Ammonite-based correlations in the Cenomanian-lower Turonian of north-west Europe, central Tunisia and the Western Interior (North America)

The biochronology of Cenomanian-early Turonian ammonite faunas from three key stratotype areas (north-west Europe, central Tunisia and the Western Interior of North America) has been analysed and revised by utilizing the unitary association method. This review is prompted by the huge amount of biostratigraphic data published during recent decades and by a taxonomic homogenisation of the ammonite faunas from these key areas. The Cenomanian and lower Turonian of Tunisia comprise twenty-four Unitary Association zones and the middle Cenomanian-lower Turonian of the Western Interior Basin twenty-three such zones. The unitary association method means a two-fold increase in resolution of these ammonite zonations compared to the standard, empirical schemes. Central Tunisia and the Western Interior are correlated with north-west Europe by constructing a zonation including all taxa common to these areas. These correlations highlight the variable completeness and resolution of the faunal record through space and time, and reveal a significant number of diachronous taxa between the three areas. These correlations enable the designation of a new global marker for the middle/upper Cenomanian boundary, which is characterised by the disappearance of the genera Turrilites, Acanthoceras and Cunningtoniceras and by the appearance of Eucalycoceras, Pseudocalycoceras and Euomphaloceras. The only synchronous datum known is the last occurrence of Turrilites acutus, which may thus be used as a marker for the middle/upper Cenomanian boundary, provided that it does not turn out to be diachronous in the light of any new data.     

On the electrojet in South America

Summary The diurnal variation in the horizontal component (H) of south american stations under and close to the electrojet were plotted during the I.G.Y. Thus a dilatation towards the south of the electrojet in the western part of South America was inferred.

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Resumen Se graficó la variación diurna en la componente horizontal (H) de estaciones sudamericanas bajo y próximas al «electrojetra, durante el A.G.I. Estas sirvieron para inferir una dilatación hacia el sur del «electrojet» en el oeste de América del Sur.

     

Feintektonische Untersuchungen an Schlechten und Klüften in Steinkohlenflözen des Ruhrgebietes

Zusammenfassung Im Bereich des Gelsenkirchener Sattels und der Emscher Mulde wurden im Felde Neuessen der Hoesch A.G. in Altenessen feintektonische Untersuchungen angestellt mit dem Ziel, die Entstehung der Schlechten in der Kohle, insbesondere der bankschrägen t-Schlechten und der Klüfte im Nebengestein zu erklären.Auf Grund der Messungen in den Flözen der Bochumer und Essener Schichten wurden Diagramme nach SCHMIDT-SANDERs entworfen und ausgewertet. Getrennt nach steiler und flacher Lagerung worden die bankrechten - sowie die bankschrägen t-Schlechten mit ihren symmetrologischen Beziehungen genetisch gewertet. Bei der Übertragung vom Kleinbereich zur Großstruktur ließen sich Parallelen aufzeigen, die für eine einheitliche tektonische Beanspruchung des ganzen Ruhrgebietes sprechen durften.     

EUREKA industrial R&D projects for an improved environment

International collaboration is increasingly necessary in the field of environmental protection in relation to industrial research and development. The EUREKA initiative, launched in 1985, aims to increase industrial productivity and competitiveness in Europe by encouraging cross-border high technology research and development. The programme encompasses a number of ‘umbrella’ projects—EUROMAR, EUROCARE, EUROENVIRON, EUROTRAC and ENVINET. Each of these is designed to generate and support research and development projects. The paper gives examples of the projects and discusses the value of such large-scale international collaboration.     

Hazard map for volcanic ballistic impacts at Popocatépetl volcano (Mexico)

During volcanic explosions, volcanic ballistic projectiles (VBP) are frequently ejected. These projectiles represent a threat to people, infrastructure, vegetation, and aircraft due to their high temperatures and impact velocities. In order to protect people adequately, it is necessary to delimit the projectiles’ maximum range within well-defined explosion scenarios likely to occur in a particular volcano. In this study, a general methodology to delimit the hazard zones for VBP during volcanic eruptions is applied to Popocatépetl volcano. Three explosion scenarios with different intensities have been defined based on the past activity of the volcano and parameterized by considering the maximum kinetic energy associated with VBP ejected during previous eruptions. A ballistic model is used to reconstruct the “launching” kinetic energy of VBP observed in the field. In the case of Vulcanian eruptions, the most common type of activity at Popocatépetl, the ballistic model was used in concert with an eruptive model to correlate ballistic range with initial pressure and gas content, parameters that can be estimated by monitoring techniques. The results are validated with field data and video observations of different Vulcanian eruptions at Popocatépetl. For each scenario, the ballistic model is used to calculate the maximum range of VBP under optimum “launching” conditions: ballistic diameter, ejection angle, topography, and wind velocity. Our results are presented in the form of a VBP hazard map with topographic profiles that depict the likely maximum ranges of VBP under explosion scenarios defined specifically for Popocatépetl volcano. The hazard zones shown on the map allow the responsible authorities to plan the definition and mitigation of restricted areas during volcanic crises.     

