Structure of grain boundaries in wet,synthetic polycrystalline,statically recrystallizing halite – evidence from cryo‐SEM observations

It is well known from nature and experiments that the presence of brine strongly affects the microstructural evolution and the mechanical and transport properties of halite. Existing interpretations of the grain boundary structure in deformed, wet, salt samples annealed statically at room temperature are based on indirect evidence from reflected light microscopy and conventional scanning electron microscopy. This paper presents direct observations of fluid‐filled grain boundaries using the cryogenic‐scanning electron microscope (cryo‐SEM) in which the grain boundary fluids were frozen before breaking the samples. The rapid cooling transforms the brine into two phases, i.e. ice and hydrohalite, which are easily recognized from characteristic segregation patterns. We studied samples of wet, synthetic, polycrystalline halite annealed under static conditions at room temperature. In coarse‐grained samples, fine‐scale segregation patterns were observed at the boundaries of the primary recrystallizing grains. These points indicate the existence of fluid films with a thickness in the range of 30 nm, but the finer scale structure of the fluid remains unknown. In fine‐grained samples, the distribution and reorganization of fluids with annealing time is recorded by the combination of contact healing and successive accumulation of fluids in triple junction tubes. The contact healing is attributed to the small initial grain size, such that the fluid film necks down by accumulating the fluids into previously existing triple junctions via neck growth. Electron backscatter diffraction measurements of both primary and secondary recrystallized grains indicate that they are euhedral, i.e. the grain growth morphology is controlled by the anisotropy of the grain boundary energy of the growing grain, which results in planar growth faces.     

Relationship between deformation bands and petroleum migration in an exhumed reservoir rock,Los Angeles Basin,California, USA

An oil‐bearing sandstone unit within the Monterey Formation is exposed in the Los Angeles Basin along the Newport‐Inglewood fault zone in southern California. The unit preserves structures, some original fluids, and cements that record the local history of deformation, fluid flow, and cementation. The structures include two types of deformation bands, which are cut by later bitumen veins and sandstone dikes. The bands formed by dilation and by shear. Both types strike on average parallel to the Newport‐Inglewood fault zone (317°–332°) and show variable dip angles and directions. Generally the older deformation bands are shallow, and the younger bands are steep. The earlier set includes a type of deformation band not previously described in other field examples. These are thin, planar zones of oil 1–2 mm thick sandwiched between parallel, carbonate‐cemented, positively weathering ribs. All other deformation bands appear to be oil‐free. The undeformed sandstone matrix also contains some hydrocarbons. The oil‐cored bands formed largely in opening mode, similar to dilation bands. The oil‐cored bands differ from previously described dilation bands in the degree of carbonate cementation (up to 36% by volume) and in that some exhibit evidence for plane‐parallel shear during formation. Given the mostly oil‐free bands and oil‐rich matrix, deformation bands must have formed largely before the bulk of petroleum migration and acted as semi‐permeable baffles. Oil‐cored bands provide field evidence for early migration of oil into a potential reservoir rock. We infer a hydrofracture mechanism, probably from petroleum leaking out of a stratigraphically lower overpressured reservoir. The deformation bands described here provide a potential field example of a mechanism inferred for petroleum migration in modern systems such as in the Gulf of Mexico.     

ARCHAEOLOGICAL DATA ANALYSIS AND FUZZY CLUSTERING

Cluster analysis is widely used in archaeological data analysis. Fuzzy clustering is a more modern technique than methods normally used by archaeologists and has not been much exploited. Applications that have been reported are sometimes unsatisfactory and usually do not exploit the ‘fuzziness’ of the procedure. After a brief review of the more common methods of cluster analysis, fuzzy ideas and fuzzy clustering are discussed. The method is applied to three data sets of different sizes and complexity, to illustrate particular aspects of, and problems in, application. Summarizing results is less easy than for more standard methods, but has the potential to reveal features of the data concealed by other methods.     

NATURE AND MICROSTRUCTURE OF GALLIC IMITATIONS OF SIGILLATA SLIPS FROM THE LA GRAUFESENQUE WORKSHOP*

The red glaze (slip) that characterizes the Terra Sigillata potteries greatly contributed to their success during the Roman period. The colour of the slip can in fact be partially explained by the microstructure (crystalline phases, grain sizes) and the physico‐chemistry (composition) of the ceramics. However, the precise process and the diffusion of this technique are still not fully known. In particular, we do not know yet how the production of sigillata took place in the south of Gaul, and the role that was played by the production under Italian influence (pre‐sigillata) preceding the first local sigillata. In this work, a combination of transmission electron microscopy (TEM) and X‐ray synchrotron diffraction techniques was used to study the microstructure of pre‐sigillata slips from the main southern Gaul workshop (La Graufesenque), in order to compare their characteristics with those of high‐quality sigillata. These first results seem to indicate that the antique potters chose clays adapted to their firing conditions and to the type of coating that they wanted to make. These productions cannot be described as an initial phase for the later sigillata production and, rather, seem to correspond to the intention of developing a specific type of pottery only inspired by the famous Italian sigillata forms.     

