High-resolution analysis of submarine lobes deposits: Seismic-scale outcrops of the Lauzanier area (SE Alps, France)

The Lauzanier area represents the northernmost extension of the Annot Sandstone series and contains deposits between 650 and 900 m-thick. This basin was active from upper Bartonian or lower Priabonian to early Rupelian. It is composed of two superposed units separated by a major unconformity. The sediment supply is due to channelled flows coming from the south. Flow processes include mass flow to turbidity currents. The size of the particles and the absence of fine-grained sediment suggest a transport over a short distance. The Lower Unit is made of coarse-grained tabular beds interpreted as non-channelled lobe deposits. The Upper Unit is made of massive conglomerates interpreted as the channelled part of lobes. These lobe deposits settle in a tectonically confined basin according to topographic compensation that occurs from bed scale to unit scale. The abrupt progradation between the lower and the upper unit seems related to a major tectonic uplift in the area. This uplift is also suggested by a change in the petrographic nature of the source and an abrupt coarsening of the transported clasts.This field example allows providing high resolution analysis for depositional sedimentary sequences of terminal lobe deposits in a coarse-grained turbidite system. The outcrop analysis shows the lateral evolution of deposits and the system progradation allows a longitudinal analysis of facies evolution by superposing on the same outcrops the channelled lobe system and the non-channelled lobe system. These results of high-resolution outcrop analysis can be extrapolated to results obtained on sedimentary lobes in recent deep-sea turbidite system that are either restricted to cores, or with a lesser resolution (seismic).     

Contrasting stratified plutons exposed in tilt blocks, Eldorado Mountains, Colorado River Rift, NV, USA

Roof-to-floor exposures of mid-Miocene plutons in tilt blocks south of Las Vegas, NV, reveal distinct but strongly contrasting magma chamber statigraphy. The Searchlight and Aztec Wash plutons are well-exposed, stratified intrusions that show a similar broad range in composition from 45–75 wt.% SiO₂. Homogeneous granites that comprise about one-third of each intrusion are virtually identical in texture and elemental and isotopic chemistry. Mafic rocks that are present in both plutons document basaltic input into felsic magma chambers. Isotopic compositions suggest that mafic magmas were derived from enriched lithospheric mantle with minor crustal contamination, whereas more felsic rocks are hybrids that are either juvenile basaltic magma+crustal melt mixtures or products of anatexis of ancient crust+young (Mesozoic or Miocene?) mafic intraplate.

Despite general similarities, the two plutons differ markedly in dimensions and lithologic stratigraphy. The Searchlight pluton is much thicker (10 vs. 3 km) and has thick quartz monzonite zones at its roof and floor that are absent in the Aztec Wash pluton. Isotopic and elemental data from Searchlight pluton suggest that the upper and lower zones are cogenetic with the granite; we interpret the finer grained, slightly more felsic upper zone to represent a downward migrating solidification front and the lower zone to be cumulate. In contrast, the upper part of the Aztec Wash pluton is granite, and a heterogeneous, mafic-rich injection zone with distinct isotopic chemistry forms the lower two-thirds of the intrusion. Similar mafic rocks are relatively sparse in Searchlight pluton and do not appear to have played a central role in construction of the pluton. Large felsic and composite dikes that attest to repeated recharging and intrachamber magma transfer are common in the Aztec Wash pluton but absent in the Searchlight pluton. Thus, although both intrusions were filled by similar magmas and both developed internal stratification, the two intrusions evolved very differently. The distinctions may be attributable to scale and resulting longevity and/or to subtle differences in tectonic setting.     

Transnational elites in global cities: British expatriates in Singapore's financial district

Skilled international migration is as an important process of both contemporary globalization and the global city. The establishment of a transnational elite of expatriate labour in international finance plays a vital part in the accumulation of capital within international financial centres (IFCs). Expatriate labour has become a major determinant of the IFC, creating financial capital through complex social relations, knowledge networks, practices and discourses. The principal argument being made in this paper is that expatriates are major agents in the accumulation and transfer of financial knowledge in the IFC, and that such processes are undertaken through expatriate global–local knowledge networks and other social practices. The paper is divided into three major parts. Following a discussion of transnational elites as expatriates in global cities, which also conceptualises their contribution to the spatialization of financial knowledge networks, the empirical study investigates the working, social and cultural knowledge networks and practices of British expatriates in Singapore. Finally, the paper revisits the conceptual work on transnational elites and suggests that expatriates were deeply embedded in global–local relations in the workplace and the business/social sphere through interaction with local ‘western educated/experienced' Singaporeans, but were disembedded from the local in the home and other household social spaces due to the invisibility of the local population in their interactions. Both the theoretical and empirical analyses suggests that expatriates are flow in the Castellian spatial logic of the network society.     

