Monte-Carlo Simulations of Cosmic-ray and Internal Radiation Effects on ISOCAM on Board ISO

One of the main limitations to the sensitivity of the infrared camera ISOCAM on-board the Infrared Space Observatory (ISO) comes from responsivity variations and glitches caused by the impacts of charged particles in photo-detectors. Glitch rate measurements, glitch properties and removal methods have already been addressed during the first ISO detector workshop(Madrid, 1998) and published in a special issue of Experimental Astronomy. It appeared that glitch rate and most of glitch properties could be reproduced by Monte-Carlo simulations. This is very interesting in order to predict before launch the effect of charged particles in photo-detectors operated in space. This paper presents results of Monte-Carlo simulations of radiation effects on ISOCAM detectors. Glitch rates, spatial and energetic properties of glitches have been computed and are compared with measured values. This revised version was published online in July 2006 with corrections to the Cover Date.     

A 20 cm2 CCD mosaic camera for a dark matter search part I : Mechanics,optics and cryogeny

A 20cm ² CCD mosaic camera has been especially built to search for dark galactic halo objects by the gravitational microlensing effect. The sensitive area is made of 16 edge-buttable CCDs developped by Thomson-CTS, with 23×23 µm ² pixels. The 35 kg camera housing and mechanical equipment is presented. The associated electronics and data acquisition system are described in a separate paper. The camera resides at the focal plane of a 40 cm, f/10, Ferson reflector. The instrument has been in operation since December 1991 at the La Silla Observatory (ESO).     

The lacustrine microbial carbonate factory of the successive Lake Bonneville and Great Salt Lake,Utah, USA

The Bonneville Basin is a continental lacustrine system accommodating extensive microbial carbonate deposits corresponding to two distinct phases: the deep Lake Bonneville (30 000 to 11 500 ¹⁴C bp ) and the shallow Great Salt Lake (since 11 500 ¹⁴C bp ). A characterization of these microbial deposits and their associated sediments provides insights into their spatio‐temporal distribution patterns. The Bonneville phase preferentially displays vertical distribution of the microbial deposits resulting from high‐amplitude lake level variations. Due to the basin physiography, the microbial deposits were restricted to a narrow shoreline belt following Bonneville lake level variations. Carbonate production was more efficient during intervals of relative lake level stability as recorded by the formation of successive terraces. In contrast, the Great Salt Lake microbial deposits showed a great lateral distribution, linked to the modern flat bottom configuration. A low vertical distribution of the microbial deposits was the result of the shallow water depth combined with a low amplitude of lake level fluctuations. These younger microbial deposits display a higher diversity of fabrics and sizes. They are distributed along an extensive ‘shore to lake’ transect on a flat platform in relation to local and progressive accommodation space changes. Microbial deposits are temporally discontinuous throughout the lake history showing longer hiatuses during the Bonneville phase. The main parameters controlling the rate of carbonate production are related to the interaction between physical (kinetics of the mineral precipitation, lake water temperature and runoff), chemical (Ca²⁺, Mg²⁺ and HCO₃^? concentrations, Mg/Ca ratio, dilution and depletion) and/or biological (trophic) factors. The contrast in evolution of Lake Bonneville and Great Salt Lake microbial deposits during their lacustrine history leads to discussions on major chemical and climatic changes during this interval as well as the role of physiography. Furthermore, it provides novel insights into the composition, structure and formation of microbialite‐rich carbonate deposits under freshwater and hypersaline conditions.     

A network theory approach for a better understanding of overland flow connectivity

Hydrological connectivity describes the physical coupling (linkages) of different elements within a landscape regarding (sub‐) surface flows. A firm understanding of hydrological connectivity is important for catchment management applications, for example, habitat and species protection, and for flood resistance and resilience improvement. Thinking about (geomorphological) systems as networks can lead to new insights, which has also been recognized within the scientific community, seeing the recent increase in the use of network (graph) theory within the geosciences. Network theory supports the analysis and understanding of complex systems by providing data structures for modelling objects and their linkages, and a versatile toolbox to quantitatively appraise network structure and properties. The objective of this study was to characterize and quantify overland flow connectivity dynamics on hillslopes in a humid sub‐Mediterranean environment by using a combination of high‐resolution digital‐terrain models, overland flow sensors and a network approach. Results showed that there are significant differences between overland flow connectivity on agricultural areas and semi‐natural shrubs areas. Significant positive correlations between connectivity and precipitation characteristics were found. Significant negative correlations between connectivity and soil moisture were found, most likely because of soil water repellency and/or soil surface crusting. The combination of structural networks and dynamic networks for determining potential connectivity and actual connectivity proved a powerful tool for analysing overland flow connectivity. Copyright © 2016 John Wiley & Sons, Ltd.     

