reflect initial excess 231Pa and does not require either inheritance or Pb loss.

Lo local y lo global en la producción científica argentina con visibilidad en Scopus, 2008-2012 : Dimensiones nacionales e internacionales de la investigación

En Argentina, desde comienzos del presente siglo, las políticas científicas y tecnológicas explícitas evidencian un claro interés en la producción de conocimientos orientados a la resolución de problemas sociales, productivos y medioambientales de carácter local. Desde la bibliometría se vienen realizando estudios sobre la producción científica de los países, existiendo varios antecedentes que enfocan la atención en la producción científica argentina. Sin embargo, son incipientes y escasos los trabajos sobre la producción científica enfocada a temas locales. Los objetivos de esta investigación son analizar y describir la relación entre lo local y lo global en la producción científica argentina con visibilidad en Scopus en el período 2008-2012, y comparar indicadores de publicación, colaboración y liderazgo desde las dimensiones nacionales e internacionales de las prácticas de comunicación científica. Los resultados muestran ;que una cuarta parte de la producción está orientada a temas locales, con destacada presencia de contribuciones en Ciencias sociales, Economía y Administración, Ciencias agrícolas y biológicas, Ciencias de la tierra y relacionadas con el ambiente. Un alto porcentaje de esta producción se publica en revistas extra-regionales. Hay un mayor predominio de investigación en colaboración nacional y sin colaboración en los temas locales. Sin embargo casi un tercio de la producción se realizó en colaboración internacional, con diferencias porcentuales según las disciplinas. Por último, destaca el alto porcentaje de producción liderada por investigadores de instituciones argentinas en todas las disciplinas, tanto en los temas locales como globales

Lo local y lo global en la producción científica argentina con visibilidad en Scopus, 2008-2012 : Dimensiones nacionales e internacionales de la investigación

En Argentina, desde comienzos del presente siglo, las políticas científicas y tecnológicas explícitas evidencian un claro interés en la producción de conocimientos orientados a la resolución de problemas sociales, productivos y medioambientales de carácter local. Desde la bibliometría se vienen realizando estudios sobre la producción científica de los países, existiendo varios antecedentes que enfocan la atención en la producción científica argentina. Sin embargo, son incipientes y escasos los trabajos sobre la producción científica enfocada a temas locales. Los objetivos de esta investigación son analizar y describir la relación entre lo local y lo global en la producción científica argentina con visibilidad en Scopus en el período 2008-2012, y comparar indicadores de publicación, colaboración y liderazgo desde las dimensiones nacionales e internacionales de las prácticas de comunicación científica. Los resultados muestran ;que una cuarta parte de la producción está orientada a temas locales, con destacada presencia de contribuciones en Ciencias sociales, Economía y Administración, Ciencias agrícolas y biológicas, Ciencias de la tierra y relacionadas con el ambiente. Un alto porcentaje de esta producción se publica en revistas extra-regionales. Hay un mayor predominio de investigación en colaboración nacional y sin colaboración en los temas locales. Sin embargo casi un tercio de la producción se realizó en colaboración internacional, con diferencias porcentuales según las disciplinas. Por último, destaca el alto porcentaje de producción liderada por investigadores de instituciones argentinas en todas las disciplinas, tanto en los temas locales como globales

Lo local y lo global en la producción científica argentina con visibilidad en Scopus, 2008-2012 : Dimensiones nacionales e internacionales de la investigación

En Argentina, desde comienzos del presente siglo, las políticas científicas y tecnológicas explícitas evidencian un claro interés en la producción de conocimientos orientados a la resolución de problemas sociales, productivos y medioambientales de carácter local. Desde la bibliometría se vienen realizando estudios sobre la producción científica de los países, existiendo varios antecedentes que enfocan la atención en la producción científica argentina. Sin embargo, son incipientes y escasos los trabajos sobre la producción científica enfocada a temas locales. Los objetivos de esta investigación son analizar y describir la relación entre lo local y lo global en la producción científica argentina con visibilidad en Scopus en el período 2008-2012, y comparar indicadores de publicación, colaboración y liderazgo desde las dimensiones nacionales e internacionales de las prácticas de comunicación científica. Los resultados muestran ;que una cuarta parte de la producción está orientada a temas locales, con destacada presencia de contribuciones en Ciencias sociales, Economía y Administración, Ciencias agrícolas y biológicas, Ciencias de la tierra y relacionadas con el ambiente. Un alto porcentaje de esta producción se publica en revistas extra-regionales. Hay un mayor predominio de investigación en colaboración nacional y sin colaboración en los temas locales. Sin embargo casi un tercio de la producción se realizó en colaboración internacional, con diferencias porcentuales según las disciplinas. Por último, destaca el alto porcentaje de producción liderada por investigadores de instituciones argentinas en todas las disciplinas, tanto en los temas locales como globales

First Triassic tetrapod (Sauropterygia, Nothosauridae) from Castilla y León: evidence of an unknown taxon for the Spanish record

Several vertebrae of a sauropterygian specimen have been recovered in Fuencaliente de Medinaceli (Soria Province, Castilla y León, Spain). The remains come from Middle–Upper Triassic Muschelkalk Facies. This finding represents the first documented evidence of a Triassic tetrapod in Castilla y León. The vertebrae belong to Nothosaurus, a sauropterygian genus found in Europe, Middle East, North of Africa and China. This genus is poorly-known in the Iberian record. The new remains constitute the first evidence of the species Nothosaurus giganteus, or a related taxon, in the Iberian Peninsula. This study reveals the occurrence of at least two species of the sauropterygian Nothosaurus in the Spanish record.