Bedrock controls on the mineralogy and chemistry of PM<Subscript>10</Subscript> extracted from Australian desert sediments

Given the relevance of desert aerosols to environmental issues such as dust storms, climate change and human health effects, we provide a demonstration of how the bedrock geology of an arid area influences the mineralogy and geochemistry of even the finest particulate matter (i.e., the inhalable fraction <10 μm in size: PM₁₀). PM₁₀ samples extracted from desert sediments at geologically contrasting off-road sites in central and southeastern Australia (granitic, high grade metamorphic, quartzitic sandstone) were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The “granitic” PM₁₀ are highly alkali feldspathic and illitic, with a wide range of accessory minerals including rutile (TiO₂), monazite [(Ce, La, Nd, Th, Y) PO₄], xenotime (YPO₄), apatite [Ca₅(PO₄)₃ (F, OH, Cl)], hematite (Fe₃O₄), zircon (ZrSiO₄) and thorite (ThSiO₄). This mineralogy is reflected in the geochemistry which shows notable enrichments in rare earth elements (REE) and most high field strength elements (both held in the accessory minerals), and higher than normal levels of low (<2.0) ionic potential elements (Na, K, Li, Cs, Rb: held in alkali feldspar and illite). The “metamorphic” resuspended PM₁₀ define a mineralogy clearly influenced by local exposures of pelitic and calc-silicate schists (sillimanite, muscovite, calcite, Ca-amphibole), a dominance of monazite over other REE-bearing phases, and a geochemistry distinguished by enrichments in alkaline earth metals (Ca, Mg, Ba, Sr) and depletion in heavy REE. The “quartzite” PM₁₀, derived from rocks already recycled by Precambrian erosion and sedimentary transport, show a sedimentologically mature mineralogy of mostly quartz and kaolinite, detrital accessory ilmenite, rutile, monazite and hematite, and the strongest geochemical depletion (especially K, Rb, Cs, Na, Ca, Mg, Ba).     

Together,but separate: neighborhood-scale patterns and correlates of spatial segregation between male and female same-sex couples in Melbourne and Sydney

Considerable research has examined the relationships between queer communities and the city, particularly within a qualitative, North American context. This paper provides the first quantitative treatment of the spatial patterning of male and female same-sex couples in Australia’s two largest urban centers, examining differences between the two groups and their potential drivers. Male and female same-sex couples are shown to concentrate in distinct regions of Melbourne and Sydney that are segregated from each other, but nonetheless geographically close: together, but separate. Spatial regression analyses provided an incomplete explanation of these patterns. A number of factors were identified, endogenous and exogenous to the same-sex couple community, which provide a potential explanatory framework for explaining the aggregation of these groups. Very little emerges from this analysis which explains segregation for these groups. The ultimate etiology of segregation between male and female same-sex couples in Melbourne and Sydney remains elusive.     

Future evolution of a tidal inlet due to changes in wave climate, Sea level and lagoon morphology (Óbidos lagoon, Portugal)

Tidal inlets are extremely dynamic, as a result of an often delicate balance between the effects of tides, waves and other forcings. Since the morphology of these inlets can affect navigation, water quality and ecosystem dynamics, there is a clear need to anticipate their evolution in order to promote adequate management decisions. Over decadal time scales, the position and size of tidal inlets are expected to evolve with the conditions that affect them, for instance as a result of climate change. A process-based morphodynamic modeling system is validated and used to analyze the effects of sea level rise, an expected shift in the wave direction and the reduction of the upper lagoon surface area by sedimentation on a small tidal inlet (Óbidos lagoon, Portugal). A new approach to define yearly wave regimes is first developed, which includes a seasonal behavior, random inter-annual variability and the possibility to extrapolate trends. Once validated, this approach is used to produce yearly time series of wave spectra for the present and for the end of the 21st century, considering the local rotation trends computed using hindcast results for the past 57 years. Predictions of the mean sea level for 2100 are based on previous studies, while the bathymetry of the upper lagoon for the same year is obtained by extrapolation of past trends. Results show, and data confirm, that the Óbidos lagoon inlet has three stable configurations, largely determined by the inter-annual variations in the wave characteristics. Both sea level rise and the reduction of the lagoon surface area will promote the accretion of the inlet. In contrast, the predicted rotation of the wave regime, within foreseeable limits, will have a negligible impact on the inlet morphology.     

