Central Mediterranean tephrochronology between 313 and 366 ka: New insights from the Fucino palaeolake sediment succession

Thirty-two tephra layers were identified in the time-interval 313–366 ka (Marine Isotope Stages 9–10) of the Quaternary lacustrine succession of the Fucino Basin, central Italy. Twenty-seven of these tephra layers yielded suitable geochemical material to explore their volcanic origins. Investigations also included the acquisition of geochemical data of some relevant, chronologically compatible proximal units from Italian volcanoes. The record contains tephra from some well-known eruptions and eruptive sequences of Roman and Roccamonfina volcanoes, such as the Magliano Romano Plinian Fall, the Orvieto–Bagnoregio Ignimbrite, the Lower White Trachytic Tuff and the Brown Leucitic Tuff. In addition, the record documents eruptions currently undescribed in proximal (i.e. near-vent) sections, suggesting a more complex history of the major eruptions of the Colli Albani, Sabatini, Vulsini and Roccamonfina volcanoes between 313 and 366 ka. Six of the investigated tephra layers were directly dated by single-crystal-fusion ⁴⁰Ar/³⁹Ar dating, providing the basis for a Bayesian age–depth model and a reassessment of the chronologies for both already known and dated eruptive units and for so far undated eruptions. The results provide a significant contribution for improving knowledge on the peri-Tyrrhenian explosive activity as well as for extending the Mediterranean tephrostratigraphical framework, which was previously based on limited proximal and distal archives for that time interval.     

Asynchronous Geospatial Processing: An Event‐Driven Push‐Based Architecture for the OGC Web Processing Service

Geospatial processing tasks like solar potential analyses or floodplain investigations within flood scenarios are often complex and deal with large amounts of data. If such analysis operations are performed in distributed web‐based systems, technical capabilities are mostly not sufficient. Major shortcomings comprise the potentially long execution times and the vast amount of messaging overhead that arise from common poll‐based approaches. To overcome these issues, an approach for an event‐driven architecture for web‐based geospatial processing is proposed within this article. First, this article presents a thorough qualitative discussion of different available technologies for push‐based notifications. The aim of this discussion is to find the most suitable push‐based messaging technologies for application with OGC Web Processing Services (WPS). Based on this, an event‐driven architecture for asynchronous geospatial processing with the WPS is presented, building on the Web Socket Protocol as the transport protocol and the OGC Event Service as the message‐oriented middleware. The proposed architecture allows pushing notifications to clients once a task has completed. This paradigm enables the efficient execution of web‐based geospatial processing tasks as well as the integration of geographical analyses into event‐driven real‐time workflows.     

Determination of chlorophyll content of small water bodies (kettle holes) using hyperspectral airborne data

This study presents an approach for chlorophyll content determination of small shallow water bodies (kettle holes) from hyperspectral airborne ROSIS and HyMap data (acquired on 15 May and 29 July 2008 respectively). Investigated field and airborne spectra for almost all kettle holes do not correspond to each other due to differences in ground sampling distance. Field spectra were collected from the height of 30–35 cm (i.e. area of 0.01–0.015 m²). Airborne pixels of ROSIS and HyMap imageries cover an area of 4 m² and 16 m² respectively and their spectra are highly influenced by algae or bottom properties of the kettle holes. Analysis of airborne spectra revealed that chlorophyll absorption near 677 nm is the same for both datasets. In order to enhance absorption properties, both airborne hyperspectral datasets were normalized by the continuum removal approach. Linear regression algorithms for ROSIS and HyMap datasets were derived using normalized average chlorophyll absorption spectra for each kettle hole. Overall accuracy of biomass mapping for ROSIS data was 71%, and for HyMap 64%. Biomass mapping results showed that, depending on the type of kettle hole, algae distribution, the ‘packaging effect’ and bottom reflection lead to miscalculations of the chlorophyll content using hyperspectral airborne data.     

Local variations of solifluction activity and environment in the Abisko Mountains,Northern Sweden

Seven sites within the mountain region of Abisko, northern Sweden, were selected for measurement of solifluction movement rates and correlation with the local environmental factors. Grids with sizes from 20 m × 30 m to 50 m × 100 m included both solifluction landforms and adjacent ground. Positions of movement markers and the terrain were recorded and the grid areas were digitally reconstructed. This allowed topography, vegetation and soil texture (fraction of fine material) surfaces to be interpolated and used together with data on soil moisture in statistical analyses. Significant correlations differ from site to site indicating that environmental factors have varying importance and inter‐relations depending on the local setting. Geomorphic work was also assessed within the grids. The results indicate measurable geomorphic work where no landforms are present. These areas may make larger contributions to sediment displacement than where solifluction landforms exist. Solifluction is an important denudational agent in the region and has its greatest impact on landscape development in the western part of the region. Copyright © 2011 John Wiley & Sons, Ltd.     