Modelling water-table depth in a primary aquifer to identify potential wetland hydrogeomorphic settings on the northern Maputaland Coastal Plain,KwaZulu-Natal,South Africa

The primary aquifer on the Maputaland Coastal Plain in northern KwaZulu-Natal, South Africa, is the principal source of water for rivers, lakes and most of the wetlands in dry periods, and is recharged by these systems in wet periods. Modelling hydrologic conditions that control regional water-table depth can provide insight into the spatial patterns of wetland occurrence and of the persistence of wet conditions that control their character. This project used a groundwater model (MODFLOW) to simulate 10-year water-table fluctuations on the Maputaland Coastal Plain from January 2000 to December 2010, to contrast the conditions between wet and dry years. Remote sensing imagery was used to map “permanent” and “temporary” wetlands in dry and wet years to evaluate the effectiveness of identifying the suitable conditions for their formation using numerical modelling techniques. The results confirm that topography plays an important role on a sub-regional and local level to support wetland formation. The wetlands’ extent and distribution are directly associated with the spatial and temporal variations of the water table in relation to the topographical profile. Groundwater discharge zones in the lowland (1–50 masl) areas support more permanent wetlands with dominantly peat or high organic soil substrates, including swamp forest and most of the permanent open water areas. Most temporary wetlands associated with low-percentage clay occurrence are through-flow low-lying interdune systems characterised by regional fluctuation of the water table, while other temporary wetlands are perched or partially perched. The latter requires a more sophisticated saturated-unsaturated modelling approach.     

Landslide risk perception: a case study in Southern Italy

Perceptions of risk are a key issue when seeking to develop systems, practices and policies to protect local populations. This is particularly evident when risk mitigation strategies involve non-structural measures such as relocation and warning systems which presuppose the active involvement of the communities in question. This study adopts an interdisciplinary approach to studying the perceptions, knowledge and opinions on landslide risk amongst residents in Sarno, a small town in Southern Italy which was hit by disastrous landslides on 5–6 May 1998. The paper presents the results of a survey conducted in the months of March, April and May 2013 using a purpose-designed questionnaire. The survey was conducted using face-to-face interviews with 100 residents, 60 of whom live inside the so-called “red zone”, a territory declared at high residual risk soon after the events of 1998. The questionnaire included questions relating to perceived risk exposure, trust in institutions responsible for risk management, evaluations of risk mitigation measures and the early-warning strategy. The results of the study clearly emerges, amongst other issues, that the organisms which are responsible for risk management in Sarno need to develop more effective communication strategies in order to transmit knowledge about the actions implemented to reduce landslide risk in the area.     

Alteration of fluid properties during the initial operation of a geothermal plant: results from in situ measurements in Groß Schönebeck

Recently, the thermal fluid loop has been established and continuosly operated for 7 days at the geothermal in situ laboratory in Groß Schönebeck (North German Basin). During this initial phase of fluid production, the fluid temperature, measured at the surface, continuously increased until a stable value of about 98 °C was established. Fluid physicochemical properties (pH, redox, density, temperature, and pressure) were measured online and in situ with a newly developed fluid monitoring system (FluMo). Additionally, fluid samples have been collected at various temperatures (in 5–10 °C steps) directly at the production well at about 10 bar pressure. From the pressurized sampling tool, the fluid was directly transferred into a heated autoclave, which allowed filtration (0.2 μm) in the absence of oxygen. Physicochemical parameters [pH, redox, electric conductivity, total dissolved solids (TDS)] as well as acid capacity (K _S 4.3) of these samples have been measured onsite at atmospheric conditions. Concentrations of anions, total organic carbon, and metals were analyzed later in the laboratory. Both, measurements in collected samples or in situ (FluMo) analysis of most the parameters density, electric conductivity, or TDS indicated relatively constant values over the whole production time (1.17–1.18 g · cm^?3, 215–221 mS · cm^?1, 241–260 g · L^?1, respectively). Good correlation was also found for pH values (pH = 6.6–6.9), whereas the redox values varied between ?1 and 46 mV when determined at 25 °C and decreased strongly when measured in situ with increasing temperature (?110 mV at 90 °C). The elemental composition of collected samples remained also relatively constant for most compounds and was clearly higher as compared with samples collected in 2011. Results of this study demonstrate that realistic, comprehensive, and time-resolved physicochemical data can be obtained by FluMo. These detailed data sets can be crucial to understand the complex geochemical processes in a thermal water loop and eventually to take required measures on time.     

