Geochemical and mineralogical record of the impact of mining on the Teign Estuary, Devon, UK

Previous mineralogical and geochemical studies on the sediments in the Teign Estuary, Devon, UK, have shown that there are elevated levels of barium present within the surface sediments and the river catchment due to historical mining. For this investigation, 8 shallow cores (<1 m) were recovered from various locations in the estuary. These cores were subsequently logged, photographed and divided into approximately 5 cm depth intervals. The geochemistry and mineralogy of 68 samples from the cores were analysed. Bulk sediment geochemistry was determined by XRF and data for Ba, Cu, Pb and Zn are presented here. The mineralogy of the samples was determined by XRD. In addition, the samples from two cores were selected for mineralogical analysis using automated SEM-EDS (QEMSCAN®). The data show a sediment depth related geochemical trend with typically the lowest concentrations of Ba, Cu, Zn and Pb at the bases of the cores. Several of the sampling sites reveal a marked peak in the concentration of Pb and Zn mid-core; however, Cu values are low and invariant throughout. Postdating the Pb-Zn peak, there is a subsequent elevation in Ba in many of the cores studied, at a sediment depth of between 10 and 20 cm. Maximum concentrations of Ba reach 3360 ppm; Pb, 2220 ppm; Zn, 887 ppm and Cu, 258 ppm. Detrital minerals present include: barite, rutile, ilmenite, zircon, monazite, pyrite, cassiterite, sphalerite, galena and chalcopyrite. Framboidal pyrite is the only diagenetic mineral observed. The geochemical results are consistent with the historical mining records in the catchment, with barite mining postdating Pb-Zn mining. Both episodes of mining have released particulate mine waste, which has accumulated within the estuarine sediments

The Godrevy dog; Early canine or lost pet ?

During sampling of the late Devensian St. Loy Member of the Penwith Formation at Godrevy, Cornwall, several ribs and vertebrae were discovered within the cliff face. The visible bones appeared in context with the surrounding geology with no evidence for later site disturbance or burial. During the excavation the skeleton was entirely enclosed within the coarse grained head deposits. The skeleton was articulated and nearly complete and is identified as Canis familiaris, the"domestic" dog. The recovery of this skeleton from the St. Loy Member of the Penwith Formation, generally regarded to be of mid to late Devensian age, is scientifically problematic. The accepted age for the late Devensian is 12-15,000 years BP. The oldest known domestic dogs are dated at about 10,000 years BP, although the burial of a dog or wolf puppy with a human skeleton from Israel 12,000 yrs BP is taken as early evidence of domestication. There are three possible interpretations: (1) the St. Loy Member of the Penwith Formation is younger than previously thought; (2) that Godrevy dog is a very early domestic dog; (3) that it is possible to incorporate a rcent articulated dog skeleton into Quaternary head deposits without any signs of physical disturbance at the site. Dating of the right radius bone by accelerator mass spectrometry has given a likely age for the skeleton of between 1620 AD and 1680 AD. Thus a 17th century domestic dog has been enclosed within Devensian coarse grained head deposits with no signs of disturbance to the site

Cool early Albian climates; new data from Argentina

Previous studies on the stable isotope geochemistry of dimitobelid belemnites from Antarctica and Australia indicated cool climatic conditions during the early Albian in the shelf seas around the Gondwanan margin. In this paper new analyses from diagenetically unaltered specimens of Dimitobelus cf. stimulus from early Albian deposits of the Rio Mayer Formation of Lago San Martin, southern Argentina are presented. Oxygen isotope values for diagenetically least altered samples give values ranging between d18O C0.07 and C0.96 vPDB, which equate to a mean palaeotemperature of 9.5 (C (assuming dw of 1.2& SMOW). These data are consistent with a model of cool early Albian shelf seas in the Southern Hemisphere.Facultad de Ciencias Naturales y Muse

Cool early Albian climates; new data from Argentina

Previous studies on the stable isotope geochemistry of dimitobelid belemnites from Antarctica and Australia indicated cool climatic conditions during the early Albian in the shelf seas around the Gondwanan margin. In this paper new analyses from diagenetically unaltered specimens of Dimitobelus cf. stimulus from early Albian deposits of the Rio Mayer Formation of Lago San Martin, southern Argentina are presented. Oxygen isotope values for diagenetically least altered samples give values ranging between d18O C0.07 and C0.96 vPDB, which equate to a mean palaeotemperature of 9.5 (C (assuming dw of 1.2& SMOW). These data are consistent with a model of cool early Albian shelf seas in the Southern Hemisphere.Facultad de Ciencias Naturales y Muse

