Aligned olivine in the Springwater pallasite

The mechanism by which olivine grains became embedded within iron‐nickel alloy in pallasite meteorites continues to be a matter of scientific debate. Geochemical and textural observations have failed to fully elucidate the origin and history of the olivine crystals; however, little research attention has been devoted to their crystallographic orientations within the metal matrix. Using electron backscatter diffraction, we have collected crystallographic orientation data for 296 crystals within ～65 cm² sample surface from Springwater. Though no global crystallographic preferred orientation exists, very low misorientations are observed among [100] axes of olivine crystals within specific texturally defined domains. Combined with a thorough characterization of large‐scale Springwater textures, the definitively nonrandom spatial distribution of olivine orientations provides clues regarding the nature of the olivine's initial formation environment as well as the sequence of events subsequent to metal incorporation.     

Parametric uncertainty and sensitivity analysis of hydrodynamic processes for a large shallow freshwater lake

Abstract

A parametric uncertainty and sensitivity analysis of hydrodynamic processes was conducted for a large shallow freshwater lake, Lake Taihu, China. Ten commonly used parameters in five groups were considered including: air–water interface factor, water–sediment interface factor, surrounding terrain factor, turbulent diffusion parameters and turbulent intensity parameters. Latin hypercube sampling (LHS) was used for sampling the parametric combinations, which gave predictive uncertainty results directly without using surrogate models, and the impacts of different parametric distribution functions on the results were investigated. The results showed that the different parametric distribution functions (e.g. uniform, normal, lognormal and triangular) for sampling had very little impact on the uncertainty and sensitivity analysis of the lake hydrodynamic model. The air–water interface factor (wind drag coefficient) and surrounding terrain factor (wind shelter coefficient) had the greatest influence on the spatial distribution of lake hydrodynamic processes, especially in semi-closed bays and lake regions with complex topography, accounting for about 60–70% and 20%, respectively, of the uncertainty on the results. Vertically, velocity in the surface layer was also largely influenced by the two factors, followed by velocity in the bottom layer; the middle velocity had minimal impact. Likewise, the water–sediment interface factor (i.e. bottom roughness height) ranked third, contributing about 10% to the uncertainty of the hydrodynamic processes of the lake. In contrast, turbulent diffusion parameters and turbulent intensity parameters in the lake hydrodynamic model had little effect on the uncertainty of simulated results (less than 1% contribution). The findings were sufficiently significant to reduce the parameter uncertainties and calibration workload of the hydrodynamic model in large shallow lakes.

Editor Z. W. Kundzewicz; Associate editor S. Grimaldi     

A compromise aspect-adaptive cylindrical projection for world maps

There are two problems with current cylindrical projections for world maps. First, existing cylindrical map projections have a static height-to-width aspect ratio and do not automatically adjust their aspect ratio in order to optimally use available canvas space. Second, many of the commonly used cylindrical compromise projections show areas and shapes at higher latitudes with considerable distortion. This article introduces a new compromise cylindrical map projection that adjusts the distribution of parallels to the aspect ratio of a canvas. The goal of designing this projection was to show land masses at central latitudes with a visually balanced appearance similar to how they appear on a globe. The projection was constructed using a visual design procedure where a series of graphically optimized projections was defined for a select number of aspect ratios. The visually designed projections were approximated by polynomial expressions that define a cylindrical projection for any height-to-width ratio between 0.3:1 and 1:1. The resulting equations for converting spherical to Cartesian coordinates require a small number of coefficients and are fast to execute. The presented aspect-adaptive cylindrical projection is well suited for digital maps embedded in web pages with responsive web design, as well as GIS applications where the size of the map canvas is unknown a priori. We highlight the projection with a height-to-width ratio of 0.6:1, which we call the Compact Miller projection because it is inspired by the Miller Cylindrical projection. Unlike the Miller Cylindrical projection, the Compact Miller projection has a smaller height-to-width ratio and shows the world with less areal distortion at higher latitudes. A user study with 448 participants verified that the Compact Miller – together with the Plate Carrée projection – is the most preferred cylindrical compromise projection.     

A Review of “Policies for Sustainable Governance of Global Ecosystem Services”

The objectives are to (1) quantify, map, and analyze vegetation cover distributions and changes across Accra, Ghana, for 2002 and 2010; and (2) examine the statistical relationship between vegetation cover and a housing quality index (HQI) for 2000 at the neighborhood level. Pixel-level vegetation cover maps derived using threshold classification of 2002 and 2010 QuickBird normalized difference vegetation index images have very high overall accuracies and yield an estimate of 5.9 percent vegetation cover reduction over the study area between 2002 and 2010. A high degree of variance in vegetation cover for individual dates is explained by HQI at the neighborhood level, although minimal covariability between absolute or relative vegetation cover change and HQI for 2000 was observed.     

Scutocyamus antipodensis n.sp. (Amphipoda: Cyamidae) on Hector's dolphin (Cephalorhynchus hectori) from New Zealand

The whale‐louse Scutocyamus antipodensis n.sp., ectoparasitic on Hector's dolphin, Cephalorhynchus hectori (van Beneden), is described and figured from material collected in Cloudy Bay, Cook Strait, New Zealand. Morphologically the new species is very close to S. parvus Lincoln & Hurley, the type and only other species of the genus, known only from the North Sea. However, the two species differ in the detailed structure and spinosity of the body and pereopods.     