The application of GPR and ERI in combination with exposure logging and retrodeformation analysis to characterize sinkholes and reconstruct their impact on fluvial sedimentation

This work illustrates the practicality of investigating sinkholes integrating data gathered by ground penetrating radar (GPR), electrical resistivity imaging (ERI) and trenching or direct logging of the subsidence‐affected sediments in combination with retrodeformation analysis. This mutidisciplinary approach has been tested in a large paleosinkhole developed during the deposition of a Quaternary terrace on salt‐bearing evaporites. The subsidence structure, exposed in an artificial excavation, is located next to Puilatos, a village that was abandoned in the 1970s due to severe subsidence damage. Detailed logging of the exposure revealed that the subsidence structure corresponds to an asymmetric sagging and collapse paleosinkhole with no clear evidence of recent activity. The sedimentological and structural relationships together with the retrodeformation analysis indicate that synsedimentary subsidence controlled channel location, the development of a palustrine environment and local changes in the channel pattern. GPR profiles were acquired using an array of systems with different antenna frequencies, including some recently developed shielded antennas with improved vertical resolution and penetration depth. Although radargrams imaged the faulted sagging structure and provided valuable data on fault throw, they did not satisfactorily image the complex architecture of the fluvial deposit. ERI showed lower resolution but higher penetration depth when compared to GPR, roughly capturing the subsidence structure and yielding information on the thickness of the high‐resistivity alluvium and the nature of the underlying low‐resistivity karstic residue developed on top of the halite‐bearing evaporitic bedrock. Data comparison allows the assessment of the advantages and limitations of these complementary techniques, highly useful for site‐specific sinkhole risk management. Copyright © 2016 John Wiley & Sons, Ltd.     

Lateral variations of attenuation coefficients, group and phase velocities of rayleigh waves in Europe

Rayleigh wave group and phase velocities and attenuation coefficients are investigated in the 15–60-s period range for earthquakes occurring in the European area and registered at European stations. Observed group and phase velocities show clear differences in the period range 20–40 s, whereas attenuation coefficients are differentiated from 45 s to larger periods. From the shape of dispersion and attenuation curves, two broad zones have been isolated and designated as Western Europe and Southeastern Europe. Although some scatter is present, specially for attenuation, the data suggest that in general the shear velocity and Q_β values are higher for Southeastern Europe than for Western Europe. For Southeastern Europe there is a channel of low velocity and low Q_β, apparently correlated, located at the lower crust: in both regions there is a channel of low velocity and low Q_β values located at the uppermost mantle. In each case there also exists a channel of high Q_β values located at the lower crust but at slightly different depths.     

Relicts of an intra-oceanic arc in the Sapi-Shergol mélange zone (Ladakh, NW Himalaya, India): implications for the closure of the Neo-Tethys Ocean

In the Ladakh–Zanskar area, relicts of both ophiolites and paleo-accretionary prism have been preserved in the Sapi-Shergol mélange zone. The paleo-accretionary prism, related to the northward subduction of the northern Neo-Tethys beneath the Ladakh Asian margin, mainly consists of tectonic intercalations of sedimentary and blueschist facies rocks. Whole rock chemical composition data provide new constraints on the origin of both the ophiolitic and the blueschist facies rocks. The ophiolitic rocks are interpreted as relicts of the south Ladakh intra-oceanic arc that were incorporated in the accretionary prism during imbrication of the arc. The blueschist facies rocks were previously interpreted as oceanic island basalts (OIB), but our new data suggest that the protolith of some of the blueschists is a calc-alkaline igneous rock that formed in an arc environment. These blueschists most likely originated from the south Ladakh intra-oceanic arc. This arc was accreted to the southern margin of Asia during the Late Cretaceous and the buried portion was metamorphosed under blueschist facies conditions. Following oceanic subduction, the external part of the arc was obducted to form the south Ladakh ophiolites or was incorporated into the Sapi-Shergol mélange zone. The incorporation of the south Ladakh arc into the accretionary prism implies that the complete closure of the Neo-Tethys likely occurred by Eocene time.     

