Uranium geochemistry in groundwater from tertiary sediments

Dissolved U concentrations and activity ratios (ARs) of the U isotopes in the ²³⁸U decay series were measured in ground and surface waters as part of an investigation to delineate the water quality in a proposed uranium mining area of northwest Nebraska. In oxidizing groundwaters from 67 wells completed in the Tertiary sediments, increasing U concentrations in the direction of groundwater flow generally were associated with a maturation of the formation water as evidenced by evolutionary trends in major ion character. The increased U levels probably are associated with leaching as shown by the positive correlation between U concentrations and total dissolved solids (TDS) (r = +0.83). The inverse relationships between TDS and U ARs (r = ?0.73) and U levels and ARs (r = 0.72) indicate that the decay of excess U-234 is related to maturation of the formation water and to sediment leaching along the flowpath. The data are described by a model which incorporates etching, decay and recoil and suggests that aquifer residence time can be estimated from the TDS level.The levels of soluble U in a reducing uraniferous hydrogeologic unit near Crawford, Nebraska are affected by the proximity of the sample collection to ore. In groundwater samples having similar chemistries (Na-SO₄ + Cl type), similar Ehs, and collected from a close-knit pattern, U concentrations ranged from 0.01 to 2,037 μg l^?1 and ARs ranged from 0.75 to 12.6. This high variability in U levels and ARs is indicative of uranium ore in small areal studies where low ARs almost always are associated with high U concentrations.     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Evaluating the effects of catch-and-release angling on Cape stumpnose Rhabdosargus holubi in a South African estuary

Fisheries managers are increasingly promoting catch-and-release (C&R) to manage recreationally angled fish stocks. Despite this, there is a scarcity of information on the effects of C&R on estuarine-dependent species. Cape stumpnose Rhabdosargus holubi dominates the recreational fisheries catch and provides an important source of food for subsistence fishers in some temperate South African estuaries. The health and survival of R. holubi exposed to a C&R event was investigated by examining their physiological stress response (blood glucose and lactate), reflex impairment (reflex action mortality predictors [RAMP]) and short-term (12-hour) survival. Fish were captured and exposed to one of three air-exposure treatments: 0 s, 30 s or 90 s. Stress and health were measured either immediately (immediate) or one hour after (delayed) the C&R event. There was no significant difference in blood glucose between air-exposure treatments, but there was a significant difference between the mean immediate and delayed glucose levels within each treatment (F_(2,143) = 81.8, p < 0.01). In contrast, blood lactate level was significantly higher in the 90-s treatment (p < 0.05). Immediate blood lactate levels were significantly lower than the delayed samples for each treatment (F = 4.29, p = 0.02; n = 169). Although all fish exhibited at least one reflex impairment, the RAMP score was significantly higher in the 90-s air-exposure treatment (H_(2,86) = 9.73, p = 0.007). Also, RAMP scores were significantly lower in the delayed samples (p < 0.01). Although short-term mortality was relatively low (2.3%) for this species, it was highest in the 90-s treatment (7%). These results suggest that physiological stress is higher when R. holubi are exposed to longer periods of air exposure and that the physiological stress of fish subject to a C&R event is best measured after a delay.     

中国西部铂矿床类型与找矿方向探讨

中国铂矿资源严重不足,主要分布在中国西部,根据原生矿床特征可划分为4类：①硫化物型;②铬铁矿型;③辉石岩型;④层控型。寻找铂矿新类型和富铂(岩石)资源,应成为解决中国铂矿资源紧缺的重要任务。铂矿找矿方向：地台与地槽接合部位,特别是围绕着基性、超基性岩内外接触带,铂的预富集岩带与层控型铂矿带,另外还有砂铂型铂矿发育区有望扩大找铂前景。     

Possibilities of soil spectroscopy for the classification of contaminated areas in river floodplains