An Eocene magmatic belt across central Tibet: mantle subduction triggered by the Indian collision?

Mountain domes rising to ≈ 6600 m along Tibet's Tanggula range herald the Eocene intrusion of calcalkaline granites into terranes accreted much earlier. Together with coeval, cogenetic volcanics, such intrusives, which have similar crystallization and cooling ages, may be part of an ESE-trending belt cutting central Tibet in half. This magmatic belt may have marked a former northern boundary of the plateau, testifying to S-directed subduction of the Asian mantle. Such subduction would have developed soon after India's collision but long before the rise of the plateau's present rims, along one of central Tibet's Mesozoic sutures.     

Alpine tectonics in the Calabrian–Peloritan belt (southern Italy): New 40Ar/39Ar data in the Aspromonte Massif area

This study provides new ⁴⁰Ar/³⁹Ar geochronological constraints on the age of the Alpine tectonics in the Aspromonte Massif (southern part of the Calabrian–Peloritan belt). This massif exposes the upper units of the Calabride Complex which originated from the European continental margin. The Calabride Complex was incorporated in the Alpine orogenic wedge and then integrated into the Apennines and Maghrebides fold-and-thrust belts. Throughout the Calabride Complex there is evidence for a two stage tectonic history, which remains however rather poorly dated: Alpine nappe stacking is followed by extensional reworking along the former thrust contacts or along new detachment surfaces. Our new ages suggest that exhumation of the uppermost units, which accompanied nappe stacking, probably started at 45 Ma and that the deepest units were almost completely exhumed at 33 Ma. This kinematics probably corresponds to syn-orogenic extension while the end of exhumation is clearly related to the extensional tectonics dated at 28.6 Ma along detachment structures.Our geochronological data reveal a very short lag time between accretional and extensional processes in this part of the Mediterranean Alpine orogenic belt. The direction of extension, when the units are restored to their initial position (i.e. before the opening of the Western Mediterranean basins and the bending of the arc) is NNE–SSW. Such a direction does not fit with the eastward slab-retreat model generally put forward to explain extension in the Western Mediterranean. In contrast, we provide evidence for roughly N–S middle Oligocene extension in the accretionary prism, not previously described in this part of the Mediterranean domain.     

Tableau de répartition stratigraphique des Grands Foraminifères caractéristiques du Crétacé moyen de la région Méditerranéenne

Le Groupe de Travail Européen des Grands Foraminifères présente un tableau de répartition stratigraphique de 42 espèces bien définies du Crétacé moyen de la région méditerranéenne. La répartition stratigraphique proposée pour chaque espèce est fondée soit sur des propres observations soit sur des données de la littérature supprimer et est contrôlée par la présence d'Ammonites ou de Foraminifères planctoniques.A summarizing account is presented of the deliberations of the research group for Large Foraminifers of the IGCP Project “Mid-Cretaceous Events”. Large Foraminifers are of incontestable value for dating carbonate platform sequences owing to the absence of many other diagnostic groups of organísms. A table of stratigraphical distributions for 42 species is presented.     

Do landslides follow landslides? Insights in path dependency from a multi-temporal landslide inventory

Landslides are a major category of natural disasters, causing loss of lives, livelihoods and property. The critical roles played by triggering (such as extreme rainfall and earthquakes), and intrinsic factors (such as slope steepness, soil properties and lithology) have previously successfully been recognized and quantified using a variety of qualitative, quantitative and hybrid methods in a wide range of study sites. However, available data typically do not allow to investigate the effect that earlier landslides have on intrinsic factors and hence on follow-up landslides. Therefore, existing methods cannot account for the potentially complex susceptibility changes caused by landslide events. In this study, we used a substantially different alternative approach to shed light on the potential effect of earlier landslides using a multi-temporal dataset of landslide occurrence containing 17 time slices. Spatial overlap and the time interval between landslides play key roles in our work. We quantified the degree to which landslides preferentially occur in locations where landslides occurred previously, how long such an effect is noticeable, and how landslides are spatially associated over time. We also investigated whether overlap with previous landslides causes differences in landslide geometric properties. We found that overlap among landslides demonstrates a clear legacy effect (path dependency) that has influence on the landslide affected area. Landslides appear to cause greater susceptibility for follow-up landslides over a period of about 10  years. Follow-up landslides are on average larger and rounder than landslides that do not follow earlier slides. The effect of earlier landslides on follow-up landslides has implications for understanding of the landslides evolution and the assessment of landslide susceptibility.