<Emphasis Type="Italic">Acacia mearnsii</Emphasis> management in a South African National Parks: SWOT analysis using hot topics in biological invasion as a guide

The assessment of the policy framework governing Invasive Alien Species (IAS) control is of critical importance in conservation. The undertaking of a SWOT analysis of such a framework is necessary because it enhances the efficacy of IAS control. The aim of this study is to carry out a SWOT analysis of the policy framework guiding the control of the spreading of Acacia mearnsii and other IAS in the Golden Gate Highlands National Park in South Africa, as well as the implementation of restorative measures in the park and adjacent communities in line with the recommendations of the Convention on Biodiversity. A comparative analysis of this framework and the hierarchical framework that was developed during the European Union Conference on Freshwater Invasives - Networking for Strategy in 2013 is undertaken. The results indicate the need to strengthen park-community relations, upgrade existing legislation, and boost the technical capacity of South African national parks to identify, detect, monitor and predict IAS invasions, both within the parks and their surroundings. This knowledge is important for developing future policies on IAS control in South Africa.     

Post-glacial climate change and its effect on a shallow dimictic lake in Nova Scotia,Canada

A high-resolution, multi-proxy lake sediment record was used to establish the timing of Holocene environmental change in Canoran Lake, southwest Nova Scotia, Canada. Proxies include %C, δ¹⁵N, δ¹³C, HI, magnetic susceptibility, and pollen. Canoran Lake is a small, shallow (11 m) lake with two ephemeral inlets and an outlet. The site was deglaciated at ca. 15,300 cal (calibrated) year BP and elevated %C values indicate the establishment of a productive aquatic environment that is consistent with Allerød warming. The Allerød was interrupted by rapid air temperature cooling during the Younger Dryas (ca. 12,900–11,600 cal year BP). The Early Hypsithermal (ca. 11,600–8,500 cal year BP) was relatively warm and wet. A slight increase in clastic input occurred between 9,100 and 8,500 cal year BP but δ¹⁵N, δ¹³C, and HI values imply that the lithostratigraphic response may not be indicative of climate-induced change. The strong proxy response between 8,500 and 8,000 cal year BP was likely due to cooling and drying coincident with the 8.2 k year event. The climate was relatively warm and dry during the Late Hypsithermal (ca. 8,000–3,500 cal year BP). None of the proxies’ exhibit notable change during the 5,500 cal year BP hemlock decline, indicating that ecological change was likely due to a pathogen attack. Post-Hypsithermal (modern) climate was characterized by an increase in precipitation and a decrease in air temperatures from ca. 3,500 to 700 cal year BP (top of core).     

Late superhumps and the stream–disc impact in IY UMa

We present two simple dynamical models for Sagittarius based on N -body simulations of the progressive disruption of a satellite galaxy orbiting for 12.5 Gyr within a realistic Galactic potential. In both models the satellite initially has observable properties similar to those of current outlying dwarfs; in one case it is purely stellar while in the other it is embedded in an extended massive halo. The purely stellar progenitor is a King model with a total velocity dispersion of 18.9 km s⁻¹, a core radius of 0.44 kpc and a tidal radius of 3 kpc. The initial stellar distribution in the other case follows a King profile with the same core radius, a slightly larger total velocity dispersion and similar extent. Both these models are consistent with all published data on the current Sagittarius system, they match not only the observed properties of the main body of Sagittarius, but also those reported for unbound debris at larger distances.     

U-Pb zircon systematics at Gruinard Bay, northwest Scotland: implications for the early orogenic evolution of the Lewisian complex

The Gruinard Bay area of the mainland Lewisian complex comprises a metamorphosed suite of Archaean trondhjemites and minor granites enclosing remnants of older tonalitic gneiss and mafic to ultramafic enclaves. The U-Pb zircon dating yields ages of 2731 ±14 Ma and 2728 ±2 Ma for two trondhjemite and 2732 ±4 Ma for one granite sample, also revealing the presence of large amounts of inherited xenocrystic zircons. Although the region has been pervasively overprinted by retrogressive events in amphibolite to greenschist facies, the textural relations between biotite, hornblende, quartz and titaniferous minerals indicate that these minerals are pseudomorphs of pyroxene and high-Ti amphibole formed in hornblende-granulite facies. Structural relations link this metamorphism to a steep northeast-trending fabric coeval with the intrusion of the trondhjemites, dated at 2730 Ma. Dating of zircon in amphibolite and tonalite enclaves yields complex internal isotopic relations with apparent ages ranging from 2825 to 2740 Ma. This age range reflects new growth during the 2730 Ma metamorphic/metasomatic events, superimposed on older zircon phases which include combinations of xenocrystic cores, and magmatic and/or metamorphic growth phases whose mode of formation cannot clearly be resolved by imaging techniques (e.g. cathodoluminescence) alone. A pegmatitic vein that escaped the D₃ strain and related isotopic disturbances yields a precise age of 2792 ±2 Ma, which constrains to some degree the earliest orogenic events in the area. Age relationships displayed in the central block at Scourie–Badcall, and in the Gruinard Bay area indicate that petrogenetic events in both areas were comparable about 2800 Ma and that both areas underwent trondhjemitic magmatism about 2730 Ma. In contrast, at Gruinard Bay there is no isotopic evidence for a period of high-grade metamorphism and magmatism at 2490–2480 Ma that drastically affected the Scourie block indicating that at this stage the two regions occupied different levels of the crust. Received: 23 October 1997 / Accepted: 20 July 1998