Planform dynamics of the Iquitos anabranching structure in the Peruvian Upper Amazon River

The upper reach of the Amazon River has a very dynamic morphology, with the highest rates of migration observed in the entire Amazon River. It has an anabranching channel pattern which alternates between a condition of single channel and anabranching structures; in particular, the anabranching structure near Iquitos City shows an interesting channel behavior. Its channels migrate at different rates, where there are processes of narrowing and widening, and also collision and development of new channels. The temporal evolution of the Iquitos anabranching structure is described during the period from 1985 to 2014. The study is carried out by using satellite images to track the migration patterns, which are contrasted to the underlying geological units in the valley. Bathymetry of the structure and several velocity transects were obtained during a field campaign prior to the 2012 historic flood event. This information allowed for numerical modeling in order to compute the hydrodynamic flow field that complements the temporal analysis, aiming to understand the planform migration patterns after the 2012 flood event. It is observed that the geological units play an important role in modulating the migration rates and planform development of the channels. The channels in the structure are in contention to be the main channel, which become the secondary channel after migration. This causes the channels to experience a rise in bed elevation and narrowing of the channel itself; if this trend continues for several more years, these channels will detach from the Iquitos anabranching structure, thus forming paleo‐channels. This geomorphic process is important for horizontal and vertical soil heterogeneity along the floodplain. In general, the analysis shows a complex interaction between the underlying geological units, flow structure, morphology of the bed and planform migration. Copyright © 2016 John Wiley & Sons, Ltd.     

Seismic safety assessment of existing masonry infill structures in Nepal

Reinforced concrete (RC) buildings in Nepal are constructed with RC frames and masonry infill panels. These structures exhibit a highly non-linear inelastic behavior resulting from the interaction between the panels and frames. This paper presents an extensive case study of existing RC buildings in Nepal. Non-linear analyses were performed on structural models of the buildings considered as a bare frame and with masonry infill, in order to evaluate the influence of infill walls on the failure mechanisms. Five three-storey buildings with different structural configurations and detailing were selected. The effect of masonry infill panels on structural response was delineated by comparing the bare-framed response with the infill response. Seismic performance is evaluated with regard to global strength, stiffness, energy dissipation, inter-storey drift, and total deflection of the structure. A parametric analysis of structures with masonry infill is also performed. For this, the influence of different material properties is studied, namely diagonal compressive stress, modulus of elasticity and tensile stress of masonry infill panels. Study results show that masonry infill increases the global strength and stiffness of the structures; it decreases the inter-storey drift and hence the total displacement of the structure. The results quantify the influence of the infill panels on structural response and, in particular, the effect of the diagonal compressive strength of the masonry wall.     

Isotopic fingerprints on lacustrine organic matter from Laguna Potrok Aike (southern Patagonia, Argentina) reflect environmental changes during the last 16,000 years

A combination of carbon-to-nitrogen ratios (TOC/TN), Rock Eval-analyses, and stable isotope values of bulk nitrogen (δ¹⁵N) and organic carbon (δ¹³C_org) was used to characterize bulk organic matter (OM) of a piston core from the Patagonian maar lake Laguna Potrok Aike (Argentina) for the purpose of palaeoenvironmental reconstruction. Sedimentary data were compared with geochemical signatures of potential OM sources from Laguna Potrok Aike and its catchment area to identify the sources of sedimentary OM. Correlation patterns between isotopic data and TOC/TN ratios allowed differentiation of five distinct phases with different OM composition. Before 8470 calibrated ¹⁴C years before present (cal. yrs BP) and after 7400 cal. yrs BP, isotopic and organo-geochemical fingerprints indicate that the sediments of Laguna Potrok Aike consist predominantly of soil and diatom OM with varying admixtures of cyanobacterial and aquatic macrophyte OM. For a short phase of the early Holocene (ca. 8470–7400 cal. yrs BP), however, extremely high input of soil OM is implied by isotopic fingerprints. Previous seismic and geochronological results indicate a severe lake-level drop of 33 m below present-day shortly before 6590 cal. yrs BP. It is suggested that this lake level drop was accompanied by increased erosion of shore banks and channel incision enhancing soil OM deposition in the lake basin. Thus, isotopic data can be linked to hydrological variations at Laguna Potrok Aike and allow a more precise dating of this extremely low lake level. An isotopic mixing model was used including four different sources (soil, cyanobacteria, diatom and aquatic macrophyte OM) to model OM variations and the model results were compared with quantitative microfossil data.     

Late Holocene climate and environment of the SE Pampa grasslands,Argentina, inferred from biological indicators in shallow,freshwater Lake Nahuel Rucá

We analyzed pollen, non-pollen palynomorphs (NPPs), calcareous microfossils, plant macrofossils, diatoms, chrysophyte cysts, opal phytoliths and organic matter content in a 123-cm sediment sequence from Nahuel Rucá Lake, a shallow, freshwater system in the southeastern Pampa grasslands, Argentina. Three stages in the lake evolution were identified. Before 3,680 cal year BP, only pollen, NPPs (dinoflagellate cysts and acritarchs) and ostracods were recovered, suggesting brackish/saline conditions in the lake and nearby areas. Freshwater conditions are, however, indicated by Myriophyllum, Pediastrum and Zygnemataceae. The brackish/saline conditions could have been caused by marine influence during a Holocene sea level high stand that affected the area ca. 6,000 year BP. Between 3,680 and 390 cal year BP, macrophyte pollen and plant macrofossils indicate increasingly freshwater conditions in the lake and the adjacent area. Diatom and ostracod assemblages, however, suggest brackish and oligotrophic conditions, giving way to freshwater and meso-eutrophic conditions toward the end of this period. The relationship between submersed macrophytes (Myriophyllum, Potamogeton, Ceratophyllum, Chara) and planktonic algae (Chlorophyta and diatoms), suggests a shift in the lake from a clear to a turbid state. This turbid state is more evident after 390 cal year BP. High values of Pediastrum, Scenedesmus and diatoms (Cyclotella meneghiniana, Aulacoseira granulata, A. muzzanensis) observed during this stage could have reduced light penetration, with consequent loss of submersed plants. Pollen and plant macrofossils in the uppermost 20 cm indicate a shallow, freshwater lake similar to present, though an increase in brackish/freshwater diatoms suggests an increase in salinity, perhaps related to periodic droughts. Opal phytoliths yield a regional paleoclimatic reconstruction that agrees closely with inferences made using pollen, mammals and sediment characteristics.