Cool early Albian climates; new data from Argentina

Previous studies on the stable isotope geochemistry of dimitobelid belemnites from Antarctica and Australia indicated cool climatic conditions during the early Albian in the shelf seas around the Gondwanan margin. In this paper new analyses from diagenetically unaltered specimens of Dimitobelus cf. stimulus from early Albian deposits of the Rio Mayer Formation of Lago San Martin, southern Argentina are presented. Oxygen isotope values for diagenetically least altered samples give values ranging between d18O C0.07 and C0.96 vPDB, which equate to a mean palaeotemperature of 9.5 (C (assuming dw of 1.2& SMOW). These data are consistent with a model of cool early Albian shelf seas in the Southern Hemisphere.Facultad de Ciencias Naturales y Muse

Clustering in 18O - absolute determination of branching ratios via high-resolution particle spectroscopy

The determination of absolute branching ratios for high-energy states in light nuclei is an important and useful tool for probing the underlying nuclear structure of individual resonances: for example, in establishing the tendency of an excited state towards α -cluster structure. Difficulty arises in measuring these branching ratios due to similarities in available decay channels, such as ( 18 O, n ) and ( 18 O, 2 n ), as well as differences in geometric efficiencies due to population of bound excited levels in daughter nuclei. Methods are presented using Monte Carlo techniques to overcome these issues

Constraining the provenance of the Stonehenge 'Altar Stone': Evidence from automated mineralogy and U–Pb zircon age dating

The Altar Stone at Stonehenge is a greenish sandstone thought to be of Late Silurian-Devonian (‘Old Red Sandstone’) age. It is classed as one of the bluestone lithologies which are considered to be exotic to the Salisbury Plain environ, most of which are derived from the Mynydd Preseli, in west Wales. However, no Old Red Sandstone rocks crop out in the Preseli; instead a source in the Lower Old Red Sandstone Cosheston Subgroup at Mill Bay to the south of the Preseli, has been proposed. More recently, on the basis of detailed petrography, a source for the Altar Stone much further to the east, towards the Wales-England border, has been suggested. Quantitative analyses presented here compare mineralogical data from proposed Stonehenge Altar Stone debris with samples from Milford Haven at Mill Bay, as well as with a second sandstone type found at Stonehenge which is Lower Palaeozoic in age. The Altar Stone samples have contrasting modal mineralogies to the other two sandstone types, especially in relation to the percentages of its calcite, kaolinite and barite cements. Further differences between the Altar Stone sandstone and the Cosheston Subgroup sandstone are seen when their contained zircons are compared, showing differing morphologies and U-Pb age dates having contrasting populations. These data confirm that Mill Bay is not the source of the Altar Stone with the abundance of kaolinite in the Altar Stone sample suggesting a source further east, towards the Wales-England border. The disassociation of the Altar Stone and Milford Haven undermines the hypothesis that the bluestones, including the Altar Stone, were transported from west Wales by sea up the Bristol Channel and adds further credence to a totally land-based route, possibly along a natural routeway leading from west Wales to the Severn estuary and beyond. This route may well have been significant in prehistory, raising the possibility that the Altar Stone was added en route to the assemblage of Preseli bluestones taken to Stonehenge around or shortly before 3000 BC. Recent strontium isotope analysis of human and animal bones from Stonehenge, dating to the beginning of its first construction stage around 3000 BC, are consistent with the suggestion of connectivity between this western region of Britain and Salisbury Plain.This study appears to be the first application of quantitative automated mineralogy in the provenancing of archaeological lithic material and highlights the potential value of automated mineralogy in archaeological provenancing investigations, especially when combined with complementary techniques, in the present case zircon age dating

Análisis mineralógico integrado (Qemscan y Drx) de lutitas negras: los depósitos tithonianos basales de la Formación Vaca Muerta (Cuenca Neuquina, Argentina)

Se estudia la composición por difracción de rayos X y QEMSCAN (19 muestras) de fangolitas y margas de la Formación Vaca Muerta, acumuladas durante la transgresión tithoniana de la Cuenca Neuquina. Se definen importantes variaciones composicionales entre tipos litológicos y facies sedimentarias. Las rocas del sector marginal de la cuenca muestran fuerte influencia de los aportes terrígenos (cuarzo, feldespatos, illita e illita/esmectita). En las sedimentitas del sector depocentral (facies de pelitas grises oscuras) son importantes los indicadores de productividad orgánica (carbonatos y cuarzo biogénico), de condiciones anóxicas (pirita, siderita) y de un lento ritmo de acumulación sedimentaria. Los depósitos depocentrales de la transgresión tithoniana corresponden a la cocina de hidrocarburos de la Formación Vaca Muerta. Sus amplias variaciones mineralógicas ejercen fuerte impacto en la conversión de materia orgánica y en la liberación de gas y petróleo, así como en las propiedades petrofísicas y la fragilidad de rocas que constituyen la fuente principal para la explotación no convencional de hidrocarburos en la Cuenca Neuquina