The metamorphosed mafic-ultramafic complex of Mokuro, Ilesha Schist Belt, southwestern Nigeria

In the Proterozoic Schist Belt of Nigeria, lenticular bodies of metabasites and meta-ultramafics are frequently intercalated within staurolite bearing metapelitic schists. Such a metamorphosed mafic-ultramafic complex is particularly well exposed in the Mokuro riverbed between the towns of Ife and Ilesha. These outcrops display contact relationships with the surrounding metasediments, as well as between the individual mafic and ultramafic rock types. The most common mafic rocks are indistinctly layered amphibolites, accompanied by apatite rich amphibolites and massive amphibolites, in part rich in ilmenite and pyrrhotite. Among the generally massive ultramafic rocks, nearly monomineralic amphibole rocks predominate, while chlorite-amphibole, talc-chlorite-amphibole and talc bearing olivine-chlorite-amphibole rocks occur in subordinate amounts.Field, textural and geochemical evidence suggest that the mafic-ultramafic complex derived from a thick, structurally differentiated basaltic sill that contained doleritic portions in its interior. Slow cooling rates in these inner parts enabled crystal settling with the formation of ultramafic cumulates. Due to the enrichment of volatiles during the crystallisation process, higher amounts of apatite and sulphides, as well as late magmatic amphibole, were formed in parts of the mafic-ultramafic body.Mineral assemblages in the mafic-ultramafic complex testify to a metamorphic overprint under amphibolite-facies conditions. Thermodynamic modelling in the system CMFASH leads to an estimated P–T range of 1.5–3 kbar and 550–620°C for the metamorphic peak assemblage talc-olivine-chlorite-Ca amphibole-orthoamphibole.     

Variability and anisotropy of mechanical properties of the pittsburgh coal seam

SummaryVariability and Anisotropy of Mechanical Properties of the Pittsburgh Coal Seam Results of an experimental program to determine the vertical variation of material stiffness and strength of an important coal seam are presented, with the aim of providing information for realistic modeling for purposes of analysis. The seam is divided into four zones, and data from each are evaluated statistically. It is concluded that this seam contains two zones with measurably different properties, which, however, are small compared to the observed scatter of data.

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ZusammenfassungStreubereich und Anisotropie der mechanischen Eigenschaften des Pittsburgher Kohleflözes Es werden Ergebnisse eines Versuchsprogramms zur Bestimmung der senkrechten Veränderung der Steifheit und Festigkeit des Materials in einem wichtigen amerikanischen Kohlenflöz präsentiert, um Unterlagen für realistische Modellbildung zum Zwecke der Spannungsberechnung zu liefern. Der Flöz ist in vier Zonen unterteilt, deren Daten statistisch untersucht wurden. Es ergab sich, daß dieser Flöz zwei Zonen mit meßbar unterschiedlichen Eigenschaften enthält; diese Unterschiede sind aber klein im Vergleich zur Streuung der einzelnen Daten.

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RésuméVariabilité et anisotropie des propriétés mécaniques du banc de charbon de Pittsburgh On a analysé, par échantillons, la variabilité de la résistance et du module d'un banc de charbon épais, avec la profondeur. Le but de l'étude est d'obtenir des valeurs réalistes qui puissent être utilisées dans une analyse par méthodes numériques. Le banc est divisé en quatre zones, et les résultats sont analysés de façon statistique, séparément pour chaque zone. On a conclut que ce banc contient deux zones dont les propriétés mécaniques diffèrent. Cependant ces différences ne dépassent pas l'ordre de grandeur des écarts dans les observations sur chaque zone.

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With 10 Figures     

Thermal properties and coal rank in rocks and coal seams of the southern Sydney Basin,new South Wales: A palaeogeothermal explanation of coalification

Measurements of thermal conductivity on 106 disc specimens of rocks from 275 m of the Permian to Triassic section of the Southern Coalfield of the southern Sydney Basin have been carried out in an effort to explain a high rank gradient in the Permian coals. The samples came from six diamond drill holes north and west of Wollongong, although one hole only provided specimens of a syenitic sill (n = 17, mean thermal conductivity = 2.36 W/m°K, s.d. 0.03). When combined with previously published data on chip specimens, with which there is good agreement, from a further four drill holes the mean thermal conductivity for the late Permian and early Triassic sandstones and shales is 3.20 W/m°K.Heat generation by Permian volcanic rocks below the coal measures (from about 1 to 3 μW/m³), and by basement granitic rocks, appears to be consistent with previously reported heat flow for the southern Sydney Basin (about 80 mW/m²). This heat flow is a relatively high value for the east coast of Australia. Younger (Mesozoic and Tertiary) intrusive and extrusive igneous rocks produce local coal-rank anomalies, but do not appear to have any regional effect.The rank of coals above the Permian volcanic rocks appears to be little affected by the presence of the igneous rocks and the coal-rank decreases towards the major area of vulcanicity. Organic matter in sedimentary rocks interbedded with the volcanic rocks is of relatively high rank but it appears that these thermal effects do not extend more than about 100 m above the base of the coal measures. The area of high rank north and northwest of Wollongong seems likely to be a regional effect associated with a combination of high heat generation in basement and the Permian rocks, and high heat flow from the basement. Greater cover on the coal measures, together with an increase in the proportion of rocks of relatively low thermal conductivity in the cover, may also influence the rank in the Permian coal.     