Oligo-Miocene shearing along the Ailao Shan–Red River shear zone: Constraints from structural analysis and zircon U/Pb geochronology of magmatic rocks in the Diancang Shan massif, SE Tibet, China

The left-lateral strike-slip shearing along the Ailao Shan–Red River (ASRR) shear zone in the Southeastern Tibet, China, has been widely advocated to be a result of the Indian–Eurasian plate collision and post-collisional processes. The Diancang Shan (DCS) massif, which occurs at the northwestern extension of the Ailao Shan massif, is a typical high-grade metamorphic complex aligned along the ASRR tectonic belt. Structural and microstructural analysis of the plutonic intrusions in the DCS revealed different types of granitic intrusions spatially confined to the shear zone and temporally related to the left-lateral shearing along the ASRR shear zone in the DCS massif. The combined structural and geochronological results of SHRIMP-II and LA-ICP-MS zircon U/Pb isotopic dating have revealed successive magmatic intrusions and crystallization related to the Oligo-Miocene shearing in the DCS massif. The pre-, early- and syn-kinematic emplacements are linked to regional high-temperature deformation (lower amphibolite facies) at relatively deep crustal levels. The zircon U/Pb geochronological results suggest that the left-lateral ductile shearing along the ASRR shear zone was initiated at ca. 31 Ma, culminated between ca. 27 and 21 Ma resulting in high-temperature metamorphic conditions and slowed down at ca. 20 Ma at relatively low-temperatures.     

Radiocarbon age inversions and progression: source and causes in Late Holocene sediments from Lake Chapala,western Mexico

The results of eight radiocarbon datings of Lake Chapala sediments (site T46) are presented, the age inversions (AI) observed and their age progression discussed. As deduced from some AIs and the ²¹⁰Pb activity (site CHP4), the bioturbation zone in the lake varies over a depth of 5–25 cm. The linear sedimentation rates (LSRs) calculated from ¹⁴C ages do not match the LSR calculated from unsupported ²¹⁰Pb activity for the upper sediments. This demonstrates the usefulness of dating sediments with complementary radiometric techniques such as short-lived isotope counting (SLIC), i.e., ²¹⁰Pb and ¹³⁷Cs. This approach leads to the following conclusions: (1) The incorporation of detrital particles with ancient carbon into the sedimentary column of the lake occurred by a combination of: (a) the presence of outcrops of hydrothermal petroleum with ages >40 ka (ka = thousands of years) in the lake, and (b) mass transport due to the presence of two elongated gyre circulation patterns integrated by cyclonic circulation (counterclockwise) in the north portion of the lake and anticyclonic circulation in the southern part. (2) Consequently, the ¹⁴C ages of shallow lake sediments have geologic ages one order of magnitude greater compared to their ages determined by the ²¹⁰Pb method. (3) A bioturbation mechanism is not necessary to explain the ¹⁴C AI in the top 70 cm and from 110 to 150 cm depth of the sediments. (4) According to the biological proxies data for the last 600 years B.P., the paleoclimate at Lake Chapala has changed from sub-humid to dry environmental conditions, and eutrophication has increased over the past 100 years due to local input from ongoing agricultural activities.     

Comparing biodiversity between protected savanna and adjacent non-protected farmland in the southern Kalahari

In this study we investigated the effect of different land use options (wildlife versus livestock) on species richness of plants and reptiles in the protected Kgalagadi Transfrontier Park (KTP) versus adjacent non-protected farmland within the same savanna habitat type (Aoub dune veld) in the southern Kalahari, South Africa. Our results show that both plant and reptile species richness as well as plant cover and reptile abundance was significantly higher in the protected KTP than in the non-protected farmland. The higher proportion of shrub but lower proportions of perennial grass cover, herb cover, and herb species richness in the farmland can be explained by higher stocking rates and the differences in feeding behaviour between native wild ungulates (e.g. Antidorcas marsupialis, Oryx gazella) and livestock (mainly sheep). The reptile’s prey availability and microhabitats (perennial grass tussocks and rodent burrows) for thermoregulation and protection against predators were significantly lower in the farmland. To conclude, our results clearly show that long term effects of different land use options (wildlife in protected KTP versus extensive livestock production in the non-protected farmland) even within the same habitat type have led to significant changes in vegetation composition, availability of microhabitat structures and in the reptile community.     

