Modern Sphagnumδ13C signatures follow a surface moisture gradient in two boreal peat bogs,James Bay lowlands,Québec

Carbon isotopic composition of Sphagnum macrofossils can potentially be used as a palaeohydrological tool for peat‐based climatic studies since a relationship between Sphagnum δ¹³C values and peatland surface moisture has been presented in previous studies. In order to verify this hypothesis, modern Sphagnum δ¹³C values were measured along a moisture (microtopographic) gradient in two boreal peat bogs. Isotopic measurements were performed on bulk material of S. fuscum, S. magellanicum, S. capillifolium and S. pulchrum. Isotopic variations found within and between Sphagnum species along the microtopographic gradient were compared using analysis of variance. A significant positive correlation (P < 0.0001) was found between Sphagnum δ¹³C values and their position along the surface moisture gradient. Results show that ¹³C‐depleted values are related to low water table depths (WTD), while ¹³C‐enriched values correspond to a water table that is close to the peat surface. Although the mechanisms underlying carbon fractionation processes in mosses are not well understood, we demonstrate that water resistance to CO₂ diffusion is an important fractionation process that is observed in bulk Sphagnum δ¹³C measurements, since drier and wetter samples exhibit consistent and very different isotopic signatures. Copyright © 2008 John Wiley & Sons, Ltd.     

On the vertical structure of the Rhine region of freshwater influence

An idealised three-dimensional numerical model of the Rhine region of fresh water influence (ROFI) was set up to explore the effect of stratification on the vertical structure of the tidal currents. Prandle’s dynamic Ekman layer model, in the case of zero-depth-averaged, cross-shore velocities, was first used to validate the response of the numerical model in the case of barotropic tidal flow. Prandle’s model predicted rectilinear tidal currents with an ellipse veering of up to 2%. The behaviour of the Rhine ROFI in response to both a neap and a spring tide was then investigated. For the given numerical specifications, the Rhine plume region was well mixed over the vertical on spring tide and stratified on neap tide. During spring conditions, rectilinear tidal surface currents were found along the Dutch coast. In contrast, during neap conditions, significant cross-shore currents and tidal straining were observed. Prandle’s model predicted ellipse veering of 50%, and was found to be a good indicator of ellipticity magnitude as a function of bulk vertical eddy viscosity. The modelled tidal ellipses showed that surface currents rotated anti-cyclonically whereas bottom currents rotated cyclonically. This caused a semi-diurnal cross-shore velocity shearing which was 90° out of phase with the alongshore currents. This cross-shore shear subsequently acted on the horizontal density gradient in the plume, thereby causing a semi-diurnal stratification pattern, with maximum stratification around high water. The same behaviour was exhibited in simulations of a complete spring–neap tidal cycle. This showed a pattern of recurring stratification on neaps and de-stratification on springs, in accordance with observations collected from field campaigns in the 1990’s. To understand the increase in ellipticities to 30% during neaps and the precise shape of the vertical ellipse structure, stratification has to be taken into account. Here, a full three-dimensional numerical model was employed, and was found to represent the effect of de-coupling of the upper and lower layers due to a reduction of mixing at the pycnocline.     

Far from Being "Home Alone": The Dynamics of Accompanied Fieldwork

Despite persistent images to the contrary, most fieldworkers are accompanied. Yet, there has been limited discussion on the nature of accompanied fieldwork, particularly by geographers. Drawing on our experiences in three countries in the tropics, we discuss the dynamics of being accompanied in “the field” by our children and female co‐researchers. Specifically, we focus on issues of access and rapport; the impacts of their presence on our positionality; and the implications these have for power relations and research outcomes. We demonstrate how being accompanied entangles our personal and professional selves and can result in more egalitarian power relations as we become “observers observed”. We argue that by paying attention to the dynamics of accompanied fieldwork, there is the potential to enhance the conceptual focus of our methodological concerns and to provide a more theoretically sophisticated mode of exploring the ways in which our multiple identities intersect while in “the field”.     

Variability of laboratory procedures and results in geoarchaeology

Many laboratory techniques are available to geoarchaeologists to determine physical or chemical attributes of sediment or soil samples, and several techniques are often available for analysis of a single attribute. This is illustrated by analyzing duplicate sediment and soil samples from the British Camp Site (Washington) and Lubbock Lake Site (Texas) using two methods for organic carbon content, two methods for organic matter content, and three methods for calcium carbonate content, and several pretreatment procedures for particle-size analysis. These comparisons illustrate that different methods of analysis for the same property of duplicate samples can yield different results. Therefore, when making comparisons with data from other sites or other investigators, the types of laboratory methods used in geoarchaeological analyses are important considerations. Choice of a particular technique will depend on a variety of factors, often conflicting, including the archaeological and geoarchaeological questions being asked, the physical and chemical nature of the samples, and the accuracy, efficiency, and cost of the method.     

A model for the growth and development of wave-dominated deltas fed by small mountainous rivers: Insights from the Elwha River delta,Washington

Observations from ground-penetrating radar, sediment cores, elevation surveys and aerial imagery are used to understand the development of the Elwha River delta in north-western Washington, USA, which prograded as a result of two dam removals in late 2011. Swash-bar, foreshore and swale depositional elements are recognized within ground-penetrating radar profiles and sediment cores. A model for the growth and development of small mountainous river wave-dominated deltas is proposed based on observation of both the fluvial and deltaic settings. If enough sediment is available in the fluvial system, mouth-bars form after higher than average river discharge events, creating a large platform seaward of the subaqueous delta plain. Swash-bars form concurrently or within a month of mouth-bar deposition as a result of wave action. Fair-weather waves drive swash-bar migration landward and in the direction of littoral drift. The signature of swash-bar welding to the shoreline is landward-dipping reflections, as a result of overwash processes and slipface migration. However, most swash-bars are eroded by the river mouth, as only 10 of the 37 swash-bars that formed between August 2011 and July 2016 survived within the Elwha River delta. The swash-bars that do survive either amalgamate onto the shoreline or an earlier deposited swash-bar, forming a single larger barrier at the delta front. In asymmetrical deltas, the signature of swash-bar welding is more likely to be preserved on the downdrift side of the delta, where formation is more likely and accommodation behind newer swash-bars preserves older deposits. On small mountainous river deltas, welded swash-bars may be more indicative of a large sediment pulse to the system, rather than large hydrological events.     

