Dust climatology of Mildura,Victoria, Australia: transport direction

Large-scale geomorphic drivers that operate at continental scale are often climate driven. Changes in land use can accelerate wind erosion. The range of land management practises within one land use can have dramatic effect on ground cover and wind erosion. This study uses meteorological observations, land use, land management and dust concentration measurements of 129 dust events recorded between 1990 and 2007 to describe a dust chronology of Mildura, in south-eastern Australia. Frontal and frontal trough weather systems account for 74% of dust events. Furthermore, 88% of dust events come from rangelands in the northwest and the cropping lands to the southwest. The cropping areas to the southwest are the most common source of dust, accounting for 66% of events There is no relationship between rainfall and dust activity in this study, suggesting that land-management practices, especially on cropping lands, over-ride the controlling effect of rainfall. When cropping lands received above average rainfall in spring and summer during the 1990s, cultivation for weed control lead to rapid decline in ground cover that predisposed the land to wind erosion in following summer and autumn. In drought years, dust blows into Mildura from all directions suggesting that dust is climate driven rather than controlled by land use. © 2019 John Wiley & Sons, Ltd.     

Understanding the spatial distribution and physical attributes of upland swamps in the Sydney Basin as a template for their conservation and management

Temperate Highland Peat Swamps on Sandstone (THPSS) and Coastal Upland Swamps in the Sydney Basin (CUSSB) are listed as endangered ecological communities under Australia's national and state legislation. They are threatened by a range of human and climate impacts. Across the region there are 3208 individual, valley-bottom, elongate-shaped, upland swamps that drain first- or second-order drainage lines and small catchment areas (mean?=?0.25?km²). They occur at a median distance of 57?km from the coast in areas with an average annual rainfall of 1505?mm/year and average annual temperature of 15°C. Those closer to the coast occur on elevations as low as 160?m a.s.l., and those further from the coast, on plateau country, occur up to 1172?m a.s.l. (median 634?m a.s.l.). The valleys that contain these swamps terminate downstream at a valley constriction or bedrock step, behind which alluvial materials have accumulated, and peat has formed to produce relatively steep swamps (median slope 6.2 per cent). Understanding the spatial distribution and physical attributes of these systems, and having the accompanying maps as a resource, is critical for development of sound, well-informed conservation, rehabilitation and monitoring programs, and for analysing the ecosystem services they provide.     

Rehabilitation of Saline Wetlands, Olympics 2000 Site, Sydney (Australia)—I: Management Strategies Based on Ecological Needs Assessment

The Homebush Bay area, Sydney, site of the Olympic Games 2000, has been largely occupied for nearly a century by an abattoir, brickworks, armaments depot and waste dumps. However, it contains remnants of original ecosystems, including two estuarine wetlands, and the Olympic Co-ordination Authority (OCA), set up to manage the redevelopment of the site, is committed to the rehabilitation of these ecosystems. The ecological approaches and rehabilitation measures used for one of the wetlands are detailed. Apart from a history of disturbance, it has for 10 years been without tidal flushing. However, these wetlands are the largest remaining in the Sydney estuary, and are significant for a number of reasons including biodiversity and waterbird conservation. The ecological parameters of the site, the results of a ‘before-restoration-impact' study, and the iterative links between science and management in the introduction of the rehabilitation measures, are presented. Criteria for success are discussed, along with biomonitoring strategies to test success.     