Stock Evaluation of Three Littoral Echinoid Species on the Catalan Coast North-Western Mediterranean

Abstract. We estimated the abundances of the three common littoral echinoid species Paracentrotus lividus, Arbacia lixula and Sphaerechinus granularis in a littoral zone between 0 and 10m depth on the Catalan shores NE Spain. Densities of each species were estimated from a total number of 11 571× 1 m² sampling units deployed at 152 sites along the 13 zones into which the coast was divided. The surface area available in each of these zones was estimated at the scale of the sampling unit 1 m² taking into account the fractal dimension of the shore. The stocks individuals > 2cm test diameter of these species for the whole Catalan shore ≅ 300 km, straight-line distance were estimated to be about 279.1 × 10⁶ individuals for P. lividus , 28.9 × 10⁶ individuals for A. lixula and 10.9 × 10⁶ individuals for S. granularis. These sea-urchins are key species in the regulation of algal communities and some of them P. lividus. S. granularis are of commercial interest. This information will provide a tool for the future monitoring and management of this resource, which now faces diverse pressures of human origin.     

DuneXpress

The DuneXpress observatory will characterize interstellar and interplanetary dust in-situ, in order to provide crucial information not achievable with remote sensing astronomical methods. Galactic interstellar dust constitutes the solid phase of matter from which stars and planetary systems form. Interplanetary dust, from comets and asteroids, represents remnant material from bodies at different stages of early solar system evolution. Thus, studies of interstellar and interplanetary dust with DuneXpress in Earth orbit will provide a comparison between the composition of the interstellar medium and primitive planetary objects. Hence DuneXpress will provide insights into the physical conditions during planetary system formation. This comparison of interstellar and interplanetary dust addresses directly themes of highest priority in astrophysics and solar system science, which are described in ESA’s Cosmic Vision. The discoveries of interstellar dust in the outer and inner solar system during the last decade suggest an innovative approach to the characterization of cosmic dust. DuneXpress establishes the next logical step beyond NASA’s Stardust mission, with four major advancements in cosmic dust research: (1) analysis of the elemental and isotopic composition of individual interstellar grains passing through the solar system, (2) determination of the size distribution of interstellar dust at 1 AU from 10^− 14 to 10^− 9 g, (3) characterization of the interstellar dust flow through the planetary system, (4) establish the interrelation of interplanetary dust with comets and asteroids. Additionally, in supporting the dust science objectives, DuneXpress will characterize dust charging in the solar wind and in the Earth’s magnetotail. The science payload consists of two dust telescopes of a total of 0.1 m² sensitive area, three dust cameras totaling 0.4 m² sensitive area, and a nano-dust detector. The dust telescopes measure high-resolution mass spectra of both positive and negative ions released upon impact of dust particles. The dust cameras employ different detection methods and are optimized for (1) large area impact detection and trajectory analysis of submicron sized and larger dust grains, (2) the determination of physical properties, such as flux, mass, speed, and electrical charge. A nano-dust detector searches for nanometer-sized dust particles in interplanetary space. A plasma monitor supports the dust charge measurements, thereby, providing additional information on the dust particles. About 1,000 grains are expected to be recorded by this payload every year, with 20% of these grains providing elemental composition. During the mission submicron to micron-sized interstellar grains are expected to be recorded in statistically significant numbers. DuneXpress will open a new window to dusty universe that will provide unprecedented information on cosmic dust and on the objects from which it is derived.