Nitrogen Mass Fraction and Stable Isotope Ratios for Fourteen Geological Reference Materials: Evaluating the Applicability of Elemental Analyser Versus Sealed Tube Combustion Methods

Thirteen commercially available silicate reference materials (RM) and one in‐house reference material, eleven of which have no previously published values, were analysed for nitrogen mass fraction and isotopic ratios with an Elemental Analyser (EA), and a Sealed Tube Combustion line, coupled to a continuous flow isotope ratio mass spectrometer (IRMS). These materials ranged from < 10 μg g^?1 to 1% m/m nitrogen mass fractions and δ¹⁵N of ?0.5 to +19.8‰. Existing nitrogen RM BHVO‐2, MS#5 and SGR‐1b were used to assess the accuracy of the data from the sealed tube combustion line, which was found to be in good agreement with existing published values. In contrast, the EA‐IRMS failed to fully liberate nitrogen from all silicate rocks and minerals (achieving a mean of 44 ± 10% nitrogen yield) resulting in kinetic fractionation of isotope values by ?1.4‰ on average. Therefore, sealed tube combustion is better suited for analyses of silicate‐bound nitrogen. The EA worked reliably for organic samples, but care should be taken when using the EA for silicate nitrogen research. Moving forward, it is recommended that BHVO‐2, Biotite‐Fe, FK‐N and UB‐N be used as quality control materials as they appear to be most reproducible in terms of nitrogen mass fraction (relative error < 10%, 1s), and isotopic composition (< 0.6‰, 1s).     

Mountain hazards and the resilience of social–ecological systems: lessons learned in India and Canada

Mountain regions are subject to a variety of hazardous processes. Earthquakes, landslides, snow avalanches, floods, debris flows, epidemics and fires, among other processes, have caused injury, death, damage and destruction. They also face challenges from increased populations, and expansion and intensification of␣activities, land uses and infrastructure. The combination of a dynamic bio- geophysical environment and intensified human use has increased the vulnerability of mountain social–ecological systems to risk from hazards. The ability of social–ecological systems to build resilience in the context of hazards is an important factor in their long-term sustainability. The role of resilience building in understanding the impact of hazards in mountain areas is examined and illustrated, in part, through examples from Canada and India. Resilient social–ecological systems have the ability to learn and adjust, use all forms of knowledge, to self-organize and to develop positive institutional linkages with other social–ecological systems in the face of hazards. The analysis suggests that traditional social–ecological systems built resilience through avoidance, which was effective for localized hazards. The more recent development and implementation of cross-scale institutional linkages is shown to be a particularly effective means of resilience building in mountain social–ecological systems in the face of all hazards.     

En(gender)ing the debate about water’s management and care - views from the Antipodes

In this paper, we map the gendered contours of contemporary water management in order to demonstrate that regimes for individual ownership of water rights, markets, and the productive use of water simply reinscribe and simultaneously submerge in their apparent gender-neutrality a normative masculinity that underpins economic globalization and fortifies existing power relations. Not only do such arrangements disadvantage reproductive values and non-consumptive users; more generally, they also lack the capacity to ensure water’s sustainable development. Consequently, new management institutions for sustainability are demanded and, in making a case for equity-enhancing and adaptive institutions that better reflect water’s materiality, its multiple values and emerging water scarcity, we argue the need to invoke the conserving and ecologically protective feminine principle. To support our reasoning, we analyse water reform processes instituted in Australia and specifically by the State of Tasmania, referring to the latter jurisdiction to illustrate the gendered nature of resource management and to underscore tensions between economic globalization and sustainability, concluding that the tensions between the two agendas are probably irresolvable. We position our work in the borderlands among gender studies, feminist geography and philosophy, and political ecology, drawing together insights about the construction of resource management, the possibilities of the feminine care ethic, and ideas about the characteristics of institutional systems that could ensure equitable allocation and sustainable use of the planet’s resources.     

Regional-scale Proterozoic IOCG-mineralized breccia systems: examples from the Wernecke Mountains, Yukon, Canada

A large scale Proterozoic breccia system consisting of numerous individual breccia bodies, collectively known as Wernecke Breccia, occurs in north-central Yukon Territory, Canada. Breccias cut Early Proterozoic Wernecke Supergroup sedimentary rocks and occur throughout the approximately 13 km thick deformed and weakly metamorphosed sequence. Iron oxide–copper–gold ± uranium ± cobalt mineralization is associated with the breccia bodies and occurs as veins and disseminations within breccia and surrounding rocks and locally forms the breccia matrix. Extensive sodic and potassic metasomatic alteration occurs within and around breccia bodies and is overprinted by pervasive calcite and dolomite/ankerite, and locally siderite, alteration, respectively. Multiple phases of brecciation, alteration and mineralization are evident. Breccia bodies are spatially associated with regional-scale faults and breccia emplacement made use of pre-existing crustal weaknesses and permeable zones. New evidence indicates the presence of metaevaporitic rocks in lower WSG that may be intimately related to breccia formation. No evidence of breccia-age magmatism has been found to date.