Coronal Density Structures and CMEs: Superior Solar Conjunctions of Mars Express, Venus Express, and Rosetta: 2004, 2006, and 2008

Coronal radio-sounding experiments were carried out using the S-band (2.3 GHz) and X-band (8.4 GHz) signals of the ESA Mars Express, Venus Express, and Rosetta spacecraft during five superior conjunctions occurring in 2004, 2006 (3×), and 2008/2009. Differential frequency and propagation delay (ranging) observations were recorded during these opportunities over the better part of a solar cycle, yielding information on the large-scale structure of the coronal electron-density distribution and its variations, including fluctuations on time scales from seconds to hours. These results concern primarily regions of slow solar wind because the radio propagation path is generally confined to the low heliolatitude regions by the conjunction. The mean frequency fluctuation and total electron content are determined as a function of heliocentric distance, and, with a few exceptions caused by streamers and CMEs, are found to be consistent with previous results from experiments on Ulysses. Dense coronal streamers and several coronal mass ejection (CME) events were identified in the radio-frequency data, some of which were observed in white light by the LASCO coronagraphs onboard SOHO. For those events with sufficient mutual coverage, good correlations are found between the electron-content fluctuations and structure imaged by the LASCO instrument.     

The Runaway Weed: Costs and Failures of Phragmites australis Management in the USA

While public funding of invasive species management has increased substantially in the past decade, there have been few cross-institutional assessments of management programs. We assessed management of Phragmites australis, a problematic invader of coastal habitats, through a cross-institutional economic survey of 285 land managers from US public and private conservation organizations. We found that from 2005 to 2009, these organizations spent >$4.6 million per year on P. australis management, and that 94 % used herbicide to treat a total area of ～80,000 ha. Despite these high expenditures, few organizations accomplished their management objectives. There was no relationship between resources invested in management and management success, and those organizations that endorsed a particular objective were no more likely to achieve it. Our results question the efficacy of current P. australis management strategies and call for future monitoring of biological management outcomes.     

The rotations opening the Central and Northern Atlantic Ocean: compilation, drift lines, and flow lines

We provide an up-to-date compilation of Euler rotations that model the evolution of the Central and Northern Atlantic Ocean (Table 1). The data basis forms seafloor spreading magnetic anomalies of the Atlantic. We checked the published rotations and selected those that form a consistent model. The increments of the Euler rotations going back in time from magnetic anomaly to magnetic anomaly can be illustrated by chains of points on “drift lines” that are paths of motions from continent to continent. Along these paths, the continents bordering the Atlantic Ocean can be moved back to their Mesozoic position within Pangea. Other figures exhibit the early rifting of the North Atlantic, the drift of Iberia, and the evolution of the Greenland-Ellesmere region. The points on the drift lines do not correspond directly to the lines of magnetic anomalies or their “picks” displayed today symmetrically in the Atlantic Ocean. To acquire correspondence, symmetric “flow lines” are constructed analogous to the spreading procedure. But points on the flow lines constructed by half of the increments partially also deviate from the expected symmetric position and in this way quantify displacements or jumps of the axis of rifting or spreading. Most of the selected rotations are from the excellent analyses of previous work. Essential deviations from published rotations are the M 0 rotations of Eurasia and of the Porcupine unit with respect to North America (EUR-NAM and POR-NAM). They lead to a better coincidence between the back-rotated M 0 magnetic anomalies in the Bay of Biscay on the one side and a change of the first transform motions between Greenland and Svalbard on the other side. Through this explanation, an overlap in Pangea SW of Svalbard is avoided and transform motions instead of strong extension are predicted. Some additional data are needed to complete the model: the earliest part of the path of Iberia to North America (IBA-NAM) up to M 4 is calculated assuming that Iberia moved parallel to the African plate, though with slower spreading rates. The evolution of the Central and North Atlantic Ocean system is described in short. This model of the Central and North Atlantic was produced with the primary intention of clearing and fixing the positions of Africa, Iberia, and Eurasia as a framework for an improved reconstruction of the Western Tethys evolution.