Discordant ultramafic pegmatoidal pipes in the Bushveld Complex

Discordant ultramafic pipes cut most of the layered sequence of the Bushveld Complex. We have studied one pipe in detail, the Tweefontein pipe, which cuts the Critical Zone, eastern Bushveld Complex, because it is well-exposed in a new road cutting. Field relations suggest that these pipes were emplaced while the layered rocks were extremely hot and incapable of brittle failure. The existence of displaced chromitite and anorthosite fragments in this discordant body is suggestive of an intrusive magmatic, rather than metasomatic, mode of emplacement. Initial Sr isotopic ratios of plagioclase from the pipe are in the range 0.7073 to 0.7079, which contrast with typical ratios of 0.7055 to 0.7065 for the Critical Zone, and >0.708 for Main Zone. These data preclude an origin for the pipe as residual magmas from the adjacent layered rocks. The compositions of, and extensive exsolution in, pyroxenes in the pipe indicate temperatures of formation comparable to those of the layered sequence itself, and that they underwent slow cooling comparable to the surrounding layered rocks, such that they both have similar closure temperatures. Preferential replacement of leuconoritic layers suggests a temperature of emplacement in excess of the plagioclase–pyroxene cotectic temperature. The per mil δ¹⁸O difference between plagioclase and pyroxene (Δ_plag–px) for samples from within the pipes ranges from 0.4 to 1.0, and averages 0.7 (for nine pairs), compared to Δ_plag–px of 0.4 to 0.6 for host rocks, again consistent with magmatic temperatures of formation. Oxygen isotope ratios for plagioclase and pyroxene in the pipes and layered host rocks are comparable, and preclude a significant fluid contribution from metamorphosed sediments in the floor of the Bushveld Complex in the formation of the primary mineralogy. The presence of hornblende, and occasional higher Δ_plag–px values than in the normal layered sequence rocks suggest lower temperature equilibration in the pipe, probably in the presence of a fluid. Higher absolute δ¹⁸O values for both minerals in a few of the pipe and host samples suggest reaction with a later fluid. These discordant ultramafic pipes are considered to form by emplacement of magma batches, which are Sr-isotopically distinct from those which produced the adjacent layered rocks of the Bushveld Complex, but were nevertheless extremely closely related in time to the main intrusive events. Dissolution of host rocks, rather than purely mechanical dilation, provided the space for pipe emplacement. However, the pipe may have acted ultimately as a channelway for low-temperature hydrothermal fluids related to later faulting in the immediate vicinity. Received: 10 October 1998 / Accepted: 22 May 2000     

Inelastic instability of circular corrugated cylinders under external hydrostatic pressure

The paper presents an experimental study on six circular corrugated cylinders which were tested to destruction under external hydrostatic pressure. The results obtained from these vessels, together with the results obtained from elsewhere, were used to provide a design chart. The design chart appears to be suitable for designing these vessels to guard against inelastic instability.     

Geoarchaeologic analysis of South Platte River terraces: Kersey,Colorado

Soil-sediment records and radiometric dating allow the development of environmental histories of three South Platte River alluvial terraces in the vicinity of Kersey, Colorado. These advocate a correlation with Holocene glacial records for the Colorado Front Range (Benedict, 1981, 1985). The archaeological potential of the Kersey fill, the Kuner strath, and the Hardin fill depends upon their age and sediment context. The oldest and most extensive terrace is the Kersey fill. The position of cultural components on the Kersey terrace implies an association of older Paleoindian sites (11,500–10,000 B.P.) with channel banks and bars on the terrace, younger Paleoindian sites (<10,000 B.P.) with terrace margins near the river, and Archaic and younger sites with eolian deposits on the terrace. An association of Clovis components with both Kersey alluvium and adjacent eolian dune fields indicates that eolian deposition began prior to 11,000 B.P. and that sediment availability influenced early Holocene eolian deposition. Examination of 150 cores and 75 backhoe test units along an 8-km study corridor demonstrates that Paleoindian sites are not as abundant on the Kersey terrace as previous researchers have proposed. Although the incision of the Kuner strath began earlier than 9600 B.P., we propose that its greatest potential is to yield cultural components that postdate ca. 7250 B.P. In turn, the Hardin fill may yield cultural components dating to the Kuner abandonment (ca. 6380 B.P.). However, Hardin sediment and soil records recommend that this fill terrace's highest potential is to yield in situ cultural components dating from ca. 1900 to 120 B.P. © 1994 John Wiley & Sons, Inc.     

