Lizards and snakes from the late Miocene hominoid locality of Ravin de la Pluie (Axios Valley,Greece)

We here describe lizards and snakes from the late Miocene (MN 10) of Ravin de la Pluie, near Thessaloniki, Greece, a locality widely known for its hominoid primate Ouranopithecus macedoniensis. The new finds comprise two large-sized lizards (a probable anguine and a varanid) and two snakes (an elapid and a small-sized “colubrine”). Even if the material is represented by few specimens, this is the first record of squamates from the late Miocene MN 10 biozone of southeastern Europe and the third only for the whole continent. The importance of the varanid vertebrae for systematic attributions is discussed. The new varanid limb elements described herein rank among the few such specimens in the fossil record of monitor lizards. Judging from the new and previously published varanid appendicular material, we suggest that Neogene monitor lizards from Europe possessed comparatively short and robustly built limbs. Distinctive scars on one of the limb elements are interpreted as bite marks of a predator or scavenger, offering insights on the palaeoecology of the herpetofauna of the locality.     

Guest Editorial Latest developments in GIS/LIS

Abstract

Significant achievements have taken place in Geographical/Land Information Systems (GIS/LIS). An attempt is made to give an overview of the state of the art as well as a vision of progress still to be accomplished. Key issues are discussed in various GIS/LIS activities. A generic analysis shows that most of the applications are environment-oriented. The various GIS/LIS topical issues are discussed in the order of an ascending graph, including data capture, data structure and modelling, data quality and standards, institutions, ethics, education, visualization and interface, spatial decision support systems, and applications. Finally a brief assessment of the role and nature of GIS is made. It is noted, in particular, that there are great discrepancies in the spread and success of GIS/LIS at the international level. This is true between developed and developing countries, but the case can also be made between western industrialized countries. It is also observed that there is an increasing number of professions involved in GIS/LIS activities and an increasing collaboration between those professions. Finally, it is observed that GIS/LIS are used predominantly as a tool to manage and keep records, although there are signs that GIS/LIS are also leading the way towards a new spatial science. This is only a 1993 ‘snap shot’, and is expected that many of the statements have only a limited life, considering the rapid changes in both theory and technology.     

Distribution of deep carbon dioxide in relation to the structure and tectonic evolution of south-east France

Abstract

Throughout SE France, ¹³C-values of CO₂releases suggest that a variable part of the C0₂ emission derives from mantle and/or lower crust. Carbon dioxide emission takes place in various geological settings. Geodynamical analyses lead to the identification of five provinces: the Sub-Alpine Ranges, the French Massif Central, the Mediterranean part of the Languedoc, the western Pyrénées and the Alps at the West of the Penninic front. Possible correlations are suggested between CO₂ flux and tectonic history of the structural provinces.

Possible processes by which CO₂ is extracted from the mantle, stored and transferred to the surface are investigated for each of these provinces. Major crustal scale gas movements may have taken place during the Carboniferous (Variscan and Late Variscan tectogenesis), the Lias and Dogger (rifting), the Upper Cretaceous and the Cenozoic (Alpine tectogenesis), A model of successive circulations of fluids on the scale of the whole Southeastern France CO₂-belt is proposed. This integrated isotopic and geodynamic approach contributes to a better understanding of the regional CO₂flux.     

Shear behavior of geotextile-reinforced Chlef sand in the Mediterranean region: Laboratory investigation

Abstract

An experimental study about the effects of initial conditions of soil and geotextile reinforcement on the mechanical behavior of reinforced sand is presented in this paper. A series of direct shear tests are conducted on reconstituted specimens of dry and moist natural sand prepared with different initial water content (w?=?0, 1.5, 3, and 5%) and including the two arrangements of geotextile layers (one and two layers, respectively). Both S41 and PEC55types of non-woven geotextile were used and placed at different heights of the specimens to investigate the effect of geotextile reinforcement on the behavior of sand. Test specimens were prepared at Dr =80% of relative density and were subjected to three different normal stresses of 100, 200, and 300?kPa. The experimental results showed that the deposition mode (wet and dry) and the geotextile reinforcement have significant effects on the behavior of reinforced sand. The increase in shear strength is relatively more significant for specimens prepared with dry deposition mode as compared to those prepared with wet deposition mode and it increases with the number of geotextile layers, this effect becomes less significant for wet specimens. The experimental results also demonstrated that (PEC55) non-woven geotextile shows a better performance than the (S41) of geotextile. These results can be explained by the effective tensile strength property of polyester yarns of the (PEC55) non-woven geotextile that it has led to a significant increase in the shear strength.     

Cosmogenic Be dating of a sackung and its faulted rock glaciers, in the Alps of Savoy (France)

Sackungs are the largest gravitational deformation observed in mountains. They are characterized by the long-term slowness of the movements, but their mechanism is still not well understood. Nowadays cosmic ray exposure (CRE) dating methods allow dating the morphologic structures involved in sackung and can contribute at the understanding of their origin. In the Alps, the 5.3 km long Arcs sackung initiated during the activity of rock glaciers. Three samples from these faulted rock glaciers provide their first CRE ages and show that at 2000 m elevation these block accumulations moved during the Younger Dryas and stopped in early Holocene. Six ¹⁰Be ages of fault scarps show that the Arcs sackung lasted only a few thousand years and stopped at about 8462 ± 432 ¹⁰Be yr. They also reveal that deformation migrated upslope in agreement with a mechanism of flexural toppling of vertical layers. This unique and long gravitational event, characterized by migration of the deformation, does not support earthquake shaking as triggering mechanism for individual faults. It shows that, in the upper Isère valley, slope deformation was delayed of several thousand years after glacial debuttressing, and is not anymore active despite its fresh morphology.     