During the past decades, large amounts of diffuse contaminated soil material have been deposited in the floodplains of the river Rhine in the Netherlands. The dynamic character of this river causes a large spatial variability in the contamination level of its floodplain soils. Characterisation of the spatial variability exclusively based on soil sampling and analysis is often insufficient and expensive. Hyperspectral images can provide additional spatial information for a proper characterisation of the contamination situation of river floodplains. This paper describes the possible application of soil spectroscopy to estimate metal concentration levels in river floodplains. Soil reflectance spectra in the visible-near infrared region (VNIR) were measured in the laboratory for soil samples taken from two river floodplains along the river Waal, the main tributary of the river Rhine in the Netherlands. A multivariate calibration procedure using partial least squares (PLS) regression was applied to establish a relationship between reflectance spectra in the visible-near infrared (VNIR) region and spectrally active soil characteristics (organic matter and clay content) that are intercorrelated with concentration levels of Cd and Zn. Results of the analysis of two river floodplains are summarised and the influence of scale-level and sub soil material on the prediction capability is discussed.     

A New Octahedrite from South Africa

Abstract Examination of an iron meteorite found in South Africa discloses it to be a coarse octahedrite containing 6.90 weight-percent nickel. The meteorite body contains several inclusions of troilite, or troilite plus graphite, and at least one of pure graphite veined with kamacite. Kamacite, cohenite, and phosphides are the other major constituents of the structure.     

The Late Triassic microvertebrate fauna of Tytherington,UK

The Late Triassic fissure fills from the region of Bristol, SW England and S Wales, preserve unique assemblages of small vertebrates derived from an archipelago of palaeo-islands that document aspects of a critical transition in the history of terrestrial ecosystems. Tytherington Quarry, in south Gloucestershire, is the site of several fossiliferous fissures, all dated as Rhaetian (terminal Triassic), and source of abundant remains of the ‘Bristol dinosaur’, Thecodontosaurus antiquus. In addition, the fissure sediments have yielded previously unreported microvertebrate assemblages, including over 400 jaw remains from three genera of sphenodontians and 100 archosaur teeth assigned to 15 morphotypes. The land fauna is dominated by sphenodontians, with Diphydontosaurus by far the most common form, followed by Clevosaurus, then the sauropodomorph dinosaur Thecodontosaurus, and then the sphenodontian Planocephalosaurus. There are, in addition, rare remains of contemporaneous bony fishes, as well as fossils apparently reworked from the Carboniferous limestones, namely conodonts, holocephalian (chimaeroid) teeth, and a shark tooth. Many typical latest Triassic animals, such as temnospondyls, phytosaurs, aetosaurs, rauisuchians, plateosaurids and dicynodonts are not represented at Tytherington, perhaps because these generally larger animals did not live on the palaeo-island, or because their carcasses could not fit into the fissures. The absence of tritylodonts and early mammals is, however, less easy to explain on the basis of size, although it is known that these forms were abundant here by the Early Jurassic.     

Comparing object-based and pixel-based classifications for mapping savannas

The development of robust object-based classification methods suitable for medium to high resolution satellite imagery provides a valid alternative to ‘traditional’ pixel-based methods. This paper compares the results of an object-based classification to a supervised per-pixel classification for mapping land cover in the tropical north of the Northern Territory of Australia. The object-based approach involved segmentation of image data into objects at multiple scale levels. Objects were assigned classes using training objects and the Nearest Neighbour supervised and fuzzy classification algorithm. The supervised pixel-based classification involved the selection of training areas and a classification using the maximum likelihood classifier algorithm. Site-specific accuracy assessment using confusion matrices of both classifications were undertaken based on 256 reference sites. A comparison of the results shows a statistically significant higher overall accuracy of the object-based classification over the pixel-based classification. The incorporation of a digital elevation model (DEM) layer and associated class rules into the object-based classification produced slightly higher accuracies overall and for certain classes; however this was not statistically significant over the object-based using spectral information solely. The results indicate object-based analysis has good potential for extracting land cover information from satellite imagery captured over spatially heterogeneous land covers of tropical Australia.