A structural and geophysical approach to the study of fractured aquifers in the Scansano-Magliano in Toscana Ridge, southern Tuscany, Italy

Fresh water availability has recently become a serious concern in the Italian Apennines, as various activities rely on a predictable supply. Along the ridge between Scansano and Magliano in Toscana, in southern Tuscany, the situation is further complicated by contamination of the nearby alluvial aquifers. Aquifers locally consist of thin fractured reservoirs, generally within low-permeability formations, and it can be difficult to plan the exploitation of resources based on conventional techniques. An integrated study based on geological data investigated the link between tectonics and groundwater circulation, to better define the hydrological model. After the regional identification of fault and fracture patterns, a major structure was investigated in detail to accurately map its spatial position and to understand the geometry and properties of the associated aquifer and assess its exploitation potential. The subsurface around the fault zone was clearly imaged using ground probing radar, two-dimensional and three-dimensional resistivity tomography, and three-dimensional shallow seismic surveys. The vertical and horizontal contacts between the different geological units of the Ligurian and Tuscan series were resolved with a high degree of spatial accuracy. Three-dimensional high-resolution geophysical imaging proved to be a very effective means of characterising small-scale fractured reservoirs.     

Are We There Yet? A Roadmap to Understanding National Park Service Rulemaking

The preproposal stage of the rulemaking process is notoriously understudied, but enormously important in determining regulatory outputs. Recently, Rinfret (2011c Rinfret , S. R. 2011c . Frames of influence: U.S. environmental rulemaking case studies . Rev. Policy Res. 28 ( 3 ): 231 – 245 .[Crossref], [Web of Science ®] , [Google Scholar]) analyzed the U.S. Fish and Wildlife Service (USFWS) rulemaking process and developed a frame analysis model to interpret stakeholder influence during the preproposal stage. Rinfret argues that stakeholders use three frames to influence agency rulemaking, including an expertise, a fiscal feasibility, and an information frame. This article tests this model to determine whether it is applicable to other federal agencies such as the National Park Service (NPS). Through an analysis of stakeholder framing within the 2012 NPS Yellowstone Winter Use Rule, this research confirms that Rinfret's model is indeed applicable to the NPS process. Therefore, this research suggests that this theoretical model examining stakeholder influence is applicable to other public land agencies, and arguably can be applied across the bureaucracy.     

The response of the South Asian Summer Monsoon circulation to intensified irrigation in global climate model simulations

Agricultural intensification in South Asia has resulted in the expansion and intensification of surface irrigation over the twentieth century. The resulting changes to the surface energy balance could affect the temperature contrasts between the South Asian land surface and the equatorial Indian Ocean, potentially altering the South Asian Summer Monsoon (SASM) circulation. Prior studies have noted apparent declines in the monsoon intensity over the twentieth century and have focused on how altered surface energy balances impact the SASM rainfall distribution. Here, we use the coupled Goddard Institute for Space Studies ModelE-R general circulation model to investigate the impact of intensifying irrigation on the large-scale SASM circulation over the twentieth century, including how the effect of irrigation compares to the impact of increasing greenhouse gas (GHG) forcing. We force our simulations with time-varying, historical estimates of irrigation, both alone and with twentieth century GHGs and other forcings. In the irrigation only experiment, irrigation rates correlate strongly with lower and upper level temperature contrasts between the Indian sub-continent and the Indian Ocean (Pearson’s r = ?0.66 and r = ?0.46, respectively), important quantities that control the strength of the SASM circulation. When GHG forcing is included, these correlations strengthen: r = ?0.72 and r = ?0.47 for lower and upper level temperature contrasts, respectively. Under irrigated conditions, the mean SASM intensity in the model decreases only slightly and insignificantly. However, in the simulation with irrigation and GHG forcing, inter-annual variability of the SASM circulation decreases by ~40 %, consistent with trends in the reanalysis products. This suggests that the inclusion of irrigation may be necessary to accurately simulate the historical trends and variability of the SASM system over the last 50 years. These findings suggest that intensifying irrigation, in concert with increased GHG forcing, is capable of reducing the variability of the simulated SASM circulation and altering the regional moisture transport by limiting the surface warming and reducing land–sea temperature gradients.     

Identifying hot spots of security vulnerability associated with climate change in Africa

Given its high dependence on rainfed agriculture and its comparatively low adaptive capacity, Africa is frequently invoked as especially vulnerable to climate change. Within Africa, there is likely to be considerable variation in vulnerability to climate change both between and within countries. This paper seeks to advance the agenda of identifying the hot spots of what we term “climate security” vulnerability, areas where the confluence of vulnerabilities could put large numbers of people at risk of death from climate-related hazards. This article blends the expertise of social scientists and climate scientists. It builds on a model of composite vulnerability that incorporates four “baskets” or processes that are thought to contribute to vulnerability including: (1) physical exposure, (2) population density, (3) household and community resilience, and (4) governance and political violence. Whereas previous iterations of the model relied on historical physical exposure data of natural hazards, this paper uses results from regional model simulations of African climate in the late 20th century and mid-21st century to develop measures of extreme weather events—dry days, heat wave events, and heavy rainfall days—coupled with an indicator of low-lying coastal elevation. For the late 20th century, this mapping process reveals the most vulnerable areas are concentrated in Chad, the Democratic Republic of the Congo, Niger, Somalia, Sudan, and South Sudan, with pockets in Burkina Faso, Ethiopia, Guinea, Mauritania, and Sierra Leone. The mid 21st century projection shows more extensive vulnerability throughout the Sahel, including Burkina Faso, Chad, Mali, northern Nigeria, Niger, and across Sudan.