Olivine intergranular plasticity at mantle pressures and temperatures

The ductile behavior of olivine-rich rocks is critical to constrain thermal convection in the Earth's upper mantle. Classical olivine flow laws for dislocation or diffusion creep fail to explain the fast post-seismic surface displacements observed by GPS, which requires a much weaker lithosphere than predicted by classical laws. Here we compare the plasticity of olivine aggregates deformed experimentally at mantle pressures and temperatures to that of single crystals and demonstrate that, depending on conditions of stress and temperature, strain accommodated through grain-to-grain interactions – here called intergranular strain – can be orders of magnitude larger than intracrystalline strain, which significantly weakens olivine strength. This result, extrapolated along mantle geotherms, suggests that intergranular plasticity could be dominant in most of the upper mantle. Consequently, the strength of olivine-rich aggregates in the upper mantle may be significantly lower than predicted by flow laws based on intracrystalline plasticity models.     

Combining ECCI and FIB milling techniques to prepare site-specific TEM samples for crystal defect analysis of deformed minerals at high pressure

Dislocation microstructures in experimentally deformed single-crystal pyrope-rich garnet, (Mg,Fe)₃(Al,Cr)₃Si₃O₁₂, and polycrystalline forsterite, Mg₂SiO₄, were investigated by using electron channeling contrast imaging (ECCI) and transmission electron microscopy (TEM) combined with a focused ion beam (FIB)-microsampling. In the orientation-optimized ECCI method, we successfully observed individual dislocations across subgrain boundaries in a low-atomic-number mineral, pyrope-rich garnet (averaged Z-numbers, AZs ～ 10). Dislocations in a deformed forsterite (iron-free olivine) were also visible in the ECCI. In the ECCI on the single-crystal garnet, deformation bands consisting of dislocations, unusual contrasts in stripes and inhomogeneous distributions of sub-micrometer-sized pores were found. Further site-specific TEM observation on the deformation band revealed a high density of partial dislocations and stacking fault ribbons. The site-specific characterizations from ECCI to TEM, with assistance of FIB, can provide a new approach to investigate dislocation microstructures of deformed materials at high pressure and high temperature.     

Trace element geochemistry of K-rich impact spherules from howardites

The howardite–eucrite–diogenite (HED) achondrites are a group of meteorites that probably originate from the asteroid Vesta. Howardites are complex polymict breccias that sometimes contain, in addition to various rock debris, impact melt glasses which show an impressive range of compositions. In this paper we report on the geochemistry and O isotopes of a series of 6 Saharan polymict breccias (4 howardites and 2 polymict eucrites), and on the trace element abundances of high-K impact spherules found in two of them, Northwest Africa (NWA) 1664 and 1769, which are likely paired.The high-K impact spherules found in the howardites NWA 1664 and NWA 1769 display remarkable trace element patterns. Compared to eucrites or howardites, they all show prominent enrichments in Cs, Rb, K, Li and Ba, strong depletion in Na, while the REE and other refractory elements are unfractionated. These features could not have been generated during impact melting of their host howardites, nor other normal HED target materials. The involvement of Na-poor rocks, and possibly rocks of granitic composition, appears likely. Although these lithologies cannot be well constrained at present, our results demonstrate that the surface of Vesta is certainly more diverse than previously thought. Indeed, despite the large number of available HED meteorites (about 1000 different meteorites), the latter are probably not sufficient to describe the whole surface of their parent body.     

The main characteristics, problems, and prospects for Western European coastal seas

Located to the far West of Western Europe, France has a western maritime coastal zone of more than 3800 km, which is widely influenced by the North-eastern Atlantic. The English Channel, an epi-continental shallow sea with very strong tides, runs along 650 km of the French coast and 1100 km of the English coast. It is also a bio-geographical crossroad encompassing a much wider range of ecological conditions than other European seas. France's Atlantic coast north of the Gironde estuary is a succession of rocky and sandy shorelines, including a sizeable intertidal zone, a wide continental shelf, and two major estuaries (Loire and Gironde). South of the Gironde, the 260 km of coastline is low, sandy and straight, with a narrowing continental shelf further on South due to the presence of the Cape Breton canyon in the bathyal and abyssal zones. Interface between the continental and oceanic systems, these bordering seas--North Sea, English Channel and Atlantic Ocean--have been the subject of many recent research programmes (the European Mast-FLUXMANCHE and INTERREG programmes; the national coastal environment programme and the LITEAU programme in France), designed to improve comprehension of the functions, production, and dynamics of these seas as well as their future evolution. Given the many conflicting practices in these littoral zones, integrated coastal zone management appears to be essential in order to cope with both natural phenomena, such as the infilling of estuarine zones, cliff erosion, and rising sea levels, and chronic anthropogenic pressures, such as new harbour installations (container dikes, marinas), sea aggregate extraction for human constructions, and offshore wind mill farms. This article provides as complete an overview as possible of the research projects on these bordering seas, both those that have recently been accomplished and those that are currently in progress, in order to highlight the main characteristics of these ecosystems and to underline the future challenges for European marine research in terms of the integrated coastal zone management of these highly significant coastal zones.