Ultraviolet sky radiance distributions of translucent overcast skies

Summary The diffuse sky radiation component in the ultraviolet wavelengths is often at least 50% of the global irradiance under clear skies, and is the dominant component of ultraviolet global radiation under translucent overcast skies. The distribution of sky radiance was measured in a rural area and modeled for wavelength bands of ultraviolet-B (UVB, 280–320 nm) and ultraviolet-A (UVA, 320–400 nm). Sky radiance measurements were made during the summer of 1993 over a wide range of solar zenith angles using radiance sensors mounted on a hand-operated hemispherical rotation mount. UVB irradiance measurements were also made during each scan. Since the ratio of measured irradiance under overcast skies and that predicted for clear skies was not correlated with cloud base height, opaque cloud fraction, or solar zenith angle, it was concluded that the scattering from the clouds dominated the global irradiance, and this scattering was relatively unaffected by the scattering off opaque clouds in the translucent atmosphere.Analysis of the translucent overcast sky UVA and UVB radiance measurements using a semi-empirical distribution model showed that the spectral influences on multiple scattering, single scattering, and horizon brightening components of the distributions agreed with basic atmospheric radiation theory. The best model used solar zenith, the sky zenith, and the scattering angle with resultant coefficient of determination values of 0.62 and 0.25 for the UVA and UVB respectively. The developed equations can be applied directly to the diffuse sky irradiance on the horizontal to provide radiance distributions for the sky.With 6 Figures     

Stable carbon isotope analysis on fossil Cedrus pollen shows summer aridification in Morocco during the last 5000 years

Quantitative climate reconstructions from pollen typically rely on empirical relationships between pollen abundances or assemblages and climate, such as the modern analogue technique. However, these techniques may be problematic when applied to fossil sequences, as they cannot separate anthropogenic from climatic influence on pollen assemblages. Here, we reconstruct Mid‐ to Late Holocene summer aridity in the Middle Atlas, Morocco, using stable carbon isotope analysis of isolated fossil Cedrus pollen. This approach is based on well‐documented plant physiological responses to moisture stress and is therefore independent of vegetation composition. We find that there has been a general long‐term trend of increasing summer aridity in the region during the last 5000 years to the present day. The gradual decline of Cedrus atlantica forest in the Late Holocene follows this aridity trend. Additionally, we show how isolating a specific pollen type for carbon isotope analysis yields a robust climate signal, versus using pollen concentrates or bulk sediment. Our findings indicate that climate has become drier in the region and confirms the Mid‐ to Late Holocene aridification trend observed more widely in the western Mediterranean, using a novel proxy for this region with good potential for wider application in other environments.     

The science process for selecting the landing site for the 2011 Mars Science Laboratory

The process of identifying the landing site for NASA’s 2011 Mars Science Laboratory (MSL) began in 2005 by defining science objectives, related to evaluating the potential habitability of a location on Mars, and engineering parameters, such as elevation, latitude, winds, and rock abundance, to determine acceptable surface and atmospheric characteristics. Nearly 60 candidate sites were considered at a series of open workshops in the years leading up to the launch. During that period, iteration between evolving engineering constraints and the relative science potential of candidate sites led to consensus on four final sites. The final site will be selected in the Spring of 2011 by NASA’s Associate Administrator for the Science Mission Directorate. This paper serves as a record of landing site selection activities related primarily to science, an inventory of the number and variety of sites proposed, and a summary of the science potential of the highest ranking sites.     

Chronology of the Lower and Middle Palaeolithic in NW Europe: developer-funded investigations at Dunbridge,Hampshire, southern England

This paper reports important findings relating to the chronology of Palaeolithic occupation, artefact typology and Quaternary fluvial deposits from a geoarchaeological watching brief undertaken over 17 years at Kimbridge Farm Quarry, Dunbridge, Hampshire. Sections were recorded and sampled and 198 artefacts, principally hand axes, were collected, with the primary aim of enhancing understanding of the geological context of the richest Lower Palaeolithic assemblage from Hampshire. Digital terrain modelling was used to characterize the three-dimensional form of the fluvial geology. Two gravel terraces have been confirmed: an upper Belbin Formation, which contained most of the archaeological artefacts, and a lower Mottisfont Formation. Results of specific note included recovery of artefacts demonstrating elements of ‘proto-Levallois’ technology from within the Belbin Gravel deposition. Fully developed Levallois technology was present across both the Belbin Gravel and the Mottisfont Formation at Dunbridge, the latter having an otherwise relatively sparse Palaeolithic content. Previously published OSL dating, supplemented by new data, has been combined with uplift modelling to suggest dates of MIS 9b and MIS 8, respectively, for these two gravels. This fits well with evidence from other sites in England and the near Continent for the timing of the earliest Levallois at around MIS 9. The results from the Dunbridge watching brief have demonstrated that this response provides a relatively cost effective method by which important scientific data can be salvaged from commercial quarrying.