Volatiles contents, degassing and crystallisation of intermediate magmas at Volcan de Colima, Mexico, inferred from melt inclusions

In volatile-saturated magmas, degassing and crystallisation are interrelated processes which influence the eruption style. Melt inclusions provide critical information on volatile and melt evolution, but this information can be compromised significantly by post-entrapment modification of the inclusions. We assess the reliability and significance of pyroxene-hosted melt inclusion analyses to document the volatile contents (particularly H₂O) and evolution of intermediate arc magmas at Volcán de Colima, Mexico. The melt inclusions have maximal H₂O contents (≤4 wt%) consistent with petrological estimates and the constraint that the magmas crystallised outside the amphibole stability field, demonstrating that pyroxene-hosted melt inclusions can preserve H₂O contents close to their entrapment values even in effusive eruptions with low effusion rates (0.6 m³ s^?1). The absence of noticeable H₂O loss in some of the inclusions requires post-entrapment diffusion coefficients (≤1 × 10^?13 m² s^?1) at least several order of magnitude smaller than experimentally determined H⁺ diffusion coefficient in pyroxenes. The H₂O content distribution is, however, not uniform, and several peaks in the data, interpreted to result from diffusive H₂O reequilibration, are observed around 1 and 0.2 wt%. H₂O diffusive loss is also consistent with the manifest lack of correlations between H₂O and CO₂ or S contents. The absence of textural evidence supporting post-entrapment H₂O loss suggests that diffusion most likely occurred via melt channels prior to sealing of the inclusions, rather than through the host crystals. Good correlation between the melt inclusion sealing and volcano-tectonic seismic swarm depths further indicate that, taken as a whole, the melt inclusion population accurately records the pre-eruptive conditions of the magmatic system. Our data demonstrate that H₂O diffusive loss is a second-order process and that pyroxene-hosted melt inclusions can effectively record the volatile contents and decompression-induced crystallisation paths of vapour-saturated magmas.     

Sedimentary signatures of cyclic growth and destruction of stratovolcanoes: A case study from Mt. Taranaki, New Zealand

The long-term behaviour of andesite stratovolcanoes is characterised by a repetition of edifice growth phases followed by collapse. This cyclic pattern represents a natural frequency at varying timescales in the growth dynamics of stratovolcanoes worldwide. Around the > 130 ka Mt. Taranaki (Egmont volcano), New Zealand, coastal–cliff successions at 20–40 km distance comprise repeating packages of lithologically and sedimentologically distinctive mass-flow deposits. Varying depositional mechanisms and source properties of these units record growth and collapse cycles of the central edifice. These are used to construct a model for cyclic volcaniclastic sedimentation in the surrounds of stratovolcanoes. During edifice-construction phases, thick packages of tabular, predominantly monolithologic, hyperconcentrated-flow and debris-flow deposits accumulate with intercalated tephra beds. The mass-flow units commonly contain large proportions of fresh pumice or juvenile-lithic andesite. Intervals of quiescence separating eruptive periods are characterised by landscape re-adjustment, accompanied by deposition of fluvial and aeolian sediments, along with steady accretion of medial ash. In contrast, brief episodes of destruction are marked by wide-spread, distinctively clay-rich, polylithologic debris-avalanche deposits and related marginal debris flow units. The growth stages can be terminated by an eruption-triggered sector collapse, or by external forces once the edifice exceeds a critical stable height or profile (dependent on eruptive style and local geo-tectonic conditions). Once the edifice becomes metastable, regional tectonic earthquakes or shallow-level intrusion events are likely triggers for collapse. Although the resulting debris avalanches represent the greatest individual hazard from such andesite stratovolcanoes, their frequency is relatively low compared with other types of mass-flows generated during edifice-growth phases. Accurate forecasts of future hazard from mass-flow events are therefore dependent on recognition of both the frequency of a stratovolcano's growth cycle and its current position in that cycle.