Holocene coastal environmental changes on the periphery of an area of glacio‐isostatic uplift: an example from Scapa Bay,Orkney, UK

The first detailed investigation of a deep, coastal, sedimentary basin in Orkney reveals a complex Holocene history of back‐barrier morphodynamics. At Scapa Bay, the sea flooded a freshwater marsh after ca. 9400 yr BP at ca. ?5.4 m OD. Before ca. 7800 BP, abundant sediment from nearby cliffs was mobilised inland into a series of gravel barriers across the valley mouth. By ca. 7500 BP, direct marine influence was restricted in the back‐barrier area, although saltmarsh persisted until ca. 5900 BP. By then, at least four gravel ridges had enclosed the backing lagoon, where freshwater inputs became dominant. As terrestrial sediments filled the basin, another freshwater marsh developed. The multiple barrier complex demonstrates progradation resulting from continuous sediment supply in a sheltered embayment. The progressively rising height of the barrier crests seawards probably resulted from a combination of factors such as barrier morphodynamics, increased storminess and long‐term rising relative sea levels. The dominant vegetation surrounding Scapa Bay changed from open grassland to scrub ca. 9400 BP, then to deciduous woodland ca. 7800 BP, and to dwarf‐shrub heath ca. 2600 BP, the latter probably a response to a combination of climate change and human activity. Copyright © 2007 John Wiley & Sons, Ltd.     

Paleoenvironmental reconstruction in the western lacustrine plain of Llancanelo Lake,Mendoza, Argentina

Lakes are key sites for studying paleoclimates. Llancanelo Lake (southern Mendoza Province, western Argentina) is an endoreic, highly saline water body located in the southern extreme of a tectonic basin, the Central or Huarpes Depression. The lake is located between the Andean Cordillera, San Rafael Block and Payenia Volcanic Field. The lake evolved as a major regional depocenter during the Pliocene-Quaternary, hence it contains important thicknesses of intra and extra basinal clastic and evaporitic sediments mainly dominated by volcaniclastic products. The main conditioning factors in the lake evolution were arc and back-arc volcanism as well as climatic changes. Geomorphological and sedimentary evidence supports the hypothesis that the lake was in past times larger than in present days. This paper estimates the lake’s former extension on the western lacustrine plain using electromagnetic induction (EMI) and geoelectricity (Multielectrode Resistivity Meter) surveys, as well as shallow wells, along an 8 km long transect perpendicular to the lake’s western shoreline. The geophysical and sedimentological information, as well as microfaunal studies, lab analysis and petrographic/EDAX determinations, support the presence, in the subsoil, of a lacustrine sequence at least 30 m thick composed mainly of volcaniclastic sediments. Volcanic eruptions and climatic changes influenced the evolution of the lake, producing intercalations in the lacustrine sedimentary sequences of ash layers, evaporites, soils, and eolian and swamp deposits.     

The globular clusters–stellar haloes connection in early-type galaxies

This paper explores if, and to what an extent, the stellar populations of early-type galaxies can be traced through the colour distribution of their globular cluster (GC) systems. The analysis, based on a galaxy sample from the Virgo Advanced Camera for Surveys data, is an extension of a previous approach that has been successful in the cases of the giant ellipticals NGC 1399 and NGC 4486, and assumes that the two dominant GC populations form along diffuse stellar populations sharing the cluster chemical abundances and spatial distributions. The results show that (a) integrated galaxy colours can be matched to within the photometric uncertainties and are consistent with a narrow range of ages; (b) the inferred mass to luminosity ratios and stellar masses are within the range of values available in the literature; (c) most GC systems occupy a thick plane in the volume space defined by the cluster formation efficiency, total stellar mass and projected surface mass density. The formation efficiency parameter of the red clusters shows a dependency with projected stellar mass density that is absent for the blue globulars. In turn, the brightest galaxies appear clearly detached from that plane as a possible consequence of major past mergers; (d) the stellar mass–metallicity relation is relatively shallow but shows a slope change at   M _*≈ 10¹⁰ M_⊙  . Galaxies with smaller stellar masses show predominantly unimodal GC colour distributions. This result may indicate that less massive galaxies are not able to retain chemically enriched interstellar matter.     

Numerical estimation of carbonate rock properties using multiscale images

Characterizing the pore space of rock samples using three‐dimensional (3D) X‐ray computed tomography images is a crucial step in digital rock physics. Indeed, the quality of the pore network extracted has a high impact on the prediction of rock properties such as porosity, permeability and elastic moduli. In carbonate rocks, it is usually very difficult to find a single image resolution which fully captures the sample pore network because of the heterogeneities existing at different scales. Hence, to overcome this limitation a multiscale analysis of the pore space may be needed. In this paper, we present a method to estimate porosity and elastic properties of clean carbonate (without clay content) samples from 3D X‐ray microtomography images at multiple resolutions. We perform a three‐phase segmentation to separate grains, pores and unresolved porous phase using 19 μm resolution images of each core plug. Then, we use images with higher resolution (between 0.3 and 2 μm) of microplugs extracted from the core plug samples. These subsets of images are assumed to be representative of the unresolved phase. We estimate the porosity and elastic properties of each sample by extrapolating the microplug properties to the whole unresolved phase. In addition, we compute the absolute permeability using the lattice Boltzmann method on the microplug images due to the low resolution of the core plug images. In order to validate the results of the numerical simulations, we compare our results with available laboratory measurements at the core plug scale. Porosity average simulations for the eight samples agree within 13%. Permeability numerical predictions provide realistic values in the range of experimental data but with a higher relative error. Finally, elastic moduli show the highest disagreements, with simulation error values exceeding 150% for three samples.     

