Using ocean quahog (<Emphasis Type="Italic">Arctica islandica</Emphasis>) shells to reconstruct palaeoenvironment in Öresund,Kattegat and Skagerrak,Sweden

Shells of Arctica islandica collected between 1884 and 2004 from Öresund, Kattegat and Skagerrak (Swedish West Coast) were used to monitor local climate variations and the influence of human activities on the local environment. For this purpose, we analysed the growth, structure and chemical composition of these shells and compared them with shells collected from Kiel Bay, Norway and Iceland. The growth rate of the studied shells registers an NAO periodicity of ca 8 years. However, the observed signal is weak because of other environmental interferences that are either of natural or anthropogenic origin. For example, the oxygen isotope ratios show temperature fluctuation, but also the influx of low salinity water. Higher contents of S, N, Cu, Zn, As, Cd and P in shell portions formed during the last century are related to human activities such as mining and industrial development. Our study indicates that in order to use Arctica shells as archives of climate change it is necessary to study the full range of environmental data that is recorded in the shells by using a multi element and isotope approach in combination with different analytical techniques including investigation of growth rates and shell structure.     

Manoeuvring the middle ground: Social mobility and the renegotiation of gender and family obligations among Chinese Singaporeans

The article examines Singaporeans' experiences of upward social mobility and how traditional gender roles within the family are renegotiated and reinterpreted in Singapore. When the former British colony gained independence in 1965 its post-colonial government embarked on an ambitious modernization programme, under which villages were demolished and residents relocated to new high-rise estates, farmland gave way to factories, the education system was reformed, and women entered the workforce. The transformation has been accompanied by a rapid upward social mobility, whereby Singaporeans born in the midst of the transformation, in the period 1960s – 1980s, lived remarkably different lives compared with preceding generations. The article is an ethnographic analysis of how Singaporean middle-class women and men, who have experienced rapid upward social mobility, handle and negotiate changing expectations regarding gender and intergenerational support. The analytical framework is constructed around the concepts of social mobility, modernity, and spaces of contestation and negotiation. The ethnographic data illuminate how traditional family values, such as filial piety, are contested and renegotiated. The data also show how social mobility intersects with other forms of mobility, such as the spatial movement involved in urbanization. Women entering the labour force have to spend their days away from home and can no longer fully attend to their elderly family members and/or young children. However, spatial movement in the sense of increased access to transportation and communication has also enabled members of extended families to maintain their ‘urban kinship network’ without having to live together.     

Mechanical quality of bedrock with increasing ductile deformation

Most of the rocks in Precambrian shield areas have experienced a complex structural and metamorphic evolution, processes which have a strong influence on bedrock quality. The properties vary on both a local and a regional scale. It is highly beneficial to know the variations in detail when exploiting the rocks for industrial purposes. The main objective of the investigation was to study the variation of rock mechanical properties in an originally more or less isotropic rock at various stages of ductile deformation. The rocks investigated were Paleoproterozoic and with ages of ca. 1.80-1.88 Ga, and the areas chosen for sampling were situated north-east of Lake Vänern (Kristinehamn; 10 samples), south of the city of Eskilstuna, South Central Sweden (5 samples) and south of Ödeshög, near Lake Vättern in southern Sweden (7 samples). The 12 samples from the latter two areas are described in this investigation, while the 10 samples from Kristinehamn have been published earlier (Göransson et al., 2004). A comprehensive study of various parameters of importance for bedrock quality has been performed on all samples, e.g. studded tyre test (STT) and Los Angeles test (LA), uniaxial compressive strength (UCS), ultrasonic velocity, perimeter measurements of mineral phases, and petrographic and chemical analyses. The weakly deformed and massive (more or less isotropic) rocks show a tendency towards better properties of abrasion (STT) than the strongly deformed rocks and this can also be said for UCS, reflecting the greater ability of rocks to split along foliation planes. This is not entirely unambiguous, as the more deformed rocks, such as the mylonites, may have varying properties. This depends on the combined effects of, e.g. grain size, recrystallisation and foliation. However, the brittleness (LA) shows somewhat better values with increased deformation. This may depend on higher amounts of dark minerals, as their existence does not affect this test as much as in the case of abrasion tests. The perimeter values of the mineral phases display generally higher values, i.e. grain boundaries for the more strongly deformed rocks are more complicated. However, the values for the investigated mylonites may vary between low and high. The lower value may be due to dynamic recrystallisation and the creation of triple points (static recrystallisation) making the rock weaker. Besides, the development of a strong foliation may decrease rock strength despite the usually finer grain size. The results show that it is extremely important to consider all possible variations of bedrock before classification and exploitation, as the bedrock material in fact is highly heterogeneous.     

The influence of foliation on the fragility of granitic rocks, image analysis and quantitative microscopy

Fabric-dependent anisotropy is important in understanding the mechanical behaviour of foliated rocks because the foliation creates mechanically weak discontinuities. Using optical microscopy, a foliation index (FIX) was calculated for a group of granitic rocks in southern Sweden that displays a range of textures from foliated to nonfoliated. Image analysis from scanning electron microscope with backscattered detector (SEM/BSE) images was used in order to measure the rock texture of these samples. The analyses were compared with the Los Angeles (LA) test, which measures resistance of rock aggregate to fragmentation. The results demonstrate that the measured grain size, shape and spatial arrangement are important parameters controlling the fragility of the rock. Both the texture and foliation must be taken into account to obtain a significant relationship with the mechanical analyses. We suggest that this alternative method could be a helpful tool for predicting a rock's suitability as an aggregate as it gives a better understanding of the material properties compared to mechanical testing.