THE APPLICATION OF TIME‐OF‐FLIGHT SECONDARY ION MASS SPECTROMETRY (ToF‐SIMS) TO THE CHARACTERIZATION OF OPAQUE ANCIENT GLASSES*

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) has been used, for the first time, for the characterization of opaque ancient glasses. Isotope‐specific chemical imaging with sub‐micron resolution enabled the separate analysis of opacifiying inclusions and the surrounding glass matrix. Phase identification has been demonstrated and quantification of the matrix composition has been investigated by use of Corning Glass Standard B as a model. Trace element detection limits are typically in the range 0.5–5.0 ppm atomic—in favourable cases down to 0.01 ppm. For the analysis of inclusions in particular, this has the potential to provide new information of use in establishing provenance and trade routes by ‘fingerprinting’ as well as the investigation of manufacturing techniques, as demonstrated by comparisons between glasses and with EDX data from the same samples.     

Emprise et déprise de l'agriculture sur le territoire de l'est de l'Ontario de 1826 à 2006: la dimension environnementale

Agricultural land‐cover changes in Eastern Ontario from 1826 to 2006: environmental effects. Stormont, Dundas and Glengarry (SDG) counties, Eastern Ontario, are among the first areas in Ontario to welcome settlers. In 1784, they established themselves in a forested land where wetlands are very important. Today, a large part of the wetlands has disappeared, but the landscape is wooded, masking the radical changes that took place over the course of the last two centuries. Analysis of census data from 1826 to 2006 allows the reconstruction of the history of land‐cover changes. It reveals the nature and rates of change for which a first analysis is presented. Four periods are identified. First, agriculture conquers the land and establishes its dominance. A plateau is reached in 1891 as agriculture maintains its supremacy until 1941. Then, as fast as agriculture invaded land, it fades away until 1986 when agricultural land‐cover stops shrinking. The opening of forest for cultivation was relatively slow in SDG because of biophysical and socio‐economical conditions associated with an absence of growth of agricultural population. Deforestation and wetland drainage led to a degradation of agricultural life but resulted in consideration of the environment in agriculture. Today, wooded and agricultural land covers are more balanced and environmental effects less acute.     

Awake anon the tales of valour: the career of a war memorial in St. Catharines,Ontario

Memorials cultivate a common understanding of the past that is communicated through the celebration of select people, places or events. Because memorials are located in public space and crafted from time‐defeating materials, the process of commemoration is inherently political. Scholars have studied this process to discover the agendas that inform the ideological content of memorials, but rarely how this content is received by its audience. This question is especially pertinent when memorials outlast the generation and the ideology that created them. This study attempts an answer by exploring the career of one memorial: the monument in St. Catharines, Ontario, dedicated to Private Alexander Watson, a casualty of the Battle of Batoche (1885). It finds that the monument's significance was transformed by political, cultural and historiographical shifts. While its local audience has forgotten its specific message, its generic intent to honour fallen soldiers is still recognized.     

Spatial‐temporal patterns of snow cover in western Canada

Snow cover is often measured as snow‐water equivalent (SWE), which refers to the amount of water stored in a snow pack that would be available upon melting. Snow cover and SWE represent a source of local snow‐melt release, and are sensitive to regional and global atmospheric circulation, and changes in climate. Monitoring SWE using satellite‐based passive microwave radiometry has provided nearly three decades of continuous data for North America. The availability of spatially and temporally extensive SWE data enables a better understanding of the nature of space‐time trends in snow cover, changes in these trends and linking these trends to underlying landscape and terrain characteristics. To address these interests, we quantify the spatial pattern of SWE by applying a local measure of spatial autocorrelation to 25 years of mean February SWE derived from passive microwave retrievals. Using a method for characterizing the temporal trends in the spatial pattern of SWE, temporal trends and variability in spatial autocorrelation are quantified. Results indicate that within the Canadian Prairies, extreme values of SWE are becoming more spatially coherent, with potential impacts on water availability, and hazards such as flooding. These results also highlight the need for Canadian ecological management units that consider winter conditions.     

Resisting RAMSI: Intervention,Identity and Symbolism in Solomon Islands

ABSTRACT The Australian‐led Regional Assistance Mission to Solomon Islands (RAMSI) continues to enjoy high levels of approval amongst Solomon Islanders. However, this approval belies the existence of a minority, but nevertheless important, dissenting perspective, one which has mostly emanated from Malaitan quarters. How are we to interpret Malaitan expressions of opposition to RAMSI? While these dissenting voices can, in part, be seen through a lens of legal and economic rationality, Malaitan opposition to RAMSI must be properly located within a deeper tradition of Malaitan resistance to the imposition of alien and centralised authority. Malaitans have responded to the RAMSI intervention by invoking kastom as a symbol of difference, unity and resistance, just as they have done in the past. It is argued that resistance to RAMSI must be (re)interpreted as having fundamentally cultural and historical underpinnings. Resisting RAMSI is as much about asserting culture and identity as it is about money and power. This argument is drawn out through an historically contextualised analysis of contemporary articulations of Malaitan resistance. The voices examined come from the public statements of prominent Malaitans, the published manifesto of the Malaita Ma'asina Forum, and interviews with former members of the Malaita Eagle Force.