Accuracy assessment of the Mexican National Forest Inventory map: A study in four ecogeographical areas

The accuracy of the Mexican National Forest Inventory (NFI) map is derived in four distinct ecogeographical areas, using an assessment design tailored for the project. A main achievement of the design was to integrate the high diversity of classes encompassed at the most detailed subcommunity level of the classification scheme within a cost‐controlled statistically sound assessment. A hybrid double sampling strategy was applied to the 2.5 million‐ha study area. A total of 5955 reference sites were verified against their NFI map label. The availability of detailed quasi‐synchronous reference data for the 2000 Landsat‐derived NFI and the high diversity of mapped classes allowed a careful thematic analysis on the selected regions, relevant for national extrapolation. Global accuracy estimates of 64–78 per cent were registered among the four ecogeographical areas (two with mainly temperate climate and the other two with mainly tropical climate), with the lower accuracy levels found in areas more densely covered with forests. According to the estimates, the NFI map tends to underestimate the presence of temperate forest (especially oak) and overestimate the presence of tropical forest in the areas investigated. The analysis of confusions reveals difficulties in unambiguously interpreting or labelling forests with secondary vegetation, herbaceous and/or shrub‐like vegetation as well as distinguishing between aquatic vegetation types. The design proved useful from the perspective of accuracy assessments of regional maps in biodiverse regions.     

The effects of air transportation on the movement of labor

The effects of the deregulation of airlines markets and the new technologies that have been introduced into air transportation have been heavily studied. Much of this analysis has been on the impacts on the industry and the immediate welfare implications for passengers and, to a lesser extent, cargo consignors. This study looks at the longer-term effects of the modern air transportation system on labor markets and labor migration. The growth of the service sector, the emergence of more flexible manufacturing techniques, the reduction in trade-barriers, and the creation of more sophisticated financial markets have led to greater mobility in production and in capital movement. This has been explored to some extent. Labor is, however, also more mobile - for example, since the admission of Poland to the European Union some 465,000 Polish workers have joined the UK labor market. Air transportation facilitates easier migration, makes short-term, long-distance migration viable, and allows migrants to maintain contact with their home country. Within larger countries, such as the US, there has also been a growth in long distance “week-day” migration as spouses work in different parts of the country to be reunited at weekends. The study makes use of aggregate data to look at trends in international labor movements particularly concerning the European situation, and, to a lesser extent, at recent developments within the US. It is concerned both with what is going on in terms of the use being made of air transportation by migrants and the light that this may shed on migration theory.

Retention of heavy metal ions in bentonites from Grau Region (Northern Peru)

Experimental studies on the retention of metals (Cu, Co, Ni, and Zn) in bentonite samples from the Grau Region (Northern Peru) have been accomplished using monometallic, bimetallic, trimetallic, and tetrametallic solutions. Parameters such as pH and concentration of dissolved metals and organic compounds have been evaluated by means of batch adsorption experiments. Adsorption rates indicate the suitability of these bentonites in the environmental industry for heavy metals retention purposes. In addition to its quality as physical barrier to avoid the dispersion through the environment of polluted leachates, bentonite, due to its high cation exchange capacity, can act also as a chemical barrier, protecting the quality of surface and groundwater systems, while limiting the migration of heavy metals in solid residues or sludge stocked in security landfills. Adsorption rates of tested bentonites were proved to decrease when concentrations of both metal and organic compounds, as well as the number of ionic species, increase in solution; additionally, lower metal removal rates from solution were obtained when extremely acidic conditions were achieved.     

Changes in growing season in the Northeastern United States

ABSTRACT

Changes in growing season length (GSL) are of concern for agricultural, phenological, economic, epidemiological, and bioclimatological reasons. This research identifies spatial and temporal changes over the last several decades in GSL, along with the day-of-year of the last spring freeze and first autumn freeze, for the northeastern United States – a region particularly susceptible to such changes due to the large population and intense economic activities. Results suggest that growing season has significantly increased in length since 1980 as compared to prior to 1980, and both spatial and temporal variation in GSL has decreased for the region over time. Changes to GSL for this region are driven more by a shift in the first autumn freeze date than the last spring freeze date. The areas of greatest increase in GSL in the pre- vs. post-1980 period tend to be in the high elevations, near large water bodies, and near the largest cities. Results will assist environmental planners as they prepare mitigation and adaptation strategies amid a changing environment.